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IEEE International Conference on robotics and Automation (ICRA)

作者： Lening Li Jie Fu Robotics Engineering Program Worcester Polytechnic Institute Worcester MA US

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.

关键词： Planning Approximation algorithms Trajectory Function approximation Nonlinear systems Optimal control Automata

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Topological Approximate Dynamic programming under Temporal Logic Constraints

Topological Approximate Dynamic Programming under Temporal L...

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IEEE Annual Conference on Decision and Control

作者： Lening Li Jie Fu Robotics Engineering Program Worcester Polytechnic Institute Worcester MA USA

ISBN: (数字)9781728113982

ISBN: (纸本)9781728113999

In this paper, we develop a model-free approximate dynamic programming method for stochastic systems modeled as Markov decision processes to maximize the probability of satisfying high-level system specifications expressed in a subclass of temporal logic formulas-syntactically co-safe linear temporal logic. Our proposed method includes two steps: First, we decompose the planning problem into a sequence of sub-problems based on the topological property of the task automaton which is translated from a temporal logic formula. Second, we extend a model-free approximate dynamic programming method to solve value functions, one for each state in the task automaton, in an order reverse to the causal dependency. Particularly, we show that the run-time of the proposed algorithm does not grow exponentially with the size of specifications. The correctness and efficiency of the algorithm are demonstrated using a robotic motion planning example.

关键词： Task analysis Planning Dynamic programming Markov processes Automata Approximation algorithms Function approximation

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Novel EOD robot design with dexterous gripper and intuitive teleoperation

Novel EOD robot design with dexterous gripper and intuitive ...

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Proceedings of the Biannual World Automation Congress

作者： Matthew W. Carey Eric M. Kurz Joshua D. Matte Timothy D. Perrault Taskin Padir Robotics Engineering Program Worcester Polytechnic Institute Worcester MA USA

This paper details the design and implementation of an intelligent explosive ordnance disposal robot to provide law enforcement agencies with a cost effective and reliable robotic platform. The key features of the robot include an intuitive user interface which provides additional sensor feedback and enhanced visual awareness compared to existing systems, an on-board three degree of freedom manipulator arm providing an enlarged workspace, and a dexterous gripper allowing for the removal of blasting caps. The flexible and modular robot design utilizes commercial off-the-shelf components for ease of maintenance and repairs. The robot provides a safe distance threat assessment and increased capacity for explosive ordnance disposal, improving the effectiveness of bomb disposal teams. The robot's low-cost, intuitive operation and ease-of-maintenance promote its widespread appeal, thereby saving the lives of both law enforcement personnel and civilians.

关键词： Grippers Robot kinematics Cameras Explosives Robot vision systems

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Adaptive motion control for a differentially driven semi-autonomous wheelchair platform

Adaptive motion control for a differentially driven semi-aut...

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International Conference on Advanced robotics (ICAR)

作者： Dmitry A. Sinyukov Taşkın Padır Robotics Engineering Program Worcester Polytechnic Institute Worcester MA USA

Motorized wheelchairs are systems with changing parameters: rolling friction which depends on the ground surface, center of gravity and even the total mass of the system may vary. This affects the performance of PID controllers normally used for wheelchair velocity control. This paper presents an adaptive controller with online parameter estimation for the motion control of a semi-autonomous robotic wheelchair platform. The proposed controller accepts a second-order trajectory as an input rather then the desired velocity at each moment in time. Mathematical and computer models are developed for the wheelchair and the controller. Four simulation experiments with different initial conditions are demonstrated and analyzed in this work based on a custom developed MATLAB/Simulink ® framework for wheelchair dynamic modeling and visualization. Advantages and limitations of the proposed approach are discussed.

关键词： Wheelchairs Adaptation models Mobile robots Mathematical model Wheels Friction

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Active Telepresence Assistance for Supervisory Control: A User Study with a Multi-Camera Tele-Nursing Robot

Active Telepresence Assistance for Supervisory Control: A Us...

