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2019 |
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| 1. | Chakraborty, Atlanta; Chandru, Vijay; Rao, M R A linear programming primer: From Fourier to Karmarkar Journal Article Annals of Operations Research, 2019. Abstract | BibTeX | Tags: Control and Optimisation | Links: @article{Chakraborty2019, title = {A linear programming primer: From Fourier to Karmarkar}, author = {Atlanta Chakraborty and Vijay Chandru and M. R. Rao}, url = {http://www.rbccps.org/wp-content/uploads/2019/03/Chakraborty2019_Article_ALinearProgrammingPrimerFromFo.pdf}, doi = {10.1007/s10479-019-03186-2}, year = {2019}, date = {2019-03-01}, journal = {Annals of Operations Research}, abstract = {The story of linear programming is one with all the elements of a grand historical drama. The original idea of testing if a polyhedron is non-empty by using a variable elimination to project down one dimension at a time until a tautology emerges dates back to a paper by Fourier in 1823. This gets re-invented in the 1930s by Motzkin. The real interest in linear programming happens during World War II when mathematicians ponder best ways of utilising resources at a time when they are constrained. The problem of optimising a linear function over a set of linear inequalities becomes the focus of the effort. Dantzig’s Simplex Method is announced and the Rand Corporation becomes a hot bed of computational mathematics. The range of applications of this modelling approach grows and the powerful machinery of numerical analysis and numerical linear algebra becomes a major driver for the advancement of computing machines. In the 1970s, constructs of theoretical computer science indicate that linear programming may in fact define the frontier of tractable problems that can be solved effectively on large instances. This raised a series of questions and answers: Is the Simplex Method a polynomial-time method and if not can we construct novel polynomial time methods, etc. And that is how the Ellipsoid Method from the Soviet Union and the Interior Point Method from Bell Labs make their way into this story as the heroics of Khachiyan and Karmarkar. We have called this paper a primer on linear programming since it only gives the reader a quick narrative of the grand historical drama. Hopefully it motivates a young reader to delve deeper and add another chapter.}, keywords = {Control and Optimisation}, pubstate = {published}, tppubtype = {article} } The story of linear programming is one with all the elements of a grand historical drama. The original idea of testing if a polyhedron is non-empty by using a variable elimination to project down one dimension at a time until a tautology emerges dates back to a paper by Fourier in 1823. This gets re-invented in the 1930s by Motzkin. The real interest in linear programming happens during World War II when mathematicians ponder best ways of utilising resources at a time when they are constrained. The problem of optimising a linear function over a set of linear inequalities becomes the focus of the effort. Dantzig’s Simplex Method is announced and the Rand Corporation becomes a hot bed of computational mathematics. The range of applications of this modelling approach grows and the powerful machinery of numerical analysis and numerical linear algebra becomes a major driver for the advancement of computing machines. In the 1970s, constructs of theoretical computer science indicate that linear programming may in fact define the frontier of tractable problems that can be solved effectively on large instances. This raised a series of questions and answers: Is the Simplex Method a polynomial-time method and if not can we construct novel polynomial time methods, etc. And that is how the Ellipsoid Method from the Soviet Union and the Interior Point Method from Bell Labs make their way into this story as the heroics of Khachiyan and Karmarkar. We have called this paper a primer on linear programming since it only gives the reader a quick narrative of the grand historical drama. Hopefully it motivates a young reader to delve deeper and add another chapter. |
| 2. | Karanjkar, Neha; Tejasvi, Poorna Chandra; Amrutur, Bharadwaj A simpy-based simulation testbed Presentation 18.04.2019. Abstract | BibTeX | Tags: Smart City | Links: @misc{Karanjkar2019, title = {A simpy-based simulation testbed }, author = {Neha Karanjkar and Poorna Chandra Tejasvi and Bharadwaj Amrutur}, doi = {10.1145/3302505.3312591}, year = {2019}, date = {2019-04-18}, abstract = {A real-time testbed that emulates a large number of IoT end-points generating traffic to the middleware/application layers can be used for debugging and performance evaluation of the smart-city software platforms prior to deployment. We propose an architecture for such a simulation testbed based on Python's SimPy library. The simulated IoT end-points communicate with the middleware in real-time and can also interact directly with each other and with a common shared environment. This makes the testbed particularly suited for modeling system-wide scenarios such as synchronized faults and power outages.}, keywords = {Smart City}, pubstate = {published}, tppubtype = {presentation} } A real-time testbed that emulates a large number of IoT end-points generating traffic to the middleware/application layers can be used for debugging and performance evaluation of the smart-city software platforms prior to deployment. We propose an architecture for such a simulation testbed based on Python's SimPy library. The simulated IoT end-points communicate with the middleware in real-time and can also interact directly with each other and with a common shared environment. This makes the testbed particularly suited for modeling system-wide scenarios such as synchronized faults and power outages. |
| 3. | Gayarthi, H; Gulhare, Siddhartha; Verma, Ashish Characteristics of stop and go wave in one dimensional interrupted pedestrian flow through narrow channel Journal Article Collective Dynamics, pp. A18:1-14, 2019. Abstract | BibTeX | Tags: The Kumbh Mela Experiment | Links: @article{Gayarthi2019, title = {Characteristics of stop and go wave in one dimensional interrupted pedestrian flow through narrow channel}, author = {H. Gayarthi and Siddhartha Gulhare and Ashish Verma}, url = {http://www.rbccps.org/wp-content/uploads/2019/05/34-296-1-PB.pdf}, doi = {10.17815/CD.2018.18}, year = {2019}, date = {2019-01-12}, journal = {Collective Dynamics}, pages = {A18:1-14}, abstract = {Pedestrian microscopic simulation models can aid crowd management only if they can reproduce the crowd behavior correctly. To calibrate and validate the model, it is important to understand crowd movement during various activities involved in mass gathering events. A common practice in such gathering is to hold attendees in waiting area in near corridors separated by crowd barriers before the event and allow entering the event only after a designated time. The crowd is released in small batches to avoid overcrowding inside. Long waiting hours, anger, excitement, competitive feeling etc. can make crowd aggressive during such entries. Crowd flow characteristics due to such behavior is difficult to recreate in pedestrian experimental studies in laboratory setting. This paper studied interrupted flow of such crowd through a narrow corridors made of strong railing channel inside a temple. Interrupted flow lead to formation of one dimensional stop and go waves. These stop and go waves were studied from the trajectory data. The average speed of waves propagating over longer distance were also estimated. The quantitative output from this study can be used to calibrate and validate simulation models of such activity during mass gathering events.}, keywords = {The Kumbh Mela Experiment}, pubstate = {published}, tppubtype = {article} } Pedestrian microscopic simulation models can aid crowd management only if they can reproduce the crowd behavior correctly. To calibrate and validate the model, it is important to understand crowd movement during various activities involved in mass gathering events. A common practice in such gathering is to hold attendees in waiting area in near corridors separated by crowd barriers before the event and allow entering the event only after a designated time. The crowd is released in small batches to avoid overcrowding inside. Long waiting hours, anger, excitement, competitive feeling etc. can make crowd aggressive during such entries. Crowd flow characteristics due to such behavior is difficult to recreate in pedestrian experimental studies in laboratory setting. This paper studied interrupted flow of such crowd through a narrow corridors made of strong railing channel inside a temple. Interrupted flow lead to formation of one dimensional stop and go waves. These stop and go waves were studied from the trajectory data. The average speed of waves propagating over longer distance were also estimated. The quantitative output from this study can be used to calibrate and validate simulation models of such activity during mass gathering events. |
| 4. | Dholakiya, Dhaivat; Bhattacharya, Shounak; Gunalan, Ajay; Singla, Abhik; Bhatnagar, Shalabh; Amrutur, Bharadwaj; Ghosal, Ashitava; Kolathaya, Shishir Design, development and experimental realization of a quadrupedal research platform: Stoch Journal Article arXiv: Computer Science, 2019. Abstract | BibTeX | Tags: Walking Robot | Links: @article{Dholakiya2019, title = {Design, development and experimental realization of a quadrupedal research platform: Stoch}, author = {Dhaivat Dholakiya and Shounak Bhattacharya and Ajay Gunalan and Abhik Singla and Shalabh Bhatnagar and Bharadwaj Amrutur and Ashitava Ghosal and Shishir Kolathaya}, url = {http://www.rbccps.org/wp-content/uploads/2019/05/1901.00697.pdf}, year = {2019}, date = {2019-01-03}, journal = {arXiv: Computer Science}, abstract = {In this paper, we present a complete description of the hardware design and control architecture of our custom built quadruped robot, called the `Stoch'. Our goal is to realize a robust, modular, and a reliable quadrupedal platform, using which various locomotion behaviors are explored. This platform enables us to explore different research problems in legged locomotion, which use both traditional and learning based techniques. We discuss the merits and limitations of the platform in terms of exploitation of available behaviours, fast rapid prototyping, reproduction and repair. Towards the end, we will demonstrate trotting, bounding behaviors, and preliminary results in turning. In addition, we will also show various gait transitions i.e., trot-to-turn and trot-to-bound behaviors. }, keywords = {Walking Robot}, pubstate = {published}, tppubtype = {article} } In this paper, we present a complete description of the hardware design and control architecture of our custom built quadruped robot, called the `Stoch'. Our goal is to realize a robust, modular, and a reliable quadrupedal platform, using which various locomotion behaviors are explored. This platform enables us to explore different research problems in legged locomotion, which use both traditional and learning based techniques. We discuss the merits and limitations of the platform in terms of exploitation of available behaviours, fast rapid prototyping, reproduction and repair. Towards the end, we will demonstrate trotting, bounding behaviors, and preliminary results in turning. In addition, we will also show various gait transitions i.e., trot-to-turn and trot-to-bound behaviors. |
| 5. | Suran, Swathi; Varma, Manoj Imaging flow distribution through nanoporous polymer films using bright-field nanoscopy Journal Article Journal of Applied Physics, 125 (16), pp. 165303:1-5, 2019. Abstract | BibTeX | Tags: Sensing and Actuation Systems | Links: @article{Suran2019, title = {Imaging flow distribution through nanoporous polymer films using bright-field nanoscopy }, author = {Swathi Suran and Manoj Varma}, url = {http://www.rbccps.org/wp-content/uploads/2019/05/1.5089278.pdf}, doi = {10.1063/1.5089278}, year = {2019}, date = {2019-04-23}, journal = {Journal of Applied Physics}, volume = {125}, number = {16}, pages = {165303:1-5}, abstract = {Bright-field nanoscopy (BFN), an optical visualization technique using standard diffraction-limited microscopy, has been used in the past to visualize nanoscale objects such as grain boundaries in single layer graphene and water transport across nanomembranes. Here, we show how BFN can be used to visualize and gather information about water transport networks in porous polymer membranes. We were able to visualize a sub-100 nm network of pores in a polyelectrolyte multilayer using this technique. The extracted pore diameter distribution fitted well to an exponential distribution. Further, the time evolution of pore diameter displayed two distinct regimes consistent with expectations.}, keywords = {Sensing and Actuation Systems}, pubstate = {published}, tppubtype = {article} } Bright-field nanoscopy (BFN), an optical visualization technique using standard diffraction-limited microscopy, has been used in the past to visualize nanoscale objects such as grain boundaries in single layer graphene and water transport across nanomembranes. Here, we show how BFN can be used to visualize and gather information about water transport networks in porous polymer membranes. We were able to visualize a sub-100 nm network of pores in a polyelectrolyte multilayer using this technique. The extracted pore diameter distribution fitted well to an exponential distribution. Further, the time evolution of pore diameter displayed two distinct regimes consistent with expectations. |
| 6. | Soundararajan, Rajiv; Biswas, Soma Machine vision quality assessment for robust face detection Journal Article Signal Processing: Image Communication, 72 , pp. 92-104, 2019. Abstract | BibTeX | Tags: Student Research Grant | Links: @article{Soundararajan2019, title = {Machine vision quality assessment for robust face detection}, author = {Rajiv Soundararajan and Soma Biswas}, url = {http://www.rbccps.org/wp-content/uploads/2019/05/1-s2.0-S0923596518306957-main.pdf}, doi = {10.1016/j.image.2018.12.012}, year = {2019}, date = {2019-03-29}, journal = {Signal Processing: Image Communication}, volume = {72}, pages = {92-104}, abstract = {Machine vision quality (MVQ) assessment for face detection refers to image quality as judged by face detection algorithms. While perceptual image quality usually depends on human observers, MVQ depends on factors such as the face detection algorithm and performance measures such as recall and precision. We define the MVQ index as a weighted combination of the predicted precision and recall of the face detection algorithm and predict it using image features based on natural scene statistics. A filter bank framework is developed to achieve image enhancement of distorted images for face detection, where the enhancement operations can be optimized for either perceptual quality or MVQ. It is shown that MVQ can be effectively used to control the relative performance of recall and precision that can be achieved on enhanced images. For certain face detection algorithms, optimizing for MVQ instead of perceptual quality can lead to improved face detection performance. The MVQ is developed for three different face detection algorithms and the image enhancement framework is tested on a dataset based on the IDEAL-LIVE Distorted Face Database. A computationally efficient method to optimize for MVQ is designed by predicting the MVQ of enhanced images directly from features extracted from distorted images and filter parameters. The optimization framework is further enhanced by allowing for filter bank independent optimization of MVQ.}, keywords = {Student Research Grant}, pubstate = {published}, tppubtype = {article} } Machine vision quality (MVQ) assessment for face detection refers to image quality as judged by face detection algorithms. While perceptual image quality usually depends on human observers, MVQ depends on factors such as the face detection algorithm and performance measures such as recall and precision. We define the MVQ index as a weighted combination of the predicted precision and recall of the face detection algorithm and predict it using image features based on natural scene statistics. A filter bank framework is developed to achieve image enhancement of distorted images for face detection, where the enhancement operations can be optimized for either perceptual quality or MVQ. It is shown that MVQ can be effectively used to control the relative performance of recall and precision that can be achieved on enhanced images. For certain face detection algorithms, optimizing for MVQ instead of perceptual quality can lead to improved face detection performance. The MVQ is developed for three different face detection algorithms and the image enhancement framework is tested on a dataset based on the IDEAL-LIVE Distorted Face Database. A computationally efficient method to optimize for MVQ is designed by predicting the MVQ of enhanced images directly from features extracted from distorted images and filter parameters. The optimization framework is further enhanced by allowing for filter bank independent optimization of MVQ. |
| 7. | Prasanth, V; Parekhji, Rubin; Amrutur, Bharadwaj Perturbation based workload augmentation for comprehensive functional safety analysis Conference Forthcoming Proceedings of the 32nd International Conference on VLSI Design and 18th International Conference on Embedded Systems, 05.-09.01.19, New Delhi, Forthcoming. BibTeX | Tags: Electrical Communications Engineering @conference{Prasanth2019, title = {Perturbation based workload augmentation for comprehensive functional safety analysis}, author = {V. Prasanth and Rubin Parekhji and Bharadwaj Amrutur}, year = {2019}, date = {2019-01-09}, booktitle = {Proceedings of the 32nd International Conference on VLSI Design and 18th International Conference on Embedded Systems, 05.-09.01.19, New Delhi}, keywords = {Electrical Communications Engineering}, pubstate = {forthcoming}, tppubtype = {conference} } |
