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10th International Windsor Conference 2018: Rethinking Comfort

作者： Liu, Shichao Jin, Ming Das, Hari Prasanna Spanos, Costas J. Schiavon, Stefano Center for the Built Environment University of California BerkeleyCA United States Department of Electrical Engineering and Computer Sciences University of California BerkeleyCA United States Department of Civil and Environmental Engineering Worcester Polytechnic Institute MA United States

ISBN: (纸本)9780992895785

Existing HVAC systems involve little feedback from indoor occupants, resulting in unnecessary cooling/heating waste and high percentage of discomfort. In addition, large thermal preference variance amongst people requires the development of personal thermal comfort models, rather than group-based methodologies such as predicted mean vote (PMV). This study focuses on assessing wearable solutions with the aim to predict personal thermal preference. We collected physiological signals (e.g., skin temperature, heart rate) of 14 subjects (6 feMale and 8 Male adults) and environmental parameters (e.g., air temperature, wind speed, solar radiation, precipitation) for two weeks (at least 20 hr/d) to infer personal real-time thermal preference. The subjects reported their real-time thermal sensation and preference using cell-phones approximately every hour. We trained a Random Forest algorithm using data collected from individuals to develop a personal comfort model with the objective to predict thermal preference. The results show that subjects expressed needs for "warmer" or "cooler" conditions at about 30% (from 21% to 88%) of their daily time on average, implying the strong demand for a personalized indoor thermal comfort. In addition, the personal comfort model using Random Forest can infer individual thermal preference with a mean accuracy of 75% (53 - 93%) using physiological and environmental parameters, demonstrating the strengths of the proposed data-driven method. © 2018 Proceedings of 10th Windsor Conference: Rethinking Comfort.

关键词： Physiological models

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Approximate dynamic programming with probabilistic temporal logic constraints

arXiv

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arXiv 2018年

作者： Li, Lening Fu, Jie Robotics Engineering Program Department of Electrical and Computer Engineering Worcester Polytechnic Institute WorcesterMA01609 United States

In this paper, we develop approximate dynamic programming methods for stochastic systems modeled as Markov Decision Processes, given both soft performance criteria and hard constraints in a class of probabilistic temporal logic called Probabilistic Computation Tree Logic (PCTL). Our approach consists of two steps: First, we show how to transform a class of PCTL formulas into chance constraints that can be enforced during planning in stochastic systems. Second, by integrating randomized optimization and entropy-regulated dynamic programming, we devise a novel trajectory sampling-based approximate value iteration method to iteratively solve for an upper bound on the value function while ensuring the constraints that PCTL specifications are satisfied. Particularly, we show that by the on-policy sampling of the trajectories, a tight bound can be achieved between the upper bound given by the approximation and the true value function. The correctness and efficiency of the method are demonstrated using robotic motion planning examples. Copyright © 2018, The Authors. All rights reserved.

关键词： Stochastic systems

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A cnn accelerator on fpga using depthwise separable convolution

arXiv

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arXiv 2018年

作者： Bai, Lin Zhao, Yiming Huang, Xinming Department of Electrical and Computer Engineering Worcester Polytechnic Institute MA01609 United States

Convolutional neural networks (CNNs) have been widely deployed in the fields of computer vision and pattern recognition because of their high accuracy. However, large convolution operations are computing intensive and often require a powerful computing platform such as a Graphics Processing Unit (GPU). This makes it difficult to apply CNNs to portable devices. The state-of-the-art CNNs, such as MobileNetV2 and Xception, adopt depthwise separable convolution to replace the standard convolution for embedded platforms, which significantly reduces operations and parameters with only limited loss in accuracy. This highly structured model is very suitable for Field-Programmable Gate Array (FPGA) implementation. In this paper, a scalable high performance depthwise separable convolution optimized CNN accelerator is proposed. The accelerator can be fit into an FPGA of different sizes, provided the balancing between hardware resources and processing speed. As an example, MobileNetV2 is implemented on Arria 10 SoC FPGA, and the results show this accelerator can classify each picture from ImageNet in 3.75ms, which is about 266.6 frames per second. The FPGA design achieves 20x speedup if compared to CPU. Copyright © 2018, The Authors. All rights reserved.

关键词： Convolution

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Simulations of a birdcage coil B1+ field on a human body model for designing a 3T multichannel TMS/MRI head coil array 40

Simulations of a birdcage coil B1+ field on a human body mod...