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IEEE International Conference on robotics and Automation (ICRA)

作者： Alexandra Valiton Hannah Baez Naomi Harrison Justine Roy Zhi Li Robotics Engineering Program Worcester Polytechnic Institute Worcester MA USA

Supervisory control of a humanoid robot in a manipulation task requires coordination of remote perception with robot action, which becomes more demanding with multiple moving cameras available for task supervision. We explore the use of autonomous camera control and selection to reduce operator workload and improve task performance in a supervisory control task. We design a novel approach to autonomous camera selection and control, and evaluate the approach in a user study which revealed that autonomous camera control does improve task performance and operator experience, but autonomous camera selection requires further investigation to benefit the operator’s confidence and maintain trust in the robot autonomy.

关键词： Telepresence Automation Robot kinematics Conferences Robot vision systems Humanoid robots Supervisory control

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Compositional planning in Markov decision processes: Temporal abstraction meets generalized logic composition

Compositional planning in Markov decision processes: Tempora...

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American Control Conference

作者： Xuan Liu Jie Fu Robotics Engineering Program Worcester Polytechnic Institute Worcester MA USA

ISBN: (纸本)9781538679012;9781538679265

In hierarchical planning for Markov decision processes (MDPs), temporal abstraction allows planning with macro-actions that take place at different time scale in form of sequential composition. In this paper, we propose a novel approach to compositional reasoning and hierarchical planning for MDPs under co-safe temporal logic constraints. In addition to sequential composition, we introduce a composition of policies based on generalized logic composition: Given sub-policies for sub-tasks and a new task expressed as logic compositions of subtasks, a semi-optimal policy, which is optimal in planning with only sub-policies, can be obtained by simply composing sub-polices. Thus, a synthesis algorithm is developed to compute optimal policies efficiently by planning with primitive actions, policies for sub-tasks, and the compositions of sub-policies, for maximizing the probability of satisfying constraints specified in the fragment of co-safe temporal logic. We demonstrate the correctness and efficiency of the proposed method in stochastic planning examples with a single agent and multiple task specifications.

关键词： Markov chain time scales Planning Formal logic Policies Abstraction Temporal logic accuracy class

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Analyzing and modeling an IMU for use in a low-cost combined vision and inertial navigation system

Analyzing and modeling an IMU for use in a low-cost combined...

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2012 IEEE International Conference on Technologies for Practical Robot Applications, TePRA 2012

作者： Barrett, Justin M. Gennert, Michael A. Michalson, William R. Center Jr., Julian L. Robotics Engineering Department Worcester Polytechnic Institute Worcester MA United States Autonomous Exploration Inc. Andover MA United States

ISBN: (纸本)9781467308557

The automotive and videogame industries have driven the cost of Micro-Electro-Mechanical System (MEMS) accelerometers and gyroscopes down to the range of just a few dollars. Likewise, the personal computer and cell phone industries have driven the cost of relatively high-resolution camera chips down to comparably low levels. Due to these cost reductions, a low-cost robot navigation system using a combination of vision and inertial sensors would be an inexpensive and effective method of navigating without the aid of GPS signals. Vision and inertial sensors are ideally suited to work together because their error characteristics are complementary. MEMS accelerometers and gyroscopes are capable of tracking high-speed motions, but suffer from long-term drifts that make them impractical to use as standalone navigation sensors. However, using Bayesian estimation methods, vision information from a stereo camera pair can be used to correct these drift errors. Therefore, using both vision and inertial sensors in tandem can produce an accurate navigation system that can operate indoors or in other areas where GPS signals or other navigation aids are unavailable. In this paper, we present two data analysis methods that can be used to calibrate and characterize the noise that is produced by MEMS-based IMUs. © 2012 IEEE.

关键词： Inertial navigation systems

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Opportunistic Synthesis in Reactive Games under Information Asymmetry

Opportunistic Synthesis in Reactive Games under Information ...