| 8. | Nayak, Ashika; Kundu, Atreyee Stabilizing switching signals for discrete-time switched linear systems: A unifying framework Conference Forthcoming Proceedings of the Fifth Indian Control Conference (ICC), 09.-11.01.19, New Delhi, Forthcoming. BibTeX | Tags: Control and Optimisation @conference{Nayak2019, title = {Stabilizing switching signals for discrete-time switched linear systems: A unifying framework}, author = {Ashika Nayak and Atreyee Kundu}, year = {2019}, date = {2019-01-11}, booktitle = {Proceedings of the Fifth Indian Control Conference (ICC), 09.-11.01.19, New Delhi}, keywords = {Control and Optimisation}, pubstate = {forthcoming}, tppubtype = {conference} } |
2018 |
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| 9. | Ramaswamy, Arunselvan; Bhatnagar, Shalabh Analysis of gradient descent methods with nondiminishing bounded errors Journal Article IEEE Transactions on Automatic Control, 63 (5), pp. 1465-1471, 2018. Abstract | BibTeX | Tags: Control and Optimisation | Links: @article{Ramaswamy2018, title = { Analysis of gradient descent methods with nondiminishing bounded errors}, author = {Arunselvan Ramaswamy and Shalabh Bhatnagar}, url = {http://www.rbccps.org/wp-content/uploads/2018/08/08016343.pdf}, doi = {10.1109/TAC.2017.2744598}, year = {2018}, date = {2018-05-31}, journal = {IEEE Transactions on Automatic Control}, volume = {63}, number = {5}, pages = {1465-1471}, abstract = {The main aim of this paper is to provide an analysis of gradient descent (GD) algorithms with gradient errors that do not necessarily vanish, asymptotically. In particular, sufficient conditions are presented for both stability (almost sure boundedness of the iterates) and convergence of GD with bounded (possibly) nondiminishing gradient errors. In addition to ensuring stability, such an algorithm is shown to converge to a small neighborhood of the minimum set, which depends on the gradient errors. It is worth noting that the main result of this paper can be used to show that GD with asymptotically vanishing errors indeed converges to the minimum set. The results presented herein are not only more general when compared to previous results, but our analysis of GD with errors is new to the literature to the best of our knowledge. Our work extends the contributions of Mangasarian and Solodov, Bertsekas and Tsitsiklis, and Tadiόand Doucet. Using our framework, a simple yet effective implementation of GD using simultaneous perturbation stochastic approximations, with constant sensitivity parameters, is presented. Another important improvement over many previous results is that there are no “additional” restrictions imposed on the step sizes. In machine learning applications where step sizes are related to learning rates, our assumptions, unlike those of other papers, do not affect these learning rates. Finally, we present experimental results to validate our theory.}, keywords = {Control and Optimisation}, pubstate = {published}, tppubtype = {article} } The main aim of this paper is to provide an analysis of gradient descent (GD) algorithms with gradient errors that do not necessarily vanish, asymptotically. In particular, sufficient conditions are presented for both stability (almost sure boundedness of the iterates) and convergence of GD with bounded (possibly) nondiminishing gradient errors. In addition to ensuring stability, such an algorithm is shown to converge to a small neighborhood of the minimum set, which depends on the gradient errors. It is worth noting that the main result of this paper can be used to show that GD with asymptotically vanishing errors indeed converges to the minimum set. The results presented herein are not only more general when compared to previous results, but our analysis of GD with errors is new to the literature to the best of our knowledge. Our work extends the contributions of Mangasarian and Solodov, Bertsekas and Tsitsiklis, and Tadiόand Doucet. Using our framework, a simple yet effective implementation of GD using simultaneous perturbation stochastic approximations, with constant sensitivity parameters, is presented. Another important improvement over many previous results is that there are no “additional” restrictions imposed on the step sizes. In machine learning applications where step sizes are related to learning rates, our assumptions, unlike those of other papers, do not affect these learning rates. Finally, we present experimental results to validate our theory. |
| 10. | Krishnapuram, Raghu; Rajkumar, Arun; Acharya, Adithya; Dhara, Nikhil; Goudar, Manjunath; Sarashetti, Akshay P Online domain adaptation by exploiting labeled features and pro-active learning Conference Proceedings of the 2018 ACM India Joint International Conference on Data Science and Management of Data (CoDS-COMAD), 11.-13.01.18, Goa, 2018. Abstract | BibTeX | Tags: Machine Learning | Links: @conference{Krishnapuram2018, title = { Online domain adaptation by exploiting labeled features and pro-active learning}, author = {Raghu Krishnapuram and Arun Rajkumar and Adithya Acharya and Nikhil Dhara and Manjunath Goudar and Akshay P. Sarashetti}, url = {http://www.rbccps.org/wp-content/uploads/2018/08/p137-krishnapuram.pdf}, doi = {10.1145/3152494.3152507}, year = {2018}, date = {2018-01-13}, booktitle = {Proceedings of the 2018 ACM India Joint International Conference on Data Science and Management of Data (CoDS-COMAD), 11.-13.01.18, Goa}, pages = {137-145}, abstract = {Domain adaptation algorithms have gained considerable interest in recent years due to their empirical success. However, most of the existing literature assumes the availability of a pool of unlabeled target domain data which is not the case in several practical scenarios. We consider the problem of online domain adaptation where the target (test) data arrives one at a time, and there is a fixed budget available for obtaining their labels. We propose a novel online domain adaptation algorithm which uses the budget judiciously by balancing the cost and reliability of the oracles which provide the labels. The proposed algorithm uses a probabilistic model which allows the seamless integration of previously unseen features (i.e., features that may appear during test time) into the model. Experiments on several benchmark real world datasets empirically establish the efficacy of the proposed algorithm.}, keywords = {Machine Learning}, pubstate = {published}, tppubtype = {conference} } Domain adaptation algorithms have gained considerable interest in recent years due to their empirical success. However, most of the existing literature assumes the availability of a pool of unlabeled target domain data which is not the case in several practical scenarios. We consider the problem of online domain adaptation where the target (test) data arrives one at a time, and there is a fixed budget available for obtaining their labels. We propose a novel online domain adaptation algorithm which uses the budget judiciously by balancing the cost and reliability of the oracles which provide the labels. The proposed algorithm uses a probabilistic model which allows the seamless integration of previously unseen features (i.e., features that may appear during test time) into the model. Experiments on several benchmark real world datasets empirically establish the efficacy of the proposed algorithm. |
| 11. | Naveen, K P; Sundaresan, Rajesh A double-auction mechanism for mobile data-offloading markets with strategic agents Conference Proceedings of the 16th International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks (WiOpt), 07.-11.05.18, Shanghai (China), 2018. Abstract | BibTeX | Tags: Electrical Communications Engineering | Links: @conference{Naveen2018, title = {A double-auction mechanism for mobile data-offloading markets with strategic agents}, author = {K. P. Naveen and Rajesh Sundaresan}, url = {http://www.rbccps.org/wp-content/uploads/2018/12/08362857.pdf}, doi = {10.23919/WIOPT.2018.8362857}, year = {2018}, date = {2018-05-24}, booktitle = {Proceedings of the 16th International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks (WiOpt), 07.-11.05.18, Shanghai (China)}, abstract = {We consider a recently proposed double-auction mechanism for mobile data-offloading. Network operators (users) derive benefit from offloading their traffic to third party WiFi or femtocell network (link-supplier). A link-supplier experiences costs for the additional capacity that he provides. Users and link-supplier (collectively referred to as agents) have their utilities and cost function as private knowledge. A system-designer decomposes the problem into a network problem (with surrogate utilities and surrogate cost functions) and agent problems (one per agent). The surrogate utilities and cost functions are modulated by the agents' bids. Agents' payoffs and costs are then determined by the allocations and prices set by the system designer. So long as the agents do not anticipate the effect of their actions, a competitive equilibrium exists as a solution to the network and agent problems, and this equilibrium optimizes the system utility. This work shows that when the agents are strategic (price-anticipating), the presence of strategic supplying agents drives the system to an undesirable equilibrium with zero participation. This is in stark contrast to the setting when link-suppliers are not strategic where the efficiency loss is at most 34%. The paper then proposes a Stackelberg game modification to alleviate the efficiency loss problem. The system designer first announces the allocation and payment functions. He then invites the supplying agents to announce their bids. He then invites the users to respond to the suppliers' bids. The resulting efficiency loss is characterized in terms of the suppliers' cost functions.}, keywords = {Electrical Communications Engineering}, pubstate = {published}, tppubtype = {conference} } We consider a recently proposed double-auction mechanism for mobile data-offloading. Network operators (users) derive benefit from offloading their traffic to third party WiFi or femtocell network (link-supplier). A link-supplier experiences costs for the additional capacity that he provides. Users and link-supplier (collectively referred to as agents) have their utilities and cost function as private knowledge. A system-designer decomposes the problem into a network problem (with surrogate utilities and surrogate cost functions) and agent problems (one per agent). The surrogate utilities and cost functions are modulated by the agents' bids. Agents' payoffs and costs are then determined by the allocations and prices set by the system designer. So long as the agents do not anticipate the effect of their actions, a competitive equilibrium exists as a solution to the network and agent problems, and this equilibrium optimizes the system utility. This work shows that when the agents are strategic (price-anticipating), the presence of strategic supplying agents drives the system to an undesirable equilibrium with zero participation. This is in stark contrast to the setting when link-suppliers are not strategic where the efficiency loss is at most 34%. The paper then proposes a Stackelberg game modification to alleviate the efficiency loss problem. The system designer first announces the allocation and payment functions. He then invites the supplying agents to announce their bids. He then invites the users to respond to the suppliers' bids. The resulting efficiency loss is characterized in terms of the suppliers' cost functions. |
| 12. | Lakshminarayanan, Chandrashekar; Bhatnagar, Shalabh; Szepesvári, Csaba A linearly relaxed approximate linear program for Markov decision processes Journal Article IEEE Transactions on Automatic Control, 63 (4), pp. 1185-1191, 2018. Abstract | BibTeX | Tags: Control and Optimisation | Links: @article{Lakshminarayanan2018, title = {A linearly relaxed approximate linear program for Markov decision processes}, author = {Chandrashekar Lakshminarayanan and Shalabh Bhatnagar and Csaba Szepesvári}, url = {http://www.rbccps.org/wp-content/uploads/2018/08/08014469.pdf}, doi = {10.1109/TAC.2017.2743163}, year = {2018}, date = {2018-04-30}, journal = {IEEE Transactions on Automatic Control}, volume = {63}, number = {4}, pages = {1185-1191}, abstract = {Approximate linear programming (ALP) and its variants have been widely applied to Markov decision processes (MDPs) with a large number of states. A serious limitation of ALP is that it has an intractable number of constraints, as a result of which constraint approximations are of interest. In this paper, we define a linearly relaxed approximation linear program (LRALP) that has a tractable number of constraints, obtained as positive linear combinations of the original constraints of the ALP. The main contribution is a novel performance bound for LRALP.}, keywords = {Control and Optimisation}, pubstate = {published}, tppubtype = {article} } Approximate linear programming (ALP) and its variants have been widely applied to Markov decision processes (MDPs) with a large number of states. A serious limitation of ALP is that it has an intractable number of constraints, as a result of which constraint approximations are of interest. In this paper, we define a linearly relaxed approximation linear program (LRALP) that has a tractable number of constraints, obtained as positive linear combinations of the original constraints of the ALP. The main contribution is a novel performance bound for LRALP. |
| 13. | Raseena, K T; Ghosh, Prasanta Kumar A maximum likelihood formulation to exploit heart rate variability for robust heart rate estimation from facial video Conference Proceedings of the 40th International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), 18.-21.07., Honolulu (USA), 2018. Abstract | BibTeX | Tags: Student Research Grant | Links: @conference{Raseena2018, title = {A maximum likelihood formulation to exploit heart rate variability for robust heart rate estimation from facial video}, author = {K. T. Raseena and Prasanta Kumar Ghosh}, url = {http://www.rbccps.org/wp-content/uploads/2018/12/08513483.pdf}, doi = {10.1109/EMBC.2018.8513483}, year = {2018}, date = {2018-10-29}, booktitle = {Proceedings of the 40th International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), 18.-21.07., Honolulu (USA)}, abstract = {The problem of estimating the heart rate (HR) from a facial video is considered. A typical approach for this problem is to use independent component analysis (ICA) on the red, blue, green intensity profiles averaged over the facial region. This provides estimates of the underlying source signals, whose spectral peaks are used to predict HR in every analysis window. In this work, we propose a maximum likelihood formulation to optimally select a source signal in each window such that the predicted HR trajectory not only corresponds to the most likely spectral peaks but also ensures a realistic HR variability (HRV) across analysis windows. The likelihood function is efficiently optimized using dynamic programming in a manner similar to Viterbi decoding. The proposed scheme for HR estimation is denoted by vICA. The performance of vICA is compared with a typical ICA approach as well as a recently proposed sparse spectral peak tracking (SSPT) technique that ensures that the predicted HR does not vary drastically across analysis windows. Experiments are performed in a five fold setup using facial videos of 15 subjects recorded using two types of smartphones (Samsung Galaxy and iPhone) at three different distances (6inches, 1foot, 2feet) between the phone camera and the subject. Mean absolute error (MAE) between the original and predicted HR reveals that the proposed vICA scheme performs better than the best of the baseline schemes, namely SSPT by -8.69%, 52.77% and 8.00% when Samsung Galaxy phone was used at a distance of 6inches, 1foot, and 2feet respectively. These improvements are 12.13%, 13.59% and 18.34% when iPhone was used. This, in turn, suggests that the HR predicted from a facial video becomes more accurate when the smoothness of HRV is utilized in predicting the HR trajectory as done in the proposed vICA.}, keywords = {Student Research Grant}, pubstate = {published}, tppubtype = {conference} } The problem of estimating the heart rate (HR) from a facial video is considered. A typical approach for this problem is to use independent component analysis (ICA) on the red, blue, green intensity profiles averaged over the facial region. This provides estimates of the underlying source signals, whose spectral peaks are used to predict HR in every analysis window. In this work, we propose a maximum likelihood formulation to optimally select a source signal in each window such that the predicted HR trajectory not only corresponds to the most likely spectral peaks but also ensures a realistic HR variability (HRV) across analysis windows. The likelihood function is efficiently optimized using dynamic programming in a manner similar to Viterbi decoding. The proposed scheme for HR estimation is denoted by vICA. The performance of vICA is compared with a typical ICA approach as well as a recently proposed sparse spectral peak tracking (SSPT) technique that ensures that the predicted HR does not vary drastically across analysis windows. Experiments are performed in a five fold setup using facial videos of 15 subjects recorded using two types of smartphones (Samsung Galaxy and iPhone) at three different distances (6inches, 1foot, 2feet) between the phone camera and the subject. Mean absolute error (MAE) between the original and predicted HR reveals that the proposed vICA scheme performs better than the best of the baseline schemes, namely SSPT by -8.69%, 52.77% and 8.00% when Samsung Galaxy phone was used at a distance of 6inches, 1foot, and 2feet respectively. These improvements are 12.13%, 13.59% and 18.34% when iPhone was used. This, in turn, suggests that the HR predicted from a facial video becomes more accurate when the smoothness of HRV is utilized in predicting the HR trajectory as done in the proposed vICA. |