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40th Annual International Conference of the IEEE engineering in Medicine and Biology Society, EMBC 2018

作者： Navarro De Lara, Lucia I. Rad, Laleh Golestani Makarov, Sergey N. Stockmann, Jason Wald, Lawrence L. Nummenmaa, Aapo Athinoula A. Martinos Center for Biomedical Imaging Massachusetts General Hospital CharlestownMA02129 United States Center for Biomedical Imaging Massachusetts General Hospital CharlestownMA02129 United States Department of Electrical and Computer Engineering Worcester Polytechnic Institute WorcesterMA01609 United States

ISBN: (纸本)9781538636466

This article considers a new type of integrated multichannel Transcranial Magnetic Stimulator and Magnetic Resonance Imaging (TMS/MRI) system at 3T that is currently being designed. The system will enable unprecedented spatiotemporal control of the TMS-induced electric fields (Efields) with simultaneous rapid whole-head MRI acquisition to record the brain activity. A critical design question is how TMS coil elements interact with the transmit field B1+ of the volume coil integrated in 3T MRI systems. In general, the TMS coils are not designed to have any resonant characteristics at the MRI frequency, they may potentially disturb the RF field due to the eddy currents induced. This is especially a concern with a multichannel TMS setup where the subject's head will be largely covered with the stimulation coils. Therefore, we investigated this problem by computational simulations with realistic TMS coil geometries and a birdcage transmit coil in conjunction with a human body model. We compared the B1+ interaction effects of a commercially available MR-compatible TMS coil with our coil prototype. In both cases, the results show small local changes in the transmit field B1+ of the birdcage coil. Maximal Average Specific Absorption Rate (SAR) values over 1g tissue were found to be slightly lower when the TMS elements were present. We conclude that it should be feasible and safe to use the conventional body transmit coil even when an array of TMS coils is used. © 2018 IEEE.

关键词： Phantoms Radio frequency Magnetic resonance imaging Head Standards Magnetic heads

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Controlled islanding via weak submodularity

arXiv

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arXiv 2018年

作者： Liu, Zhipeng Clark, Andrew Bushnell, Linda Kirschen, Daniel Poovendran, Radha Department of Electrical Engineering University of Washington SeattleWA98195 United States Department of Electrical and Computer Engineering Worcester Polytechnic Institute WorcesterMA01609 United States

Cascading failures typically occur following a large disturbance in power systems, such as tripping of a generating unit or a transmission line. Such failures can propagate and destabilize the entire power system, potentially leading to widespread outages. One approach to mitigate impending cascading failures is through controlled islanding, in which a set of transmission lines is deliberately tripped to partition the unstable system into several disjoint, internally stable islands. Selecting such a set of transmission lines is inherently a combinatorial optimization problem. Current approaches address this problem in two steps: first classify coherent generators into groups and then separate generator groups into different islands with minimal load-generation imbalance. These methods, however, are based on computationally expensive heuristics that do not provide optimality guarantees. In this paper, we propose a novel approach to controlled islanding based on weak submodularity. Our formulation jointly captures the minimal generator non-coherency and minimal load-generation imbalance in one objective function. We relax the problem to a formulation with bounded submodularity ratio and a matroid constraint, and propose an approximation algorithm which achieves a provable optimality bound on non-coherency and load-generation imbalance. The proposed framework is tested on IEEE 39-bus and 118-bus power systems. Copyright © 2018, The Authors. All rights reserved.

关键词： Electric lines

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Network topology mapping from partial virtual coordinates and graph geodesics

arXiv

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arXiv 2018年

作者： Jayasumana, Anura P. Paffenroth, Randy Mahindre, Gunjan Ramasamy, Sridhar Gajamannage, Kelum Department of Electrical & Computer Engineering Colorado State University Fort CollinsCO80525 United States Department of Mathematical Sciences Department of Computer Science Data Science Program Worcester Polytechnic Institute WorcesterMA01609 United States Department of Mathematical Sciences Worcester Polytechnic Institute WorcesterMA01609 United States

For many important network types (e.g., sensor networks in complex harsh environments and social networks) physical coordinate systems (e.g., Cartesian), and physical distances (e.g., Euclidean), are either difficult to discern or inapplicable. Accordingly, coordinate systems and characterizations based on hop-distance measurements, such as Topology Preserving Maps (TPMs) and Virtual-Coordinate (VC) systems are attractive alternatives to Cartesian coordinates for many network algorithms. Herein, we present an approach to recover geometric and topological properties of a network with a small set of distance measurements. In particular, our approach is a combination of shortest path (often called geodesic) recovery concepts and low-rank matrix completion, generalized to the case of hop-distances in graphs. Results for sensor networks embedded in 2-D and 3-D spaces, as well as a social networks, indicates that the method can accurately capture the network connectivity with a small set of measurements. TPM generation can now also be based on various context appropriate measurements or VC systems, as long as they characterize different nodes by distances to small sets of random nodes (instead of a set of global anchors). The proposed method is a significant generalization that allows the topology to be extracted from a random set of graph shortest paths, making it applicable in contexts such as social networks where VC generation may not be possible. Copyright © 2018, The Authors. All rights reserved.

关键词： Sensor networks

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From Swarms to Stars: Task Coverage in Robot Swarms with Connectivity Constraints

From Swarms to Stars: Task Coverage in Robot Swarms with Con...