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IEEE Annual Conference on Decision and Control

作者： Abhishek N. Kulkarni Jie Fu Robotics Engineering Program Worcester Polytechnic Institute Worcester MA USA Faculty of the Department of Electrical and Computer Engineering with affiliation to Robotics Engineering Program Worcester Polytechnic Institute Worcester MA USA

ISBN: (数字)9781728113982

ISBN: (纸本)9781728113999

Reactive synthesis is a class of methods to construct a provably-correct control system, referred to as a robot, with respect to a temporal logic specification in the presence of a dynamic and uncontrollable environment. This is achieved by modeling the interaction between the robot and its environment as a two-player zero-sum game. However, existing reactive synthesis methods assume both players to have complete and symmetrical information, which is not the case in many strategic interactions. In this paper, we use a variant of hypergames to model the interaction between the robot and its environment;where the latter has incomplete information about the specification of the robot. We propose a novel method of opportunistic synthesis defined over the hypergame model to identify a subset of hypergame states from where the robot can leverage the asymmetrical information to achieve a better outcome, which is not possible if both players have symmetrical and complete information. By assuming the environment to play a stochastic strategy in its perceived sure-winning and sure-losing regions of the game, we show that by following the opportunistic strategy, the robot is ensured to only improve the outcome of the game-measured by satisfaction of sub-specifications-whenever an opportunity becomes available. We demonstrate the correctness and optimality of this method using a robot motion planning example in the presence of an adversary.

关键词： Robots Games Task analysis Computational modeling Game theory Planning Stochastic processes

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programmable Skins based on Core-Shell Microsphere/Nanotube/Polymer Composites

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MRS Online Proceedings Library 2015年第1期1800卷 1-6页

作者： Panchapakesan, Balaji Onal, Cagdas Loomis, James Small Systems Laboratory Department of Mechanical Engineering Worcester Polytechnic Institute Worcester USA Soft Robotics Laboratory Department of Mechanical Engineering Robotics Engineering Program Worcester Polytechnic Institute Worcester USA Department of Mechanical Engineering Massachusetts Institute of Technology Cambridge USA

In this paper, we describe unique thermally responsive polymer system based on nanotube-elastomers dispersed with core-shell expanding microspheres (phase-change material). Upon thermal or infrared stimuli, liquid hydrocarbon cores encapsulated within the microspheres vaporize, expanding the surrounding shells and stretching the matrix. Microsphere transformation resulted in visible dimensional changes associated with macroscopic volume increase (>500%), reduction in density (>80%), and increase in elastic modulus (>675%). Additionally, electrically conductive nanotubes allowed for expansion dependent electrical responses. We present our new findings on expansion dependent superhydrophobicity in these materials and present some outlook and comparison of our stimuli responsive polymers with other material systems for future origami based applications.

关键词： actuator composite nanostructure

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The effect of bath temperature and agitation rate on the quench severity of 6061 aluminum in distilled water

The effect of bath temperature and agitation rate on the que...

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International Surface engineering Congress - Proceedings of the 1st Congress

作者： Fontecchio, Marco Maniruzzaman, Mohammed Sisson Jr., Richard D. Mat. Science and Engineering Program Center for Heat Treating Excellence Worcester Polytechnic Institute Worcester MA 01609

ISBN: (纸本)0871707810

A CHTE probe-quenching system, employing a 6061 aluminum probe, was quenched in distilled water while varying bath temperature and the rate of agitation. Time vs. temperature data was collected during the quench by use of an ungrounded K-type thermocouple embedded inside the probe, while cooling rates were calculated. A Quench Factor Analysis (QFA) was also performed to quantitatively classify the quench severity. The data showed an increase in maximum cooling rate as bath temperature decreased and agitation level increased. In addition, it was found that at higher levels of agitation, there was also an increase in the standard deviation of the cooling rate.

关键词： Quenching

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