| 14. | Chakrabortty, Tuhin; Suman, Akash; Gupta, Anjali; Singh, Varsha; Varma, Manoj A null-model exhibiting synchronized dynamics in uncoupled oscillators Journal Article arXiv: Physics, 2018. Abstract | BibTeX | Tags: Robot swarms | Links: @article{Chakrabortty2018, title = {A null-model exhibiting synchronized dynamics in uncoupled oscillators}, author = {Tuhin Chakrabortty and Akash Suman and Anjali Gupta and Varsha Singh and Manoj Varma}, url = {http://www.rbccps.org/wp-content/uploads/2018/12/1811.03781.pdf}, year = {2018}, date = {2018-11-12}, journal = {arXiv: Physics}, abstract = {The phenomenon of phase synchronization of oscillatory systems arising out of feedback coupling is ubiquitous across physics and biology. In noisy, complex systems, one generally observes transient epochs of synchronization followed by non-synchronous dynamics. How does one guarantee that the observed transient epochs of synchronization are arising from an underlying feedback mechanism and not from some peculiar statistical properties of the system? This question is particularly important for complex biological systems where the search for a non-existent feedback mechanism may turn out be an enormous waste of resources. In this article, we propose a null model for synchronization motivated by expectations on the dynamical behaviour of biological systems to provide a quantitative measure of the confidence with which one can infer the existence of a feedback mechanism based on observation of transient synchronized behaviour. We demonstrate the application of our null model to the phenomenon of gait synchronization in free-swimming nematodes, C. elegans. }, keywords = {Robot swarms}, pubstate = {published}, tppubtype = {article} } The phenomenon of phase synchronization of oscillatory systems arising out of feedback coupling is ubiquitous across physics and biology. In noisy, complex systems, one generally observes transient epochs of synchronization followed by non-synchronous dynamics. How does one guarantee that the observed transient epochs of synchronization are arising from an underlying feedback mechanism and not from some peculiar statistical properties of the system? This question is particularly important for complex biological systems where the search for a non-existent feedback mechanism may turn out be an enormous waste of resources. In this article, we propose a null model for synchronization motivated by expectations on the dynamical behaviour of biological systems to provide a quantitative measure of the confidence with which one can infer the existence of a feedback mechanism based on observation of transient synchronized behaviour. We demonstrate the application of our null model to the phenomenon of gait synchronization in free-swimming nematodes, C. elegans. |
| 15. | Karanjkar, Neha; Desai, Madhav; Bhatnagar, Shalabh A simulation-based technique for continuous-space embedding of discrete-parameter queueing systems Conference Forthcoming Proceedings of the 32nd European Simulation and Modelling Conference (ESM), 24.-26.10.18, Ghent (Belgium), Forthcoming. Abstract | BibTeX | Tags: Control and Optimisation @conference{Karanjkar2018b, title = {A simulation-based technique for continuous-space embedding of discrete-parameter queueing systems}, author = {Neha Karanjkar and Madhav Desai and Shalabh Bhatnagar}, year = {2018}, date = {2018-10-26}, booktitle = {Proceedings of the 32nd European Simulation and Modelling Conference (ESM), 24.-26.10.18, Ghent (Belgium)}, abstract = {This paper presents a simulation-based technique for embedding the discrete-valued parameters in queuing systems (such as buffer capacities) into a continuous space. The significance of this technique is that it enables the direct application of existing descent-based continuous optimizers for solving simulation optimization problems efficiently over a discrete parameter set. The embedding technique is based on a randomization of the simulation model itself, and is applicable when the objective function is a long-run average measure. Unlike spatial interpolation, the computational cost of this embedding is independent of the number of parameters in the system, making the approach well-suited to high-dimensional problems. We present a theoretical basis for this embedding technique and demonstrate its utility in the optimization of discrete-time queuing systems.}, keywords = {Control and Optimisation}, pubstate = {forthcoming}, tppubtype = {conference} } This paper presents a simulation-based technique for embedding the discrete-valued parameters in queuing systems (such as buffer capacities) into a continuous space. The significance of this technique is that it enables the direct application of existing descent-based continuous optimizers for solving simulation optimization problems efficiently over a discrete parameter set. The embedding technique is based on a randomization of the simulation model itself, and is applicable when the objective function is a long-run average measure. Unlike spatial interpolation, the computational cost of this embedding is independent of the number of parameters in the system, making the approach well-suited to high-dimensional problems. We present a theoretical basis for this embedding technique and demonstrate its utility in the optimization of discrete-time queuing systems. |
| 16. | Joglekar, Ashish; Rawat, Alok; Rajaraman, Vasanth; Amrutur, Bharadwaj; Mony, Prem; Thankachan, Prashanth; Raj, Tony; Rao, Suman A wearable sensor for monitoring Kangaroo Mother Care for premature neonates Conference Forthcoming Proceedings of the IEEE Sensors 2018 Conference, 28.-31.10.18, New Delhi, Forthcoming. BibTeX | Tags: Remote Neonatal Monitoring and Intervention @conference{Joglekar2018, title = {A wearable sensor for monitoring Kangaroo Mother Care for premature neonates}, author = {Ashish Joglekar and Alok Rawat and Vasanth Rajaraman and Bharadwaj Amrutur and Prem Mony and Prashanth Thankachan and Tony Raj and Suman Rao}, year = {2018}, date = {2018-10-31}, booktitle = {Proceedings of the IEEE Sensors 2018 Conference, 28.-31.10.18, New Delhi}, keywords = {Remote Neonatal Monitoring and Intervention}, pubstate = {forthcoming}, tppubtype = {conference} } |
| 17. | Bansal, Sahil; Ghosh, Anindita; Seelamantula, Chandra Sekhar; Gurrala, Gurunath; Ghosh, Prasanta Kumar Adaptive frequency estimation using iterative DESA with RDFT-based filter Conference Proceedings of the 2017 IEEE PES Asia-Pacific Power and Energy Engineering Conference (APPEEC), 08.-10.11.17, Bangalore, 2018. Abstract | BibTeX | Tags: Smart Grid | Links: @conference{Bansal2018, title = {Adaptive frequency estimation using iterative DESA with RDFT-based filter}, author = {Sahil Bansal and Anindita Ghosh and Chandra Sekhar Seelamantula and Gurunath Gurrala and Prasanta Kumar Ghosh}, url = {http://www.rbccps.org/wp-content/uploads/2018/12/08308990.pdf}, doi = {10.1109/APPEEC.2017.8308990}, year = {2018}, date = {2018-03-08}, booktitle = {Proceedings of the 2017 IEEE PES Asia-Pacific Power and Energy Engineering Conference (APPEEC), 08.-10.11.17, Bangalore}, abstract = {This paper proposes a new approach for estimating fundamental frequency of grid signals. The approach is based on a discrete-time energy separation algorithm (DESA) combined with an adaptive bandpass filter (BPF). The BPF is built using a discrete Fourier transform (DFT) and inverse DFT both used recursively. The technique is computationally efficient and robust to the harmonics and noise in the signal. The method's performance is validated by comparing the results with some existing algorithms.}, keywords = {Smart Grid}, pubstate = {published}, tppubtype = {conference} } This paper proposes a new approach for estimating fundamental frequency of grid signals. The approach is based on a discrete-time energy separation algorithm (DESA) combined with an adaptive bandpass filter (BPF). The BPF is built using a discrete Fourier transform (DFT) and inverse DFT both used recursively. The technique is computationally efficient and robust to the harmonics and noise in the signal. The method's performance is validated by comparing the results with some existing algorithms. |
| 18. | Akhil, P T; Sundaresan, Rajesh Algorithms for separable convex optimization with linear ascending constraints Journal Article Sādhanā, 2018. Abstract | BibTeX | Tags: Electrical Communications Engineering | Links: @article{Akhil2018, title = {Algorithms for separable convex optimization with linear ascending constraints}, author = {P. T. Akhil and Rajesh Sundaresan}, url = {http://www.rbccps.org/wp-content/uploads/2018/12/Akhil-Sundaresan2018_Article_AlgorithmsForSeparableConvexOp.pdf}, doi = {10.1007/s12046-018-0890-2}, year = {2018}, date = {2018-09-28}, journal = {Sādhanā}, abstract = {The paper considers the minimization of a separable convex function subject to linear ascending constraints. The problem arises as the core optimization in several resource allocation scenarios, and is a special case of an optimization of a separable convex function over the bases of a polymatroid with a certain structure. The paper generalizes a prior algorithm to a wider class of separable convex objective functions that need not be smooth or strictly convex. The paper also summarizes the state-of-the-art algorithms that solve this optimization problem. When the objective function is a so-called ?-separable function, a simpler linear time algorithm solves the problem.}, keywords = {Electrical Communications Engineering}, pubstate = {published}, tppubtype = {article} } The paper considers the minimization of a separable convex function subject to linear ascending constraints. The problem arises as the core optimization in several resource allocation scenarios, and is a special case of an optimization of a separable convex function over the bases of a polymatroid with a certain structure. The paper generalizes a prior algorithm to a wider class of separable convex objective functions that need not be smooth or strictly convex. The paper also summarizes the state-of-the-art algorithms that solve this optimization problem. When the objective function is a so-called ?-separable function, a simpler linear time algorithm solves the problem. |
| 19. | Arjun, N; Ashwin, S M; Polachan, Kurian; Prabhakar, T V; Singh, Chandramani An end to end tactile cyber physical system design Conference Proceedings of the 4th International Workshop on Emerging Ideas and Trends in the Engineering of Cyber-Physical Systems (EITEC), 11.04.18, Porto (Portugal), 2018. Abstract | BibTeX | Tags: Student Research Grant | Links: @conference{Arjun2018, title = {An end to end tactile cyber physical system design}, author = {N. Arjun and S. M. Ashwin and Kurian Polachan and T. V. Prabhakar and Chandramani Singh}, url = {http://www.rbccps.org/wp-content/uploads/2018/12/08400299.pdf}, doi = {10.1109/EITEC.2018.00007}, year = {2018}, date = {2018-07-02}, booktitle = {Proceedings of the 4th International Workshop on Emerging Ideas and Trends in the Engineering of Cyber-Physical Systems (EITEC), 11.04.18, Porto (Portugal)}, abstract = {We describe design and implementation of an end to end Tactile Cyber Physical System (TCPS). We begin with proposing a generic architecture for TCPSs. We then describe a typical system in which a robotic arm at one end of the network replicates the posture of a human hand at the other end with a tactile glove. For the human operator end, we design a tactile glove having Inertial Measurement Unit (IMU) sensors for motion capture and vibrotactile actuators for tactile feedback. On the teleoperator end, we use a PhantomX reactor robotic arm with force sensors and design an inverse kinematic engine for this. We also provide a mechanism for visual feedback using a USB camera on the teleoperator end. We describe in detail the hardware and software designs of the tactile glove and the controller board for the robot. We also detail the industrial design of the tactile glove. We perform detail experiments to characterize the tactile glove, robotic arm and round-trip delay of the TCPS implementation.}, keywords = {Student Research Grant}, pubstate = {published}, tppubtype = {conference} } We describe design and implementation of an end to end Tactile Cyber Physical System (TCPS). We begin with proposing a generic architecture for TCPSs. We then describe a typical system in which a robotic arm at one end of the network replicates the posture of a human hand at the other end with a tactile glove. For the human operator end, we design a tactile glove having Inertial Measurement Unit (IMU) sensors for motion capture and vibrotactile actuators for tactile feedback. On the teleoperator end, we use a PhantomX reactor robotic arm with force sensors and design an inverse kinematic engine for this. We also provide a mechanism for visual feedback using a USB camera on the teleoperator end. We describe in detail the hardware and software designs of the tactile glove and the controller board for the robot. We also detail the industrial design of the tactile glove. We perform detail experiments to characterize the tactile glove, robotic arm and round-trip delay of the TCPS implementation. |
| 20. | Joseph, Ajin George; Bhatnagar, Shalabh An online prediction algorithm for reinforcement learning with linear function approximation using cross entropy method Journal Article arXiv: Computer Science, 2018. Abstract | BibTeX | Tags: Machine Learning | Links: @article{Joseph2018, title = {An online prediction algorithm for reinforcement learning with linear function approximation using cross entropy method}, author = {Ajin George Joseph and Shalabh Bhatnagar}, url = {http://www.rbccps.org/wp-content/uploads/2018/12/1806.06720.pdf}, year = {2018}, date = {2018-06-15}, journal = {arXiv: Computer Science}, abstract = {In this paper, we provide two new stable online algorithms for the problem of prediction in reinforcement learning, emph{i.e.}, estimating the value function of a model-free Markov reward process using the linear function approximation architecture and with memory and computation costs scaling quadratically in the size of the feature set. The algorithms employ the multi-timescale stochastic approximation variant of the very popular cross entropy (CE) optimization method which is a model based search method to find the global optimum of a real-valued function. A proof of convergence of the algorithms using the ODE method is provided. We supplement our theoretical results with experimental comparisons. The algorithms achieve good performance fairly consistently on many RL benchmark problems with regards to computational efficiency, accuracy and stability. }, keywords = {Machine Learning}, pubstate = {published}, tppubtype = {article} } In this paper, we provide two new stable online algorithms for the problem of prediction in reinforcement learning, emph{i.e.}, estimating the value function of a model-free Markov reward process using the linear function approximation architecture and with memory and computation costs scaling quadratically in the size of the feature set. The algorithms employ the multi-timescale stochastic approximation variant of the very popular cross entropy (CE) optimization method which is a model based search method to find the global optimum of a real-valued function. A proof of convergence of the algorithms using the ODE method is provided. We supplement our theoretical results with experimental comparisons. The algorithms achieve good performance fairly consistently on many RL benchmark problems with regards to computational efficiency, accuracy and stability. |
| 21. | Kallatt, Sangeeth; Nair, Smitha; Majumdar, Kausik Asymmetrically encapsulated vertical ITO/MoS2/Cu2O photodetector with ultrahigh sensitivity Journal Article Small: Micro and Nano, 14 (3), pp. 1-7, 2018. Abstract | BibTeX | Tags: Photonics | Links: @article{Kallatt2018, title = {Asymmetrically encapsulated vertical ITO/MoS2/Cu2O photodetector with ultrahigh sensitivity }, author = {Sangeeth Kallatt and Smitha Nair and Kausik Majumdar}, url = {http://www.rbccps.org/wp-content/uploads/2018/08/Kallatt_et_al-2018-Small.pdf}, doi = {10.1002/smll.201702066}, year = {2018}, date = {2018-01-31}, journal = {Small: Micro and Nano}, volume = {14}, number = {3}, pages = {1-7}, abstract = {Strong light absorption, coupled with moderate carrier transport properties, makes 2D layered transition metal dichalcogenide semiconductors promising candidates for low intensity photodetection applications. However, the performance of these devices is severely bottlenecked by slow response with persistent photocurrent due to long lived charge trapping, and nonreliable characteristics due to undesirable ambience and substrate effects. Here ultrahigh specific detectivity (D*) of 3.2 × 10^14 Jones and responsivity (R) of 5.77 × 10^4 A W^−1 are demonstrated at an optical power density (Pop) of 0.26 W m^−2 and external bias (Vext) of −0.5 V in an indium tin oxide/MoS2/copper oxide/Au vertical multi‐heterojunction photodetector exhibiting small carrier transit time. The active MoS2 layer being encapsulated by carrier collection layers allows us to achieve repeatable characteristics over large number of cycles with negligible trap assisted persistent photocurrent. A large D* > 10^14 Jones at zero external bias is also achieved due to the built‐in field of the asymmetric photodetector. Benchmarking the performance against existing reports in literature shows a viable pathway for achieving reliable and highly sensitive photodetectors for ultralow intensity photodetection applications. }, keywords = {Photonics}, pubstate = {published}, tppubtype = {article} } Strong light absorption, coupled with moderate carrier transport properties, makes 2D layered transition metal dichalcogenide semiconductors promising candidates for low intensity photodetection applications. However, the performance of these devices is severely bottlenecked by slow response with persistent photocurrent due to long lived charge trapping, and nonreliable characteristics due to undesirable ambience and substrate effects. Here ultrahigh specific detectivity (D*) of 3.2 × 10^14 Jones and responsivity (R) of 5.77 × 10^4 A W^−1 are demonstrated at an optical power density (Pop) of 0.26 W m^−2 and external bias (Vext) of −0.5 V in an indium tin oxide/MoS2/copper oxide/Au vertical multi‐heterojunction photodetector exhibiting small carrier transit time. The active MoS2 layer being encapsulated by carrier collection layers allows us to achieve repeatable characteristics over large number of cycles with negligible trap assisted persistent photocurrent. A large D* > 10^14 Jones at zero external bias is also achieved due to the built‐in field of the asymmetric photodetector. Benchmarking the performance against existing reports in literature shows a viable pathway for achieving reliable and highly sensitive photodetectors for ultralow intensity photodetection applications. |