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IEEE International Conference on Robotics and Automation (ICRA)

作者： Jacopo Panerati Luca Gianoli Carlo Pinciroli Abdo Shabah Gabriela Nicolescu Giovanni Beltrame Polytechnique Montréal Department of Computer and Software Engineering Department of Computer Science Worcester Polytechnic Institute HumanITas Solutions Montreal QC Canada

Swarm robotics carries the potential of solving complex tasks using simple devices. To do so, however, one must define distributed control algorithms capable of producing globally coordinated behaviours. We propose a methodology to address the problem of the spatial coverage of multiple tasks with a swarm of robots that must not lose global connectivity. Our methodology comprises two layers: (i) a distributed Robot Navigation Controller (RNC) is responsible for simultaneously guaranteeing connectivity and pursuit of multiple tasks; and (ii) a global Task Scheduling Controller approximates the optimal strategy for the RNC with minimal computational load. Our contributions include: (i) a qualitative analysis of the literature on connectivity assessment, (ii) our proposed methodology, (iii) simulations in a multi-physics environment, (iv) real-life robot experiments, and (v) the experimental validation of connectivity, coverage optimality, and fault-tolerance.

关键词： Task analysis Robot kinematics Navigation Eigenvalues and eigenfunctions Computational modeling Multi-robot systems

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Sampling-based approximate optimal temporal logic planning

Sampling-based approximate optimal temporal logic planning

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2017 IEEE International Conference on Robotics and Automation, ICRA 2017

作者： Li, Lening Fu, Jie Robotics Engineering Program Worcester Polytechnic Institute WorcesterMA01609 United States Robotics Engineering Program Department of Electrical and Computer Engineering Worcester Polytechnic Institute WorcesterMA01609 United States

ISBN: (纸本)9781509046331

In this paper, we propose a sampling-based policy iteration for optimal planning under temporal logic constraints. The method integrates approximate optimal control, importance sampling, and formal methods. For a subclass of linear temporal logic, the planning problem is transformed to an optimal control problem for a hybrid system where discrete transitions are triggered by linear time events in temporal logic. Instead of solving the Hamilton-Jacobi-Bellman equation, we use policy function approximation to reduce the problem into a search of an optimal weight vector that parametrizes the near-optimal policy for given bases. Then, we incorporate Model Reference Adaptive Search - an importance sampling-based optimization algorithm to perform a sample-efficient search within the parameter space of policy function approximations. Facing the discontinuity in cost function introduced by temporal logic constraints and system dynamics, we introduce 1) a rank function in formal logic specifications to enable sample-efficient search;2) specification-guided basis selection. Under mild technical assumptions, the proposed algorithm converges, with probability one, to a global approximate optimal policy that ensures the satisfaction of temporal logic constraints. The correctness and efficiency of the method are demonstrated through numerical experiments including temporal logic planning for a linear system and a nonlinear mobile robot. © 2017 IEEE.

关键词： Temporal logic

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Shape of the cloak: Formal analysis of clock skew-based intrusion detection system in controller area networks

arXiv

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arXiv 2018年

作者： Ying, Xuhang Sagong, Sang Uk Clark, Andrew Bushnell, Linda Poovendran, Radha Department of Electrical Engineering University of Washington SeattleWA98195-2500 United States Department of Electrical and Computer Engineering Worcester Polytechnic Institute WorcesterMA01609 United States

This paper presents a new masquerade attack called the cloaking attack and provides formal analyses for clock skewbased Intrusion Detection Systems (IDSs) that detect masquerade attacks in the Controller Area Network (CAN) in automobiles. In the cloaking attack, the adversary manipulates the message inter-transmission times of spoofed messages by adding delays so as to emulate a desired clock skew and avoid detection. In order to predict and characterize the impact of the cloaking attack in terms of the attack success probability on a given CAN bus and IDS, we develop formal models for two clock skew-based IDSs, i.e., the state-of-the-art (SOTA) IDS and its adaptation to the widely used Network Time Protocol (NTP), using parameters of the attacker, the detector, and the hardware platform. To the best of our knowledge, this is the first paper that provides formal analyses of clock skew-based IDSs in automotive CAN. We implement the cloaking attack on two hardware testbeds, a prototype and a real vehicle (the University of Washington (UW) EcoCAR), and demonstrate its effectiveness against both the SOTA and NTP-based IDSs. We validate our formal analyses through extensive experiments for different messages, IDS settings, and vehicles. By comparing each predicted attack success probability curve against its experimental curve, we find that the average prediction error is within 3:0% for the SOTA IDS and 5:7% for the NTP-based IDS. Copyright © 2018, The Authors. All rights reserved.

关键词： Controllers

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Erratum: “Cavity electrodynamics with Hermite interpolation: Role of symmetry and degeneracies” [J. Appl. Phys. 124, 213106 (2018)]

引用

Journal of Applied Physics 2019年第20期125卷

作者： Siddhant Pandey Sathwik Bharadwaj M. Santia M. Hodek J. D. Albrecht L. R. Ram-Mohan 1Department of Physics Worcester Polytechnic Institute Worcester Massachusetts 01609 USA 2Department of Electrical and Computer Engineering Michigan State University East Lansing Michigan 48824 USA 3Department of Electrical and Computer Engineering and Department of Mechanical Engineering Worcester Polytechnic Institute Worcester Massachusetts 01609 USA

In our original article,1 the y-axis in Figs. 3 and 4 was mislabeled as the relative error; however, it is supposed to be a logarithm of the relative error. The

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