| 22. | Navaneet, K L; Mandikal, Priyanka; Agarwal, Mayank; Babu, Venkatesh R CAPNet: Continuous approximation projection for 3D point cloud reconstruction using 2D supervision Journal Article arXiv: Computer Science, 2018. Abstract | BibTeX | Tags: Student Research Grant | Links: @article{Navaneet2018, title = {CAPNet: Continuous approximation projection for 3D point cloud reconstruction using 2D supervision}, author = {K. L. Navaneet and Priyanka Mandikal and Mayank Agarwal and R. Venkatesh Babu}, url = {http://www.rbccps.org/wp-content/uploads/2018/12/1811.11731.pdf}, year = {2018}, date = {2018-11-28}, journal = {arXiv: Computer Science}, abstract = {Knowledge of 3D properties of objects is a necessity in order to build effective computer vision systems. However, lack of large scale 3D datasets can be a major constraint for data-driven approaches in learning such properties. We consider the task of single image 3D point cloud reconstruction, and aim to utilize multiple foreground masks as our supervisory data to alleviate the need for large scale 3D datasets. A novel differentiable projection module, called 'CAPNet', is introduced to obtain such 2D masks from a predicted 3D point cloud. The key idea is to model the projections as a continuous approximation of the points in the point cloud. To overcome the challenges of sparse projection maps, we propose a loss formulation termed 'affinity loss' to generate outlier-free reconstructions. We significantly outperform the existing projection based approaches on a large-scale synthetic dataset. We show the utility and generalizability of such a 2D supervised approach through experiments on a real-world dataset, where lack of 3D data can be a serious concern. To further enhance the reconstructions, we also propose a test stage optimization procedure to obtain reconstructions that display high correspondence with the observed input image. }, keywords = {Student Research Grant}, pubstate = {published}, tppubtype = {article} } Knowledge of 3D properties of objects is a necessity in order to build effective computer vision systems. However, lack of large scale 3D datasets can be a major constraint for data-driven approaches in learning such properties. We consider the task of single image 3D point cloud reconstruction, and aim to utilize multiple foreground masks as our supervisory data to alleviate the need for large scale 3D datasets. A novel differentiable projection module, called 'CAPNet', is introduced to obtain such 2D masks from a predicted 3D point cloud. The key idea is to model the projections as a continuous approximation of the points in the point cloud. To overcome the challenges of sparse projection maps, we propose a loss formulation termed 'affinity loss' to generate outlier-free reconstructions. We significantly outperform the existing projection based approaches on a large-scale synthetic dataset. We show the utility and generalizability of such a 2D supervised approach through experiments on a real-world dataset, where lack of 3D data can be a serious concern. To further enhance the reconstructions, we also propose a test stage optimization procedure to obtain reconstructions that display high correspondence with the observed input image. |
| 23. | Gulhare, Siddhartha; Verma, Ashish; Chakroborty, Partha Comparison of pedestrian data of single file movement collected from controlled pedestrian experiment and from field in mass religious gathering Journal Article Collective Dynamics, 3 , pp. A16: 1-14, 2018. Abstract | BibTeX | Tags: The Kumbh Mela Experiment | Links: @article{Gulhare2018, title = {Comparison of pedestrian data of single file movement collected from controlled pedestrian experiment and from field in mass religious gathering}, author = {Siddhartha Gulhare and Ashish Verma and Partha Chakroborty}, url = {http://www.rbccps.org/wp-content/uploads/2018/08/27-278-1-PB.pdf}, doi = {10.17815/CD.2018.16}, year = {2018}, date = {2018-05-04}, journal = {Collective Dynamics}, volume = {3}, pages = {A16: 1-14}, abstract = {Managing and controlling crowd during mass religious gathering is a challenge for organizers. With good computational capabilities, it is possible to create tools to simulate crowd in real time to aid crowd management. These tools need to be first calibrated and validated with pedestrian empirical data. The empirical data collection from field is difficult and therefore, data collection through controlled pedestrian experiments have become a convenient substitute. However, the ability of experiment data to reproduce actual crowd behavior needs to be examined. This study compared the experiment data with field data collected from mass religious gathering named Kumbh Mela held in India, 2016. The single file movement (pedestrians moving along a single line; SFM) experiment was conducted and its results were compared with the field SFM results. The speed in the field was found to be generally higher than in the experiment for a given density. The results clearly indicate that the pedestrians in the field are motivated to achieve a purpose but participants in the experiments lack the motivation. The pedestrian dynamics of the experiment was found to be different from the field. Hence, the results of pedestrian experiments should not be extrapolated to understand panic, crowd risk situations.}, keywords = {The Kumbh Mela Experiment}, pubstate = {published}, tppubtype = {article} } Managing and controlling crowd during mass religious gathering is a challenge for organizers. With good computational capabilities, it is possible to create tools to simulate crowd in real time to aid crowd management. These tools need to be first calibrated and validated with pedestrian empirical data. The empirical data collection from field is difficult and therefore, data collection through controlled pedestrian experiments have become a convenient substitute. However, the ability of experiment data to reproduce actual crowd behavior needs to be examined. This study compared the experiment data with field data collected from mass religious gathering named Kumbh Mela held in India, 2016. The single file movement (pedestrians moving along a single line; SFM) experiment was conducted and its results were compared with the field SFM results. The speed in the field was found to be generally higher than in the experiment for a given density. The results clearly indicate that the pedestrians in the field are motivated to achieve a purpose but participants in the experiments lack the motivation. The pedestrian dynamics of the experiment was found to be different from the field. Hence, the results of pedestrian experiments should not be extrapolated to understand panic, crowd risk situations. |
| 24. | Rao, Suman; Thankachan, Prashanth; Amrutur, Bharadwaj; Washington, Maryann; Mony, Prem Continuous, real-time monitoring of neonatal position and temperature during Kangaroo Mother Care using a wearable sensor: A techno-feasibility pilot study Journal Article Pilot and Feasibility Studies, 99 (4), pp. 1-7, 2018. Abstract | BibTeX | Tags: Remote Neonatal Monitoring and Intervention | Links: @article{Rao2018, title = {Continuous, real-time monitoring of neonatal position and temperature during Kangaroo Mother Care using a wearable sensor: A techno-feasibility pilot study}, author = {Suman Rao and Prashanth Thankachan and Bharadwaj Amrutur and Maryann Washington and Prem Mony}, url = {http://www.rbccps.org/wp-content/uploads/2018/06/Rao_et_al-2018-Pilot_and_Feasibility_Studies.pdf}, doi = {10.1186/s40814-018-0293-5}, year = {2018}, date = {2018-05-21}, journal = {Pilot and Feasibility Studies}, volume = {99}, number = {4}, pages = {1-7}, abstract = {Background: Remote biomonitoring of vital parameters in hospitals and homes has the potential to improve coverage and quality of maternal and neonatal health. Wearable sensors coupled with modern information and communication technology now offer an opportunity to monitor temperatures and kangaroo mother care (KMC) adherence in a continuous and real-time manner remotely for several days’ duration in hospital and home settings. Using an innovative remote biomonitoring device to measure both temperature and baby position, we undertook a techno-feasibility study in preparation for a clinical trial. Methods: We designed and developed a wearable sensor for tracking KMC adherence and neonatal temperature, using social innovation design principles. After screening mother-infant dyads using clinical and logistic eligibility criteria, we piloted this wearable sensor along with a gateway device and the commercial cellular network. The dyads were recruited during hospitalization and followed up in the hospital and home phases for several days. Simple descriptive statistical analysis was undertaken. Results: Recruitment rate was 50% (6/12), and consenting rate was 83% (5/6) during a 2-month period. These five neonates contributed a total of 39 study days (15 hospital days and 24 home days). Their mean [± standard deviation (S.D.)] birth weight was 1490 (± 244) g. The mean (± S.D.) of the vital signs for the five babies was temperature [36.5 °C (± 0.3)], heart rate [146.5/min (± 14)], and oxygen saturation [94% (± 4)]. No severe or moderate side-effects were noted; one baby developed mild dermatitis under the device that was transient and self-limiting, yielding an incidence proportion of 20% and incidence rate of 2.6/100 person-days. None of the mothers reported any discomfort with the use of the device. Temperatures detected from 81 paired readings revealed that those from the wearable sensor were 0.2 °C lower than those detected by clinical thermometers [36.4 (± 0.7) vs 36.6 (± 0.3); < 0.001]. There was also iterative feedback that was useful for hardware and software design specifications of the wearable sensor, the gateway device, and the analytics platform. Lastly, lessons were learnt with regard to the logistics of research team interactions with healthcare professionals and study participants during the hospitalization and post-discharge home phases of the study. Conclusions: The pilot study has shown that it is feasible and acceptable to track KMC adherence as well as maternal and newborn temperatures in a potentially safe manner on a real-time mode for several days’ duration during hospitalization and home phases. The pilot has also helped inform modifications in clinical monitoring, technological modifications, and logistics planning in preparation for the definitive clinical trial.}, keywords = {Remote Neonatal Monitoring and Intervention}, pubstate = {published}, tppubtype = {article} } Background: Remote biomonitoring of vital parameters in hospitals and homes has the potential to improve coverage and quality of maternal and neonatal health. Wearable sensors coupled with modern information and communication technology now offer an opportunity to monitor temperatures and kangaroo mother care (KMC) adherence in a continuous and real-time manner remotely for several days’ duration in hospital and home settings. Using an innovative remote biomonitoring device to measure both temperature and baby position, we undertook a techno-feasibility study in preparation for a clinical trial. Methods: We designed and developed a wearable sensor for tracking KMC adherence and neonatal temperature, using social innovation design principles. After screening mother-infant dyads using clinical and logistic eligibility criteria, we piloted this wearable sensor along with a gateway device and the commercial cellular network. The dyads were recruited during hospitalization and followed up in the hospital and home phases for several days. Simple descriptive statistical analysis was undertaken. Results: Recruitment rate was 50% (6/12), and consenting rate was 83% (5/6) during a 2-month period. These five neonates contributed a total of 39 study days (15 hospital days and 24 home days). Their mean [± standard deviation (S.D.)] birth weight was 1490 (± 244) g. The mean (± S.D.) of the vital signs for the five babies was temperature [36.5 °C (± 0.3)], heart rate [146.5/min (± 14)], and oxygen saturation [94% (± 4)]. No severe or moderate side-effects were noted; one baby developed mild dermatitis under the device that was transient and self-limiting, yielding an incidence proportion of 20% and incidence rate of 2.6/100 person-days. None of the mothers reported any discomfort with the use of the device. Temperatures detected from 81 paired readings revealed that those from the wearable sensor were 0.2 °C lower than those detected by clinical thermometers [36.4 (± 0.7) vs 36.6 (± 0.3); < 0.001]. There was also iterative feedback that was useful for hardware and software design specifications of the wearable sensor, the gateway device, and the analytics platform. Lastly, lessons were learnt with regard to the logistics of research team interactions with healthcare professionals and study participants during the hospitalization and post-discharge home phases of the study. Conclusions: The pilot study has shown that it is feasible and acceptable to track KMC adherence as well as maternal and newborn temperatures in a potentially safe manner on a real-time mode for several days’ duration during hospitalization and home phases. The pilot has also helped inform modifications in clinical monitoring, technological modifications, and logistics planning in preparation for the definitive clinical trial. |
| 25. | Rathod, Nihesh; Subramanian, Renu; Sundaresan, Rajesh Data-driven and GIS-based coverage estimation in a heterogeneous propagation environment Conference Forthcoming Proceedings of the 2018 IEEE Global Communications Conference: Selected Areas in Communications: Internet of Things, 9.-13.12.18, Abu Dhabi (UAE), Forthcoming. BibTeX | Tags: Electrical Communications Engineering @conference{Rathod2018, title = {Data-driven and GIS-based coverage estimation in a heterogeneous propagation environment}, author = {Nihesh Rathod and Renu Subramanian and Rajesh Sundaresan}, year = {2018}, date = {2018-12-13}, booktitle = {Proceedings of the 2018 IEEE Global Communications Conference: Selected Areas in Communications: Internet of Things, 9.-13.12.18, Abu Dhabi (UAE)}, keywords = {Electrical Communications Engineering}, pubstate = {forthcoming}, tppubtype = {conference} } |
| 26. | Chakravarthy, Shanthanu; Balakuntala, Mythra V S; Rao, Ashwin M; Thakur, Ravi Kumar; Ananthasuresh, G K Development of an integrated haptic system for simulating upper gastrointestinal endoscopy Journal Article Mechatronics, 56 (12), pp. 115-131, 2018. Abstract | BibTeX | Tags: Cyber Surgery and Remote Patient Care | Links: @article{Chakravarthy2018, title = {Development of an integrated haptic system for simulating upper gastrointestinal endoscopy}, author = {Shanthanu Chakravarthy and Mythra V. S. Balakuntala and Ashwin M. Rao and Ravi Kumar Thakur and G. K. Ananthasuresh}, url = {http://www.rbccps.org/wp-content/uploads/2018/12/1-s2.0-S0957415818301636-main.pdf}, doi = {10.1016/j.mechatronics.2018.10.006}, year = {2018}, date = {2018-11-12}, journal = {Mechatronics}, volume = {56}, number = {12}, pages = {115-131}, abstract = {Virtual reality together with haptics offers immersive and flexible platforms for training doctors in medical procedures. In this paper, we present mechanical design, control, integration, and user-studies of a virtual reality-based haptic simulator for Upper Gastrointestinal (GI) endoscopy. The design overcomes some of the limitations of the existing systems. First, there is an extra degree of freedom for simulating junctions controlled by sphincter muscles in addition to translational and rotational degrees of freedom along and about the axis of the endoscope-tube. Second, the force-feedback is continuous over a longer range in all three degrees of freedom. Third, multiple insertions and removals of the tube are made possible with a magnetically actuated snap-fit mechanism. A Dynamics-based feed-forward control algorithm is developed and characterized for fidelity and transparency. The system provides continuous force up to 11 N in the axial direction and continuous torque up to 255 mN.m about the axial direction. The haptic device is integrated with a physics-based Virtual Reality (VR) interface. Furthermore, an immersion study was conducted using the integrated system with a cohort of novice and experienced clinicians. The haptic response and virtual model were rated high and improvements were suggested for graphical visualization and physical arrangement.}, keywords = {Cyber Surgery and Remote Patient Care}, pubstate = {published}, tppubtype = {article} } Virtual reality together with haptics offers immersive and flexible platforms for training doctors in medical procedures. In this paper, we present mechanical design, control, integration, and user-studies of a virtual reality-based haptic simulator for Upper Gastrointestinal (GI) endoscopy. The design overcomes some of the limitations of the existing systems. First, there is an extra degree of freedom for simulating junctions controlled by sphincter muscles in addition to translational and rotational degrees of freedom along and about the axis of the endoscope-tube. Second, the force-feedback is continuous over a longer range in all three degrees of freedom. Third, multiple insertions and removals of the tube are made possible with a magnetically actuated snap-fit mechanism. A Dynamics-based feed-forward control algorithm is developed and characterized for fidelity and transparency. The system provides continuous force up to 11 N in the axial direction and continuous torque up to 255 mN.m about the axial direction. The haptic device is integrated with a physics-based Virtual Reality (VR) interface. Furthermore, an immersion study was conducted using the integrated system with a cohort of novice and experienced clinicians. The haptic response and virtual model were rated high and improvements were suggested for graphical visualization and physical arrangement. |
| 27. | Karanjkar, Neha; Joglekar, Ashish; Mohanty, Sampad; Prabu, Venkatesh; Raghunathan, D; Sundaresan, Rajesh Digital twin for energy optimization in an SMT-PCB assembly line Conference Forthcoming Proceedings of the IEEE 2018 International Conference on Internet of Things and Intelligence Systems (IoTAIS), 01.-03.11.18, Bali (Indonesia), Forthcoming. Abstract | BibTeX | Tags: Industrial Internet of Things @conference{Karanjkar2018, title = {Digital twin for energy optimization in an SMT-PCB assembly line }, author = {Neha Karanjkar and Ashish Joglekar and Sampad Mohanty and Venkatesh Prabu and D. Raghunathan and Rajesh Sundaresan}, year = {2018}, date = {2018-11-03}, booktitle = {Proceedings of the IEEE 2018 International Conference on Internet of Things and Intelligence Systems (IoTAIS), 01.-03.11.18, Bali (Indonesia)}, abstract = {This paper presents a case study for the use of an IoT-driven digital twin for energy optimization in an automated Surface Mount Technology (SMT) PCB assembly line containing legacy machines. The line was instrumented with multiple sensors for measuring machine-wise activity and energy consumption. A software platform for data aggregation and a discrete-event digital twin of the line were built entirely using open-source tools. Based on the insights gained from data collected over several days, we propose a buffering-based solution for improving the energy efficiency of the line, and evaluate its impact using simulations of the digital twin. The results show that a 2.7x reduction in the energy consumption is possible via buffer insertion without significantly affecting line throughput.}, keywords = {Industrial Internet of Things}, pubstate = {forthcoming}, tppubtype = {conference} } This paper presents a case study for the use of an IoT-driven digital twin for energy optimization in an automated Surface Mount Technology (SMT) PCB assembly line containing legacy machines. The line was instrumented with multiple sensors for measuring machine-wise activity and energy consumption. A software platform for data aggregation and a discrete-event digital twin of the line were built entirely using open-source tools. Based on the insights gained from data collected over several days, we propose a buffering-based solution for improving the energy efficiency of the line, and evaluate its impact using simulations of the digital twin. The results show that a 2.7x reduction in the energy consumption is possible via buffer insertion without significantly affecting line throughput. |
| 28. | Kolathaya, Shishir; Guffey, William; Sinnet, Ryan W; Ames, Aaron D Direct Collocation for dynamic behaviors with nonprehensile contacts: Application to flipping burgers Journal Article IEEE Robotics and Automation Letters, 3 (4), pp. 3677-3684, 2018. Abstract | BibTeX | Tags: Autonomous Systems | Links: @article{Kolathaya2018b, title = {Direct Collocation for dynamic behaviors with nonprehensile contacts: Application to flipping burgers}, author = {Shishir Kolathaya and William Guffey and Ryan W. Sinnet and Aaron D. Ames}, url = {http://www.rbccps.org/wp-content/uploads/2018/12/08410040.pdf}, doi = {10.1109/LRA.2018.2854910}, year = {2018}, date = {2018-10-31}, journal = {IEEE Robotics and Automation Letters}, volume = {3}, number = {4}, pages = {3677-3684}, abstract = {To realize robotic systems in real-world settings, e.g., in restaurants, it will be necessary to achieve dynamic manipulation of nontrivial objects. In this context, this letter discusses methodologies used to realize trajectories in a robotic arm platform, specifically, applied to flipping burgers as an example of nonprehensile object manipulation. Flipping of burgers involves a series of tasks-going to the burger location, scooping, picking up, and flipping. Since the goal is to obtain these trajectories in a reasonably fast manner, we employ direct collocation based multisegmented trajectory optimization. We will first describe the problem setup, and then describe the constraints, decision variables employed, and then, to conclude, we will demonstrate these behaviors in a 6-DOF robot experimentally.}, keywords = {Autonomous Systems}, pubstate = {published}, tppubtype = {article} } To realize robotic systems in real-world settings, e.g., in restaurants, it will be necessary to achieve dynamic manipulation of nontrivial objects. In this context, this letter discusses methodologies used to realize trajectories in a robotic arm platform, specifically, applied to flipping burgers as an example of nonprehensile object manipulation. Flipping of burgers involves a series of tasks-going to the burger location, scooping, picking up, and flipping. Since the goal is to obtain these trajectories in a reasonably fast manner, we employ direct collocation based multisegmented trajectory optimization. We will first describe the problem setup, and then describe the constraints, decision variables employed, and then, to conclude, we will demonstrate these behaviors in a 6-DOF robot experimentally. |
| 29. | Ghosh, Rajrup; Simmhan, Yogesh Distributed scheduling of event analytics across edge and cloud Journal Article ACM Transactions on Cyber-Physical Systems, 2 (4), pp. 24:1-28, 2018. Abstract | BibTeX | Tags: Smart City, Student Research Grant | Links: @article{Ghosh2018, title = {Distributed scheduling of event analytics across edge and cloud}, author = {Rajrup Ghosh and Yogesh Simmhan}, url = {http://www.rbccps.org/wp-content/uploads/2018/12/a24-ghosh.pdf}, doi = {10.1145/3140256}, year = {2018}, date = {2018-10-31}, journal = {ACM Transactions on Cyber-Physical Systems}, volume = {2}, number = {4}, pages = {24:1-28}, abstract = {Internet of Things (IoT) domains generate large volumes of high-velocity event streams from sensors, which need to be analyzed with low latency to drive decisions. Complex Event Processing (CEP) is a Big Data technique to enable such analytics and is traditionally performed on Cloud Virtual Machines (VM). Leveraging captive IoT edge resources in combination with Cloud VMs can offer better performance, flexibility, and monetary costs for CEP. Here, we formulate an optimization problem for energy-aware placement of CEP queries, composed as an analytics dataflow, across a collection of edge and Cloud resources, with the goal of minimizing the end-to-end latency for the dataflow. We propose a Genetic Algorithm (GA) meta-heuristic to solve this problem and compare it against a brute-force optimal algorithm (BF). We perform detailed real-world benchmarks on the compute, network, and energy capacity of edge and Cloud resources. These results are used to define a realistic and comprehensive simulation study that validates the BF and GA solutions for 45 diverse CEP dataflows, LAN and WAN setup, and different edge resource availability. We compare the GA and BF solutions against random and Cloud-only baselines for different configurations for a total of 1,764 simulation runs. Our study shows that GA is within 97% of the optimal BF solution that takes hours, maps dataflows with 4--50 queries in 1--26s, and only fails to offer a feasible solution ≤20% of the time.}, keywords = {Smart City, Student Research Grant}, pubstate = {published}, tppubtype = {article} } Internet of Things (IoT) domains generate large volumes of high-velocity event streams from sensors, which need to be analyzed with low latency to drive decisions. Complex Event Processing (CEP) is a Big Data technique to enable such analytics and is traditionally performed on Cloud Virtual Machines (VM). Leveraging captive IoT edge resources in combination with Cloud VMs can offer better performance, flexibility, and monetary costs for CEP. Here, we formulate an optimization problem for energy-aware placement of CEP queries, composed as an analytics dataflow, across a collection of edge and Cloud resources, with the goal of minimizing the end-to-end latency for the dataflow. We propose a Genetic Algorithm (GA) meta-heuristic to solve this problem and compare it against a brute-force optimal algorithm (BF). We perform detailed real-world benchmarks on the compute, network, and energy capacity of edge and Cloud resources. These results are used to define a realistic and comprehensive simulation study that validates the BF and GA solutions for 45 diverse CEP dataflows, LAN and WAN setup, and different edge resource availability. We compare the GA and BF solutions against random and Cloud-only baselines for different configurations for a total of 1,764 simulation runs. Our study shows that GA is within 97% of the optimal BF solution that takes hours, maps dataflows with 4--50 queries in 1--26s, and only fails to offer a feasible solution ≤20% of the time. |
| 30. | Sawant, Omkar; Bhowmick, Anirban; Sreenivas, Thippur V Enhanced directional sensitivity using acoustic dish reflector Conference Forthcoming Proceedings of the International Conference on Signal Processing and Communications (SPCOM 2018), 16.-19.07.18, Bangalore (India), Forthcoming. Abstract | BibTeX | Tags: Sensing and Actuation Systems | Links: @conference{Sawant2018, title = {Enhanced directional sensitivity using acoustic dish reflector}, author = {Omkar Sawant and Anirban Bhowmick and Thippur V. Sreenivas}, url = {http://www.rbccps.org/wp-content/uploads/2018/05/PID5361497.pdf}, year = {2018}, date = {2018-07-19}, booktitle = {Proceedings of the International Conference on Signal Processing and Communications (SPCOM 2018), 16.-19.07.18, Bangalore (India)}, abstract = {An acoustic reflector is a passive device which is used with microphones to reflect and focus sound waves from a longer distance. They are effective for long-range sound recording without intrusion, such as to record wildlife sounds. In this paper, our objective is to investigate the feasibility of using a dish reflector microphone for indoor activity monitoring of large premises. Acoustic gain and frequency response of the microphone with different parabolic, near parabolic and non- parabolic reflectors are compared with that of the same micro- phone without the reflector. It is observed that the use of dish reflector does significantly enhance the directivity and sensitivity of sound recording. Keeping to a moderate size reflector, among various shapes and materials, the best reflector has given a 14 dB gain improvement over microphone without reflector at 0 degree azimuth. We also found that among steel and plastic dish reflector of approximately same size and shape, steel dish reflector does give a higher performance as expected. The increased directivity of the dish reflector is giving a significant improvement in indoor monitoring and also for sound source tracking.}, keywords = {Sensing and Actuation Systems}, pubstate = {forthcoming}, tppubtype = {conference} } An acoustic reflector is a passive device which is used with microphones to reflect and focus sound waves from a longer distance. They are effective for long-range sound recording without intrusion, such as to record wildlife sounds. In this paper, our objective is to investigate the feasibility of using a dish reflector microphone for indoor activity monitoring of large premises. Acoustic gain and frequency response of the microphone with different parabolic, near parabolic and non- parabolic reflectors are compared with that of the same micro- phone without the reflector. It is observed that the use of dish reflector does significantly enhance the directivity and sensitivity of sound recording. Keeping to a moderate size reflector, among various shapes and materials, the best reflector has given a 14 dB gain improvement over microphone without reflector at 0 degree azimuth. We also found that among steel and plastic dish reflector of approximately same size and shape, steel dish reflector does give a higher performance as expected. The increased directivity of the dish reflector is giving a significant improvement in indoor monitoring and also for sound source tracking. |
| 31. | Kumar, Saurabh; Amrutur, Bharadwaj; Asokan, Sundarrajan Evaluation of Fiber Bragg Grating sensor interrogation using InGaAs linear detector arrays and Gaussian approximation on embedded hardware Journal Article Review of Scientific Instruments, 89 (2), 2018. Abstract | BibTeX | Tags: Fiber Bragg Grating Sensors for Distributed Bio-Chemical Sensing | Links: @article{Kumar2018b, title = {Evaluation of Fiber Bragg Grating sensor interrogation using InGaAs linear detector arrays and Gaussian approximation on embedded hardware}, author = {Saurabh Kumar and Bharadwaj Amrutur and Sundarrajan Asokan}, url = {http://www.rbccps.org/wp-content/uploads/2018/06/1.5022548.pdf}, doi = {10.1063/1.5022548}, year = {2018}, date = {2018-02-28}, journal = {Review of Scientific Instruments}, volume = {89}, number = {2}, abstract = {Fiber Bragg Grating (FBG) sensors have become popular for applications related to structural health monitoring, biomedical engineering, and robotics. However, for successful large scale adoption, FBG interrogation systems are as important as sensor characteristics. Apart from accuracy, the required number of FBG sensors per fiber and the distance between the device in which the sensors are used and the interrogation system also influence the selection of the interrogation technique. For several measurement devices developed for applications in biomedical engineering and robotics, only a few sensors per fiber are required and the device is close to the interrogation system. For these applications, interrogation systems based on InGaAs linear detector arrays provide a good choice. However, their resolution is dependent on the algorithms used for curve fitting. In this work, a detailed analysis of the choice of algorithm using the Gaussian approximation for the FBG spectrum and the number of pixels used for curve fitting on the errors is provided. The points where the maximum errors occur have been identified. All comparisons for wavelength shift detection have been made against another interrogation system based on the tunable swept laser. It has been shown that maximum errors occur when the wavelength shift is such that one new pixel is included for curve fitting. It has also been shown that an algorithm with lower computation cost compared to the more popular methods using iterative non-linear least squares estimation can be used without leading to the loss of accuracy. The algorithm has been implemented on embedded hardware, and a speed-up of approximately six times has been observed.}, keywords = {Fiber Bragg Grating Sensors for Distributed Bio-Chemical Sensing}, pubstate = {published}, tppubtype = {article} } Fiber Bragg Grating (FBG) sensors have become popular for applications related to structural health monitoring, biomedical engineering, and robotics. However, for successful large scale adoption, FBG interrogation systems are as important as sensor characteristics. Apart from accuracy, the required number of FBG sensors per fiber and the distance between the device in which the sensors are used and the interrogation system also influence the selection of the interrogation technique. For several measurement devices developed for applications in biomedical engineering and robotics, only a few sensors per fiber are required and the device is close to the interrogation system. For these applications, interrogation systems based on InGaAs linear detector arrays provide a good choice. However, their resolution is dependent on the algorithms used for curve fitting. In this work, a detailed analysis of the choice of algorithm using the Gaussian approximation for the FBG spectrum and the number of pixels used for curve fitting on the errors is provided. The points where the maximum errors occur have been identified. All comparisons for wavelength shift detection have been made against another interrogation system based on the tunable swept laser. It has been shown that maximum errors occur when the wavelength shift is such that one new pixel is included for curve fitting. It has also been shown that an algorithm with lower computation cost compared to the more popular methods using iterative non-linear least squares estimation can be used without leading to the loss of accuracy. The algorithm has been implemented on embedded hardware, and a speed-up of approximately six times has been observed. |
| 32. | Kumar, Navneet; Arakeri, Jaywant H Evaporation from confined porous media due to controlled IR heating from above Journal Article Transport in Porous Media, 125 , pp. 311-340, 2018. Abstract | BibTeX | Tags: Student Research Grant | Links: @article{Kumar2018e, title = {Evaporation from confined porous media due to controlled IR heating from above}, author = {Navneet Kumar and Jaywant H. Arakeri}, url = {http://www.rbccps.org/wp-content/uploads/2018/12/Kumar-Arakeri2018_Article_EvaporationFromConfinedPorousM.pdf}, doi = {10.1007/s11242-018-1120-4}, year = {2018}, date = {2018-11-30}, journal = {Transport in Porous Media}, volume = {125}, pages = {311-340}, abstract = {We report an experimental study of evaporation due to controlled infrared (IR) heating from above from an initially saturated confined porous medium consisting of nearly ‘mono-disperse’ particles which has been rarely used earlier. We have used three diagnostic tools simultaneously, evaporation rate measurements using a precision weighing balance, surface temperature measurements using IR imaging, and fluorescein dye mixed with water to visualize the drying front and the evaporation sites. IR images show that the first stage, so-called constant rate period (CRP), was maintained due to films of water reaching the top surface from the saturated region below. Gradually reducing evaporation rate in stage 1 is shown to be related to ‘shrinking evaporating patches’ on the top surface, clearly revealed as lower-temperature regions in the IR images. End of CRP coincides with disappearance of the low-temperature patches. We give end of CRP in terms of the average depth (Lcap) of the liquid level from the top surface at that time. Lcap and duration of CRP are strong functions of the porous medium bead size, transition to stage 2 happening earlier for coarser spheres. The obtained Lcap values deviated from the predictions of Lehmann et al. (Phys Rev E 77(5):056309, 2008) which we show is due to a small range of pore sizes in the current experiments. For both water and highly volatile n-pentane, we show that Lcap normalized by a length scale derived from gravity-surface tension force balance goes like Bo^0.20, for Bo varying from 2.0E − 04 to 1.0E − 01; Bo is the Bond number. Fluorescein dye imaging shows a different view of the evaporation stages. During CRP, highly concentrated deposits of the fluorescein dye particles, orange in colour, are seen in the top few bead layers. These orange deposits represent the sites on the beads surfaces where the evaporation has taken place. Even with external heating, evaporation from such a porous medium is limited to a finite depth from the evaporating end, similar to the observation by Lehmann et al. (2008) for isothermal evaporation in Hele-Shaw cell. }, keywords = {Student Research Grant}, pubstate = {published}, tppubtype = {article} } We report an experimental study of evaporation due to controlled infrared (IR) heating from above from an initially saturated confined porous medium consisting of nearly ‘mono-disperse’ particles which has been rarely used earlier. We have used three diagnostic tools simultaneously, evaporation rate measurements using a precision weighing balance, surface temperature measurements using IR imaging, and fluorescein dye mixed with water to visualize the drying front and the evaporation sites. IR images show that the first stage, so-called constant rate period (CRP), was maintained due to films of water reaching the top surface from the saturated region below. Gradually reducing evaporation rate in stage 1 is shown to be related to ‘shrinking evaporating patches’ on the top surface, clearly revealed as lower-temperature regions in the IR images. End of CRP coincides with disappearance of the low-temperature patches. We give end of CRP in terms of the average depth (Lcap) of the liquid level from the top surface at that time. Lcap and duration of CRP are strong functions of the porous medium bead size, transition to stage 2 happening earlier for coarser spheres. The obtained Lcap values deviated from the predictions of Lehmann et al. (Phys Rev E 77(5):056309, 2008) which we show is due to a small range of pore sizes in the current experiments. For both water and highly volatile n-pentane, we show that Lcap normalized by a length scale derived from gravity-surface tension force balance goes like Bo^0.20, for Bo varying from 2.0E − 04 to 1.0E − 01; Bo is the Bond number. Fluorescein dye imaging shows a different view of the evaporation stages. During CRP, highly concentrated deposits of the fluorescein dye particles, orange in colour, are seen in the top few bead layers. These orange deposits represent the sites on the beads surfaces where the evaporation has taken place. Even with external heating, evaporation from such a porous medium is limited to a finite depth from the evaporating end, similar to the observation by Lehmann et al. (2008) for isothermal evaporation in Hele-Shaw cell. |
| 33. | Kumar, Navneet; Arakeri, Jaywant H Evaporation from layered porous medium in the presence of infrared heating Journal Article Water Resources Research, 54 (10), pp. 7670-7687, 2018. Abstract | BibTeX | Tags: Student Research Grant | Links: @article{Kumar2018f, title = {Evaporation from layered porous medium in the presence of infrared heating}, author = {Navneet Kumar and Jaywant H. Arakeri}, url = {http://www.rbccps.org/wp-content/uploads/2018/12/Kumar_et_al-2018-Water_Resources_Research.pdf}, doi = {10.1029/2017WR021954}, year = {2018}, date = {2018-10-31}, journal = {Water Resources Research}, volume = {54}, number = {10}, pages = {7670-7687}, abstract = {We report an experimental study of evaporation of two configurations of layered porous media that are heated from above by infrared (IR) radiation having ~1,000 W/m^2 intensity. We used nearly monodisperse glass beads in each of the layers. The two configurations are (1) coarse and fine beads, stacked side by side and (2) fine beads over coarse beads (FoC). The IR heater mimics the natural evaporation process in soils, and the aim is to study, using three diagnostic tools, how the layering affects the evaporation process, and compare it with the homogeneous porous medium case. For each experiment we use three diagnostics simultaneously, evaporation rate measurement using a precision balance, surface temperature imaging using an IR camera, and visualization of the evaporation process with fluorescein dye. The constant (evaporation) rate period (CRP) regime, found in homogeneous porous media, is drastically changed for the two layered configurations. We show new results for side‐by‐side configuration. In the FoC configuration we show that the near‐surface water content in the finer particles does not change in CRP and a true constant evaporation rate is possible. The average water depth at end of CRP in the porous medium, for a wide range of diameter ratios for the FoC configuration are compared with the predictions from theoretical relations proposed by Shokri et al. (2010, https://doi.org/10.1029/2009JB006743) and Assouline et al. (2014, https://doi.org/10.1002/2013WR014489). Using a simple surface energy budget, we show that knowing the surface temperature, the evaporation rate can be estimated with reasonable accuracy (±5%) during drying of a porous medium. }, keywords = {Student Research Grant}, pubstate = {published}, tppubtype = {article} } We report an experimental study of evaporation of two configurations of layered porous media that are heated from above by infrared (IR) radiation having ~1,000 W/m^2 intensity. We used nearly monodisperse glass beads in each of the layers. The two configurations are (1) coarse and fine beads, stacked side by side and (2) fine beads over coarse beads (FoC). The IR heater mimics the natural evaporation process in soils, and the aim is to study, using three diagnostic tools, how the layering affects the evaporation process, and compare it with the homogeneous porous medium case. For each experiment we use three diagnostics simultaneously, evaporation rate measurement using a precision balance, surface temperature imaging using an IR camera, and visualization of the evaporation process with fluorescein dye. The constant (evaporation) rate period (CRP) regime, found in homogeneous porous media, is drastically changed for the two layered configurations. We show new results for side‐by‐side configuration. In the FoC configuration we show that the near‐surface water content in the finer particles does not change in CRP and a true constant evaporation rate is possible. The average water depth at end of CRP in the porous medium, for a wide range of diameter ratios for the FoC configuration are compared with the predictions from theoretical relations proposed by Shokri et al. (2010, https://doi.org/10.1029/2009JB006743) and Assouline et al. (2014, https://doi.org/10.1002/2013WR014489). Using a simple surface energy budget, we show that knowing the surface temperature, the evaporation rate can be estimated with reasonable accuracy (±5%) during drying of a porous medium. |
| 34. | Kumar, Navneet; Arakeri, Jaywant H Experimental investigation of effect of orientation and surface roughness on drying of porous media consisting of rods Journal Article International Journal of Multiphase Flow, 109 , pp. 114-122, 2018. Abstract | BibTeX | Tags: Student Research Grant | Links: @article{Kumar2018c, title = {Experimental investigation of effect of orientation and surface roughness on drying of porous media consisting of rods}, author = {Navneet Kumar and Jaywant H. Arakeri}, url = {http://www.rbccps.org/wp-content/uploads/2018/12/1-s2.0-S030193221731011X-main.pdf}, doi = {10.1016/j.ijmultiphaseflow.2018.07.009}, year = {2018}, date = {2018-12-03}, journal = {International Journal of Multiphase Flow}, volume = {109}, pages = {114-122}, abstract = {Studies of drying from a conventional porous medium (CPM), consisting of spheres, have shown the existence of three periods. In the first period drying rate is high and essentially depends on the atmospheric demand while in the last stage mass transfer happens from within the porous medium and is solely governed by the internal properties. In a previous study (Kumar and Arakeri) it was shown, using a cluster of closely packed smooth rods stacked vertically, that stage 1 was sustained till nearly the whole liquid gets evaporated. Near-zero radii contacts, between the rods, offering infinite height rise was shown to be the reason behind such high sustained evaporation rates and elongated duration of stage 1. Here we show that the orientation of the rods dramatically changes the evaporation process from this vertically oriented rod-based porous medium (VRBPM). Unlike the vertical case, in the horizontal case (HRBPM) smooth rods do not support stage 1. In this case transition to stage 2 was due to the liquid-vapour meniscus receding continuously in the network from the start of the experiment. Rough rods pinned the liquid along its rough surfaces and stage 1 is sustained although its duration is much smaller compared to the vertical case. Maintained hydraulic connections against gravity along the roughness of the rods thus provides a better insight towards understanding stage 1 in a conventional porous medium consisting of complicated pore geometry and their connectivity. In all the experiments, infra-red heating at about 1000 W/m2 causes evaporation from an initially saturated RBPM kept in an acrylic box.}, keywords = {Student Research Grant}, pubstate = {published}, tppubtype = {article} } Studies of drying from a conventional porous medium (CPM), consisting of spheres, have shown the existence of three periods. In the first period drying rate is high and essentially depends on the atmospheric demand while in the last stage mass transfer happens from within the porous medium and is solely governed by the internal properties. In a previous study (Kumar and Arakeri) it was shown, using a cluster of closely packed smooth rods stacked vertically, that stage 1 was sustained till nearly the whole liquid gets evaporated. Near-zero radii contacts, between the rods, offering infinite height rise was shown to be the reason behind such high sustained evaporation rates and elongated duration of stage 1. Here we show that the orientation of the rods dramatically changes the evaporation process from this vertically oriented rod-based porous medium (VRBPM). Unlike the vertical case, in the horizontal case (HRBPM) smooth rods do not support stage 1. In this case transition to stage 2 was due to the liquid-vapour meniscus receding continuously in the network from the start of the experiment. Rough rods pinned the liquid along its rough surfaces and stage 1 is sustained although its duration is much smaller compared to the vertical case. Maintained hydraulic connections against gravity along the roughness of the rods thus provides a better insight towards understanding stage 1 in a conventional porous medium consisting of complicated pore geometry and their connectivity. In all the experiments, infra-red heating at about 1000 W/m2 causes evaporation from an initially saturated RBPM kept in an acrylic box. |
| 35. | Amrutur, Bharadwaj; Darbari, Hemant Final report on the project "Study of India appropriate technology (IoT) solutions for Smart Cities" Technical Report 2018. Abstract | BibTeX | Tags: Smart City | Links: @techreport{Amrutur2018, title = {Final report on the project "Study of India appropriate technology (IoT) solutions for Smart Cities"}, author = {Bharadwaj Amrutur and Hemant Darbari}, url = {http://www.rbccps.org/wp-content/uploads/2018/10/IISc_IoT4SmartCities_Consolidated_Report.pdf}, year = {2018}, date = {2018-04-30}, abstract = {The main objectives of our project are: (1) Recommendation and guidelines for Smart City RFPs related to IoT specific technologies, driven by India specific use case analysis and emerging technology adoption methodology, and (2) India appropriate reference architecture for IoT enabled Smart cities through a collaborative platform of domain experts from industry, academia, government, start-ups, professional bodies and user agencies. We conducted two workshops with City administrators: One in Chandigarh and another in Electronics City, to understand the city’s requirements. A series of telecons/webcons were held with technical presentations from a diverse set of domain experts from industry, academia, government, startups, etc. Further deliberations and discussions were done to synthesize the view points in this report.}, keywords = {Smart City}, pubstate = {published}, tppubtype = {techreport} } The main objectives of our project are: (1) Recommendation and guidelines for Smart City RFPs related to IoT specific technologies, driven by India specific use case analysis and emerging technology adoption methodology, and (2) India appropriate reference architecture for IoT enabled Smart cities through a collaborative platform of domain experts from industry, academia, government, start-ups, professional bodies and user agencies. We conducted two workshops with City administrators: One in Chandigarh and another in Electronics City, to understand the city’s requirements. A series of telecons/webcons were held with technical presentations from a diverse set of domain experts from industry, academia, government, startups, etc. Further deliberations and discussions were done to synthesize the view points in this report. |
| 36. | Prakash, Praneet; Pahal, Suman; Varma, Manoj Fluorescence recovery after photobleaching in ultrathin polymer films Journal Article Macromolecular Chemistry and Physics, 219 (7), 2018. Abstract | BibTeX | Tags: Sensing and Actuation Systems | Links: @article{Prakash2018, title = {Fluorescence recovery after photobleaching in ultrathin polymer films}, author = {Praneet Prakash and Suman Pahal and Manoj Varma}, url = {http://www.rbccps.org/wp-content/uploads/2018/12/Prakash_et_al-2018-Macromolecular_Chemistry_and_Physics.pdf}, doi = {10.1002/macp.201700543}, year = {2018}, date = {2018-02-05}, journal = {Macromolecular Chemistry and Physics}, volume = {219}, number = {7}, abstract = {Fluorescence recovery after photobleaching (FRAP) is a widely used technique to study the transport of molecules in biological systems. Recently, FRAP has been used to study molecular transport in polyelectrolyte multilayers (PEMs). Through numerical simulations verified by experiments, it is shown that the FRAP behavior of PEM films in an aqueous medium differs significantly from that in previously explored systems such as single cells. This is because fluorescence recovery can take place through the aqueous medium surrounding the PEM film. The simulations show the critical role of the time scale of the different processes, namely, diffusion through PEM, diffusion through surrounding medium, and the unbinding rate of fluorophore‐labeled species in the interpretation of FRAP data. An important conclusion from the numerical and experimental study is that, for ultrathin PEM films with ≈100 nm thicknesses, recovery is dominated through the solution medium and hence, classical FRAP analysis is not sufficient to probe diffusion in PEM. The numerical study reveals several aspects of the FRAP phenomena in thin polymer films that are critical for the proper interpretation of experimental data.}, keywords = {Sensing and Actuation Systems}, pubstate = {published}, tppubtype = {article} } Fluorescence recovery after photobleaching (FRAP) is a widely used technique to study the transport of molecules in biological systems. Recently, FRAP has been used to study molecular transport in polyelectrolyte multilayers (PEMs). Through numerical simulations verified by experiments, it is shown that the FRAP behavior of PEM films in an aqueous medium differs significantly from that in previously explored systems such as single cells. This is because fluorescence recovery can take place through the aqueous medium surrounding the PEM film. The simulations show the critical role of the time scale of the different processes, namely, diffusion through PEM, diffusion through surrounding medium, and the unbinding rate of fluorophore‐labeled species in the interpretation of FRAP data. An important conclusion from the numerical and experimental study is that, for ultrathin PEM films with ≈100 nm thicknesses, recovery is dominated through the solution medium and hence, classical FRAP analysis is not sufficient to probe diffusion in PEM. The numerical study reveals several aspects of the FRAP phenomena in thin polymer films that are critical for the proper interpretation of experimental data. |
| 37. | Babu, Arun; Thomas, Jithin Jose Freestyle, a randomized version of ChaCha for resisting offline brute-force and dictionary attacks Journal Article arXiv: Computer Science, 2018. Abstract | BibTeX | Tags: Smart City @article{Babu2018, title = {Freestyle, a randomized version of ChaCha for resisting offline brute-force and dictionary attacks}, author = {Arun Babu and Jithin Jose Thomas}, year = {2018}, date = {2018-02-09}, journal = {arXiv: Computer Science}, abstract = {This paper introduces Freestyle, a randomized and variable round version of the ChaCha cipher. Freestyle uses the concept of hash based halting condition where a decryption attempt with an incorrect key is likely to take longer time to halt. This makes Freestyle resistant to key-guessing attacks i.e. brute-force and dictionary based attacks. Freestyle demonstrates a novel approach for ciphertext randomization by using random number of rounds for each block, where the exact number of rounds are unknown to the receiver in advance. Freestyle provides the possibility of generating 2^128 different ciphertexts for a given key, nonce, and message; thus resisting key and nonce reuse attacks. Due to its inherent random behavior, Freestyle makes cryptanalysis through known-plaintext, chosen-plaintext, and chosen-ciphertext attacks difficult in practice. On the other hand, Freestyle has costlier cipher initialization process, typically generates 3.125% larger ciphertext, and was found to be 1.6 to 3.2 times slower than ChaCha20. Freestyle is suitable for applications that favor ciphertext randomization and resistance to key-guessing and key reuse attacks over performance and ciphertext size. Freestyle is ideal for applications where ciphertext can be assumed to be in full control of an adversary, and an offline key-guessing attack can be carried out. }, keywords = {Smart City}, pubstate = {published}, tppubtype = {article} } This paper introduces Freestyle, a randomized and variable round version of the ChaCha cipher. Freestyle uses the concept of hash based halting condition where a decryption attempt with an incorrect key is likely to take longer time to halt. This makes Freestyle resistant to key-guessing attacks i.e. brute-force and dictionary based attacks. Freestyle demonstrates a novel approach for ciphertext randomization by using random number of rounds for each block, where the exact number of rounds are unknown to the receiver in advance. Freestyle provides the possibility of generating 2^128 different ciphertexts for a given key, nonce, and message; thus resisting key and nonce reuse attacks. Due to its inherent random behavior, Freestyle makes cryptanalysis through known-plaintext, chosen-plaintext, and chosen-ciphertext attacks difficult in practice. On the other hand, Freestyle has costlier cipher initialization process, typically generates 3.125% larger ciphertext, and was found to be 1.6 to 3.2 times slower than ChaCha20. Freestyle is suitable for applications that favor ciphertext randomization and resistance to key-guessing and key reuse attacks over performance and ciphertext size. Freestyle is ideal for applications where ciphertext can be assumed to be in full control of an adversary, and an offline key-guessing attack can be carried out. |
| 38. | Zhou, Enlu; Bhatnagar, Shalabh Gradient-based adaptive stochastic search for simulation optimization over continuous space Journal Article INFORMS Journal on Computing, 30 (1), pp. 154-167, 2018. Abstract | BibTeX | Tags: Control and Optimisation | Links: @article{Zhou2018, title = {Gradient-based adaptive stochastic search for simulation optimization over continuous space}, author = {Enlu Zhou and Shalabh Bhatnagar}, url = {http://www.rbccps.org/wp-content/uploads/2018/08/ijoc.2017.0771.pdf}, doi = {10.1287/ijoc.2017.0771}, year = {2018}, date = {2018-01-23}, journal = {INFORMS Journal on Computing}, volume = {30}, number = {1}, pages = {154-167}, abstract = {We extend the idea of model-based algorithms for deterministic optimization to simulation optimization over continuous space. Model-based algorithms iteratively generate a population of candidate solutions from a sampling distribution and use the performance of the candidate solutions to update the sampling distribution. By viewing the original simulation optimization problem as another optimization problem over the parameter space of the sampling distribution, we propose to use a direct gradient search on the parameter space to update the sampling distribution. To improve the computational efficiency, we further develop a two-timescale updating scheme that updates the parameter on a slow timescale and estimates the quantities involved in the parameter updating on the fast timescale. We analyze the convergence properties of our algorithms through techniques from stochastic approximation, and demonstrate the good empirical performance by comparing with two state-of-the-art model-based simulation optimization methods.}, keywords = {Control and Optimisation}, pubstate = {published}, tppubtype = {article} } We extend the idea of model-based algorithms for deterministic optimization to simulation optimization over continuous space. Model-based algorithms iteratively generate a population of candidate solutions from a sampling distribution and use the performance of the candidate solutions to update the sampling distribution. By viewing the original simulation optimization problem as another optimization problem over the parameter space of the sampling distribution, we propose to use a direct gradient search on the parameter space to update the sampling distribution. To improve the computational efficiency, we further develop a two-timescale updating scheme that updates the parameter on a slow timescale and estimates the quantities involved in the parameter updating on the fast timescale. We analyze the convergence properties of our algorithms through techniques from stochastic approximation, and demonstrate the good empirical performance by comparing with two state-of-the-art model-based simulation optimization methods. |
| 39. | Somasundaran, Biju Venkadath; Soundararajan, Rajiv; Biswas, Soma Image denoising for image retrieval by cascading a deep quality assessment network Conference Proceedings of the 25th IEEE International Conference on Image Processing (ICIP), 07.-10.10.18, Athens (Greece), 2018. Abstract | BibTeX | Tags: Student Research Grant | Links: @conference{Somasundaran2018, title = {Image denoising for image retrieval by cascading a deep quality assessment network}, author = {Biju Venkadath Somasundaran and Rajiv Soundararajan and Soma Biswas}, url = {http://www.rbccps.org/wp-content/uploads/2018/12/08451132.pdf}, doi = {10.1109/ICIP.2018.8451132}, year = {2018}, date = {2018-09-06}, booktitle = {Proceedings of the 25th IEEE International Conference on Image Processing (ICIP), 07.-10.10.18, Athens (Greece)}, abstract = {Image denoising algorithms have evolved to optimize image quality as measured according to human visual perception. However, image denoising to maximize the success of computer vision algorithms operating on the denoised image has been much less investigated. We consider the problem of image denoising for Gaussian noise with respect to the specific application of image retrieval from a dataset. We define the notion of image quality as determined by the success of image retrieval and design a deep convolutional neural network (CNN) to predict this quality. This network is then cascaded with a deep CNN designed for image denoising, allowing for optimization of the denoising CNN to maximize retrieval performance. This framework allows us to couple denoising to the retrieval problem. We show through experiments on noisy images of the Oxford and Paris buildings datasets that such an approach yields improved mean average precision when compared to using denoising methods that are oblivious to the task of image retrieval.}, keywords = {Student Research Grant}, pubstate = {published}, tppubtype = {conference} } Image denoising algorithms have evolved to optimize image quality as measured according to human visual perception. However, image denoising to maximize the success of computer vision algorithms operating on the denoised image has been much less investigated. We consider the problem of image denoising for Gaussian noise with respect to the specific application of image retrieval from a dataset. We define the notion of image quality as determined by the success of image retrieval and design a deep convolutional neural network (CNN) to predict this quality. This network is then cascaded with a deep CNN designed for image denoising, allowing for optimization of the denoising CNN to maximize retrieval performance. This framework allows us to couple denoising to the retrieval problem. We show through experiments on noisy images of the Oxford and Paris buildings datasets that such an approach yields improved mean average precision when compared to using denoising methods that are oblivious to the task of image retrieval. |
| 40. | Kolathaya, Shishir; James, Aaron D Input-to-state safety with control barrier functions Journal Article IEEE Control Systems Letters, 3 (1), pp. 108-113, 2018. Abstract | BibTeX | Tags: Autonomous Systems | Links: @article{Kolathaya2018, title = {Input-to-state safety with control barrier functions}, author = {Shishir Kolathaya and Aaron D. James}, url = {http://www.rbccps.org/wp-content/uploads/2018/08/08405547.pdf}, doi = {10.1109/LCSYS.2018.2853698}, year = {2018}, date = {2018-07-06}, journal = {IEEE Control Systems Letters}, volume = {3}, number = {1}, pages = {108-113}, abstract = {This letter presents a new notion of input-to-state safe control barrier functions (ISSf-CBFs), which ensure safety of nonlinear dynamical systems under input disturbances. Similar to how safety conditions are specified in terms of forward invariance of a set, input-to-state safety conditions are specified in terms of forward invariance of a slightly larger set. In this context, invariance of the larger set implies that the states stay either inside or very close to the smaller safe set; and this closeness is bounded by the magnitude of the disturbances. The main contribution of the letter is the methodology used for obtaining a valid ISSf-CBF, given a control barrier function. The associated universal control law will also be provided. Towards the end, we will study unified quadratic programs that combine control Lyapunov functions and ISSf-CBFs in order to obtain a single control law that ensures both safety and stability in systems with input disturbances.}, keywords = {Autonomous Systems}, pubstate = {published}, tppubtype = {article} } This letter presents a new notion of input-to-state safe control barrier functions (ISSf-CBFs), which ensure safety of nonlinear dynamical systems under input disturbances. Similar to how safety conditions are specified in terms of forward invariance of a set, input-to-state safety conditions are specified in terms of forward invariance of a slightly larger set. In this context, invariance of the larger set implies that the states stay either inside or very close to the smaller safe set; and this closeness is bounded by the magnitude of the disturbances. The main contribution of the letter is the methodology used for obtaining a valid ISSf-CBF, given a control barrier function. The associated universal control law will also be provided. Towards the end, we will study unified quadratic programs that combine control Lyapunov functions and ISSf-CBFs in order to obtain a single control law that ensures both safety and stability in systems with input disturbances. |
| 41. | Ramesh, Rakshit; Acharya, Srikrishna; Rajaraman, Vasanth; Babu, Arun; Joglekar, Ashish; Sharma, Abhay; Amrutur, Bharadwaj; Namekar, Prashant Interoperable middleware for smartcities - Streetlighting on LoRaWAN as a case study Presentation 07.01.2018. Abstract | BibTeX | Tags: Smart City | Links: @misc{Ramesh2018, title = {Interoperable middleware for smartcities - Streetlighting on LoRaWAN as a case study}, author = {Rakshit Ramesh and Srikrishna Acharya and Vasanth Rajaraman and Arun Babu and Ashish Joglekar and Abhay Sharma and Bharadwaj Amrutur and Prashant Namekar}, url = {http://www.rbccps.org/wp-content/uploads/2018/08/AnInteroperableMiddleware.pdf}, year = {2018}, date = {2018-01-07}, booktitle = {10th International Conference on Communication Systems and Networks (COMSNETS), 03.-07.01.18, Bangalore}, abstract = {A smart city, is like every other organism a structured and organized entity. An organism comprises of a brain that performs its tasks via its appendages, just as smart cities should. However the brain needs a spine through which it communicates information to its appendages, becomes a point of confluence of different sensory and actuator pathways and facilitates activities. We herein put forth our work involving the building of such a spine for a smart city, and focus on the last mile communication aspects, especially using an LPWAN network and an implementation example with smart streetlights.}, keywords = {Smart City}, pubstate = {published}, tppubtype = {presentation} } A smart city, is like every other organism a structured and organized entity. An organism comprises of a brain that performs its tasks via its appendages, just as smart cities should. However the brain needs a spine through which it communicates information to its appendages, becomes a point of confluence of different sensory and actuator pathways and facilitates activities. We herein put forth our work involving the building of such a spine for a smart city, and focus on the last mile communication aspects, especially using an LPWAN network and an implementation example with smart streetlights. |
| 42. | Kumaar, Saumya; Navaneethkrishnan, B; Mannar, Sumedh; Omkar, Subbarama N JuncNet: A deep neural network for road junction disambiguation for autonomous vehicles Journal Article arXiv: Computer Science, 2018. Abstract | BibTeX | Tags: Autonomous Systems | Links: @article{Kumaar2018, title = {JuncNet: A deep neural network for road junction disambiguation for autonomous vehicles}, author = {Saumya Kumaar and B. Navaneethkrishnan and Sumedh Mannar and Subbarama N. Omkar}, url = {http://www.rbccps.org/wp-content/uploads/2018/12/1809.01011.pdf}, year = {2018}, date = {2018-08-31}, journal = {arXiv: Computer Science}, abstract = {With a great amount of research going on in the field of autonomous vehicles or self-driving cars, there has been considerable progress in road detection and tracking algorithms. Most of these algorithms use GPS to handle road junctions and its subsequent decisions. However, there are places in the urban environment where it becomes difficult to get GPS fixes which render the junction decision handling erroneous or possibly risky. Vision-based junction detection, however, does not have such problems. This paper proposes a novel deep convolutional neural network architecture for disambiguation of junctions from roads with a high degree of accuracy. This network is benchmarked against other well known classifying network architectures like AlexNet and VGGnet. Further, we discuss a potential road navigation methodology which uses the proposed network model. We conclude by performing an experimental validation of the trained network and the navigational method on the roads of the Indian Institute of Science (IISc). }, keywords = {Autonomous Systems}, pubstate = {published}, tppubtype = {article} } With a great amount of research going on in the field of autonomous vehicles or self-driving cars, there has been considerable progress in road detection and tracking algorithms. Most of these algorithms use GPS to handle road junctions and its subsequent decisions. However, there are places in the urban environment where it becomes difficult to get GPS fixes which render the junction decision handling erroneous or possibly risky. Vision-based junction detection, however, does not have such problems. This paper proposes a novel deep convolutional neural network architecture for disambiguation of junctions from roads with a high degree of accuracy. This network is benchmarked against other well known classifying network architectures like AlexNet and VGGnet. Further, we discuss a potential road navigation methodology which uses the proposed network model. We conclude by performing an experimental validation of the trained network and the navigational method on the roads of the Indian Institute of Science (IISc). |
| 43. | Vaidhiyan, Nidhin K; Sundaresan, Rajesh Learning to detect an oddball target Journal Article IEEE Transactions on Information Theory, 64 (2), pp. 831-852, 2018. Abstract | BibTeX | Tags: Electrical Communications Engineering | Links: @article{Vaidhiyan2018, title = {Learning to detect an oddball target}, author = {Nidhin K. Vaidhiyan and Rajesh Sundaresan}, doi = {10.1109/TIT.2017.2778264}, year = {2018}, date = {2018-02-28}, journal = {IEEE Transactions on Information Theory}, volume = {64}, number = {2}, pages = {831-852}, abstract = {We consider the problem of detecting an odd process among a group of Poisson point processes, all having the same rate except the odd process. The actual rates of the odd and non-odd processes are unknown to the decision maker. We consider a time-slotted sequential detection scenario where, at the beginning of each slot, the decision maker can choose which process to observe during that time slot. We are interested in policies that satisfy a given constraint on the probability of false detection. We propose a variation on a sequential policy based on the generalised likelihood ratio statistic. The policy, via suitable thresholding, can be made to satisfy the given constraint on the probability of false detection. Furthermore, we show that the proposed policy is asymptotically optimal in terms of the conditional expected stopping time among all policies that satisfy the constraint on the probability of false detection. The asymptotic is as the probability of false detection is driven to zero. We apply our results to a particular visual search experiment studied recently by neuroscientists. Our model suggests a neuronal dissimilarity index for the visual search task. The neuronal dissimilarity index, when applied to visual search data from the particular experiment, correlates strongly with the behavioural data. However, the new dissimilarity index performs worse than some previously proposed neuronal dissimilarity indices. We explain why this may be attributed to some experiment conditions.}, keywords = {Electrical Communications Engineering}, pubstate = {published}, tppubtype = {article} } We consider the problem of detecting an odd process among a group of Poisson point processes, all having the same rate except the odd process. The actual rates of the odd and non-odd processes are unknown to the decision maker. We consider a time-slotted sequential detection scenario where, at the beginning of each slot, the decision maker can choose which process to observe during that time slot. We are interested in policies that satisfy a given constraint on the probability of false detection. We propose a variation on a sequential policy based on the generalised likelihood ratio statistic. The policy, via suitable thresholding, can be made to satisfy the given constraint on the probability of false detection. Furthermore, we show that the proposed policy is asymptotically optimal in terms of the conditional expected stopping time among all policies that satisfy the constraint on the probability of false detection. The asymptotic is as the probability of false detection is driven to zero. We apply our results to a particular visual search experiment studied recently by neuroscientists. Our model suggests a neuronal dissimilarity index for the visual search task. The neuronal dissimilarity index, when applied to visual search data from the particular experiment, correlates strongly with the behavioural data. However, the new dissimilarity index performs worse than some previously proposed neuronal dissimilarity indices. We explain why this may be attributed to some experiment conditions. |
| 44. | Ashwin, K P; Ghosal, Ashitava Mathematical model for pressure–deformation relationship of miniaturized McKibben actuators Conference Proceedings of the 3rd International and 18th National Conference on Machines and Mechanisms (iNaCoMM), 13.-15.12.17, Mumbai, 2018. Abstract | BibTeX | Tags: Walking Robot | Links: @conference{Ashwin2018, title = {Mathematical model for pressure–deformation relationship of miniaturized McKibben actuators}, author = {K. P. Ashwin and Ashitava Ghosal}, doi = {10.1007/978-981-10-8597-0_23}, year = {2018}, date = {2018-08-29}, booktitle = {Proceedings of the 3rd International and 18th National Conference on Machines and Mechanisms (iNaCoMM), 13.-15.12.17, Mumbai}, journal = {Proceedings of the 3rd International and 18th National Conference on Machines and Mechanisms (iNaCoMM), 13.-15.12.17, Mumbai}, abstract = {A McKibben actuator/Pneumatic Artificial Muscle (PAM) is a soft actuator which has great potential in the field of bioinspired robotics. Miniaturized versions of PAMs or MPAMs of less than 1.5 mm diameter are ideal actuators for developing surgical devices due to their compliance and high power-to-weight ratio. Accurate mathematical model to represent the mechanics of PAM is an ongoing research. This paper develops a mathematical model which relates the input pressure to end-point deformation of a fabricated MPAM without external loading. The developed theoretical model is validated against experimental data for MPAM of lengths 60 and 70 mm. The model predicts the deformation of MPAM with standard error of less than 10%. The model is also able to predict the locking angle of 54.7∘ at higher pressures which is a distinct characteristic of McKibben actuators.}, keywords = {Walking Robot}, pubstate = {published}, tppubtype = {conference} } A McKibben actuator/Pneumatic Artificial Muscle (PAM) is a soft actuator which has great potential in the field of bioinspired robotics. Miniaturized versions of PAMs or MPAMs of less than 1.5 mm diameter are ideal actuators for developing surgical devices due to their compliance and high power-to-weight ratio. Accurate mathematical model to represent the mechanics of PAM is an ongoing research. This paper develops a mathematical model which relates the input pressure to end-point deformation of a fabricated MPAM without external loading. The developed theoretical model is validated against experimental data for MPAM of lengths 60 and 70 mm. The model predicts the deformation of MPAM with standard error of less than 10%. The model is also able to predict the locking angle of 54.7∘ at higher pressures which is a distinct characteristic of McKibben actuators. |
| 45. | Singla, Abhik; Padakandla, Sindhu; Bhatnagar, Shalabh Memory-based deep reinforcement learning for obstacle avoidance in UAV with limited environment knowledge Journal Article arXiv: Computer Science, 2018. Abstract | BibTeX | Tags: Drones | Links: @article{Singla2018b, title = {Memory-based deep reinforcement learning for obstacle avoidance in UAV with limited environment knowledge}, author = {Abhik Singla and Sindhu Padakandla and Shalabh Bhatnagar}, url = {http://www.rbccps.org/wp-content/uploads/2018/12/1811.03307.pdf}, year = {2018}, date = {2018-11-08}, journal = {arXiv: Computer Science}, abstract = {This paper presents our method for enabling a UAV quadrotor, equipped with a monocular camera, to autonomously avoid collisions with obstacles in unstructured and unknown indoor environments. When compared to obstacle avoidance in ground vehicular robots, UAV navigation brings in additional challenges because the UAV motion is no more constrained to a well-defined indoor ground or street environment. Horizontal structures in indoor and outdoor environments like decorative items, furnishings, ceiling fans, sign-boards, tree branches etc., also become relevant obstacles unlike those for ground vehicular robots. Thus, methods of obstacle avoidance developed for ground robots are clearly inadequate for UAV navigation. Current control methods using monocular images for UAV obstacle avoidance are heavily dependent on environment information. These controllers do not fully retain and utilize the extensively available information about the ambient environment for decision making. We propose a deep reinforcement learning based method for UAV obstacle avoidance (OA) and autonomous exploration which is capable of doing exactly the same. The crucial idea in our method is the concept of partial observability and how UAVs can retain relevant information about the environment structure to make better future navigation decisions. Our OA technique uses recurrent neural networks with temporal attention and provides better results compared to prior works in terms of distance covered during navigation without collisions. In addition, our technique has a high inference rate (a key factor in robotic applications) and is energy-efficient as it minimizes oscillatory motion of UAV and reduces power wastage. }, keywords = {Drones}, pubstate = {published}, tppubtype = {article} } This paper presents our method for enabling a UAV quadrotor, equipped with a monocular camera, to autonomously avoid collisions with obstacles in unstructured and unknown indoor environments. When compared to obstacle avoidance in ground vehicular robots, UAV navigation brings in additional challenges because the UAV motion is no more constrained to a well-defined indoor ground or street environment. Horizontal structures in indoor and outdoor environments like decorative items, furnishings, ceiling fans, sign-boards, tree branches etc., also become relevant obstacles unlike those for ground vehicular robots. Thus, methods of obstacle avoidance developed for ground robots are clearly inadequate for UAV navigation. Current control methods using monocular images for UAV obstacle avoidance are heavily dependent on environment information. These controllers do not fully retain and utilize the extensively available information about the ambient environment for decision making. We propose a deep reinforcement learning based method for UAV obstacle avoidance (OA) and autonomous exploration which is capable of doing exactly the same. The crucial idea in our method is the concept of partial observability and how UAVs can retain relevant information about the environment structure to make better future navigation decisions. Our OA technique uses recurrent neural networks with temporal attention and provides better results compared to prior works in terms of distance covered during navigation without collisions. In addition, our technique has a high inference rate (a key factor in robotic applications) and is energy-efficient as it minimizes oscillatory motion of UAV and reduces power wastage. |
| 46. | Diddigi, Raghuram Bharadwaj; Prabuchandran, K J; Bhatnagar, Shalabh Novel sensor scheduling scheme for intruder tracking in energy efficient sensor networks Journal Article IEEE Wireless Communications Letters, pp. 1-4, 2018. Abstract | BibTeX | Tags: Control and Optimisation | Links: @article{Diddigi2018, title = {Novel sensor scheduling scheme for intruder tracking in energy efficient sensor networks}, author = {Raghuram Bharadwaj Diddigi and K. J. Prabuchandran and Shalabh Bhatnagar}, url = {http://www.rbccps.org/wp-content/uploads/2018/08/08314081.pdf}, doi = {10.1109/LWC.2018.2814576}, year = {2018}, date = {2018-03-12}, journal = {IEEE Wireless Communications Letters}, pages = {1-4}, abstract = {We consider the problem of tracking an intruder using a network of wireless sensors. For tracking the intruder at each instant, the optimal number and the right configuration of sensors has to be powered. As powering the sensors consumes energy, there is a trade off between accurately tracking the position of the intruder at each instant and the energy consumption of sensors. This problem has been formulated in the framework of Partially Observable Markov Decision Process (POMDP). Even for the state-of-the-art algorithm in the literature, the curse of dimensionality renders the problem intractable. In this paper, we formulate the Intrusion Detection (ID) problem with a suitable state-action space in the framework of POMDP and develop a Reinforcement Learning (RL) algorithm utilizing the Upper Confidence Tree Search (UCT) method to solve the ID problem. Through simulations, we show that our algorithm performs and scales well with the increasing state and action spaces.}, keywords = {Control and Optimisation}, pubstate = {published}, tppubtype = {article} } We consider the problem of tracking an intruder using a network of wireless sensors. For tracking the intruder at each instant, the optimal number and the right configuration of sensors has to be powered. As powering the sensors consumes energy, there is a trade off between accurately tracking the position of the intruder at each instant and the energy consumption of sensors. This problem has been formulated in the framework of Partially Observable Markov Decision Process (POMDP). Even for the state-of-the-art algorithm in the literature, the curse of dimensionality renders the problem intractable. In this paper, we formulate the Intrusion Detection (ID) problem with a suitable state-action space in the framework of POMDP and develop a Reinforcement Learning (RL) algorithm utilizing the Upper Confidence Tree Search (UCT) method to solve the ID problem. Through simulations, we show that our algorithm performs and scales well with the increasing state and action spaces. |
| 47. | Jungers, Raphael M; Kundu, Atreyee; Heemels, Maurice Observability and controllability analysis of linear systems subject to data losses Journal Article IEEE Transactions on Automatic Control, 63 (10), pp. 3361-3376, 2018. Abstract | BibTeX | Tags: Control and Optimisation | Links: @article{Jungers2018, title = {Observability and controllability analysis of linear systems subject to data losses}, author = {Raphael M. Jungers and Atreyee Kundu and Maurice Heemels}, url = {http://www.rbccps.org/wp-content/uploads/2018/12/08170282.pdf}, doi = {10.1109/TAC.2017.2781374}, year = {2018}, date = {2018-10-31}, journal = {IEEE Transactions on Automatic Control}, volume = {63}, number = {10}, pages = {3361-3376}, abstract = {We provide algorithmically verifiable necessary and sufficient conditions for fundamental system theoretic properties of discrete-time linear, systems subject to data losses. More precisely, the systems in our modeling framework are subject to disruptions (data losses) in the feedback loop, where the set of possible data loss sequences is captured by an automaton. As such, the results are applicable in the context of shared (wireless) communication networks and/or embedded architectures where some information on the data loss behavior is available a priori . We propose an algorithm for deciding observability (or the absence of it) for such systems, and show how this algorithm can be used also to decide other properties including constructibility, controllability, reachability, null-controllability, detectability, and stabilizability by means of relations that we establish among these properties. The main apparatus for our analysis is the celebrated Skolem's Theorem from Linear Algebra. Moreover, we study the relation between the model adopted in this paper and a previously introduced model where, instead of allowing dropouts in the feedback loop, one allows for time-varying delays.}, keywords = {Control and Optimisation}, pubstate = {published}, tppubtype = {article} } We provide algorithmically verifiable necessary and sufficient conditions for fundamental system theoretic properties of discrete-time linear, systems subject to data losses. More precisely, the systems in our modeling framework are subject to disruptions (data losses) in the feedback loop, where the set of possible data loss sequences is captured by an automaton. As such, the results are applicable in the context of shared (wireless) communication networks and/or embedded architectures where some information on the data loss behavior is available a priori . We propose an algorithm for deciding observability (or the absence of it) for such systems, and show how this algorithm can be used also to decide other properties including constructibility, controllability, reachability, null-controllability, detectability, and stabilizability by means of relations that we establish among these properties. The main apparatus for our analysis is the celebrated Skolem's Theorem from Linear Algebra. Moreover, we study the relation between the model adopted in this paper and a previously introduced model where, instead of allowing dropouts in the feedback loop, one allows for time-varying delays. |
| 48. | Karanjkar, Neha; Desai, Madhav; Bhatnagar, Shalabh On continuous-space embedding of discrete-parameter queueing systems Journal Article arXiv: Computer Science, 2018. Abstract | BibTeX | Tags: Control and Optimisation | Links: @article{Karanjkar2018c, title = {On continuous-space embedding of discrete-parameter queueing systems}, author = {Neha Karanjkar and Madhav Desai and Shalabh Bhatnagar}, url = {http://www.rbccps.org/wp-content/uploads/2018/12/1606.02900.pdf}, year = {2018}, date = {2018-02-12}, journal = {arXiv: Computer Science}, abstract = {Motivated by the problem of discrete-parameter simulation optimization (DPSO) of queueing systems, we consider the problem of embedding the discrete parameter space into a continuous one so that descent-based continuous-space methods could be directly applied for efficient optimization. We show that a randomization of the simulation model itself can be used to achieve such an embedding when the objective function is a long-run average measure. Unlike spatial interpolation, the computational cost of this embedding is independent of the number of parameters in the system, making the approach ideally suited to high-dimensional problems. We describe in detail the application of this technique to discrete-time queues for embedding queue capacities, number of servers and server-delay parameters into continuous space and empirically show that the technique can produce smooth interpolations of the objective function. Through an optimization case-study of a queueing network with 10^7 design points, we demonstrate that existing continuous optimizers can be effectively applied over such an embedding to find good solutions. }, keywords = {Control and Optimisation}, pubstate = {published}, tppubtype = {article} } Motivated by the problem of discrete-parameter simulation optimization (DPSO) of queueing systems, we consider the problem of embedding the discrete parameter space into a continuous one so that descent-based continuous-space methods could be directly applied for efficient optimization. We show that a randomization of the simulation model itself can be used to achieve such an embedding when the objective function is a long-run average measure. Unlike spatial interpolation, the computational cost of this embedding is independent of the number of parameters in the system, making the approach ideally suited to high-dimensional problems. We describe in detail the application of this technique to discrete-time queues for embedding queue capacities, number of servers and server-delay parameters into continuous space and empirically show that the technique can produce smooth interpolations of the objective function. Through an optimization case-study of a queueing network with 10^7 design points, we demonstrate that existing continuous optimizers can be effectively applied over such an embedding to find good solutions. |
| 49. | Sharma, Abhay; Murthy, Chandra R On finding a subset of non-defective items from a large population Journal Article IEEE Transactions on Signal Processing, 66 (21), pp. 5762-5775, 2018. BibTeX | Tags: Electrical Communications Engineering | Links: @article{Sharma2018, title = {On finding a subset of non-defective items from a large population}, author = {Abhay Sharma and Chandra R. Murthy}, url = {http://www.rbccps.org/wp-content/uploads/2018/12/08470136.pdf}, doi = {10.1109/TSP.2018.2871441}, year = {2018}, date = {2018-11-01}, journal = {IEEE Transactions on Signal Processing}, volume = {66}, number = {21}, pages = {5762-5775}, keywords = {Electrical Communications Engineering}, pubstate = {published}, tppubtype = {article} } |
| 50. | Joglekar, Ashish; Hegde, Balachandra Online I-V Tracer for per string monitoring and maintenance of PV panels Conference Proceedings of the 44th Annual Conference of the IEEE Industrial Electronics Society (IECON), 21.-23.10.18, Washington, D.C. (USA), 2018. Abstract | BibTeX | Tags: Smart City | Links: @conference{Joglekar2018b, title = {Online I-V Tracer for per string monitoring and maintenance of PV panels}, author = {Ashish Joglekar and Balachandra Hegde}, url = {http://www.rbccps.org/wp-content/uploads/2019/05/08591616.pdf}, doi = {10.1109/IECON.2018.8591616}, year = {2018}, date = {2018-12-31}, booktitle = {Proceedings of the 44th Annual Conference of the IEEE Industrial Electronics Society (IECON), 21.-23.10.18, Washington, D.C. (USA)}, pages = {1890-1894}, abstract = {Large scale solar photovoltaic plants need to be monitored regularly for determining location and type of fault, cleaning schedules, operating point and performance. We propose a circuit that sits at the junction box level to provide `on demand', `online' I-V traces for series connected panels. This sparse sensing approach works on a per string basis and is therefore economical. The proposed online I-V tracer topology does not require the plant to be brought offline to obtain the I-V trace. The load's power requirement is met during the trace. The shape of the I-V trace helps determine the type of fault and localizes the fault to a specific string. The proposed solution has been tested in a practical field deployment. An analytics engine is also being developed to use the recorded I-V curve to provide optimal cleaning schedules, fault diagnosis and maintenance alerts.}, keywords = {Smart City}, pubstate = {published}, tppubtype = {conference} } Large scale solar photovoltaic plants need to be monitored regularly for determining location and type of fault, cleaning schedules, operating point and performance. We propose a circuit that sits at the junction box level to provide `on demand', `online' I-V traces for series connected panels. This sparse sensing approach works on a per string basis and is therefore economical. The proposed online I-V tracer topology does not require the plant to be brought offline to obtain the I-V trace. The load's power requirement is met during the trace. The shape of the I-V trace helps determine the type of fault and localizes the fault to a specific string. The proposed solution has been tested in a practical field deployment. An analytics engine is also being developed to use the recorded I-V curve to provide optimal cleaning schedules, fault diagnosis and maintenance alerts. |
