TechTalks from event: Technical session talks from ICRA 2012

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Networked Robots

  • Compensation of Packet Loss for a Network-Based Rehabilitation System Authors: Bae, Joonbum; Zhang, Wenlong; Tomizuka, Masayoshi
    In this paper, a network-based rehabilitation system is proposed to increase mobility of a rehabilitation system and to enable tele-rehabilitation. Control algorithms and rehabilitation strategies distributed at the central location (physical therapist) and the local site (patient) communicate over wireless network to realize a network-based rehabilitation system. To deal with possible packet losses over wireless network, a modified linear quadratic Gaussian (LQG) controller and a disturbance observer (DOB) are applied. The performance of the proposed system and control algorithms is verified by simulation and experiment with an actual knee rehabilitation system. The simulation and experiment results show that the network-based rehabilitation system with the proposed control schemes can generate the desired assistive torque accurately in presence of packet losses.
  • Motion Planning for Robust Wireless Networking Authors: Fink, Jonathan; Ribeiro, Alejandro; Kumar, Vijay
    We propose an architecture and algorithms for maintaining end-to-end network connectivity for autonomous teams of robots. By adopting stochastic models of point-to-point wireless communication and computing robust solutions to the network routing problem, we ensure reliable connectivity during robot movement in complex environments. We fully integrate the solution to network routing with the choice of node positions through the use of randomized motion planning techniques. Experiments demonstrate that our method succeeds in navigating a complex environment while ensuring that end-to-end communication rates meet or exceed prescribed values within a target failure tolerance.
  • Decentralised Information Gathering with Communication Costs Authors: Kassir, Abdallah; Fitch, Robert; Sukkarieh, Salah
    Advantages of decentralised decision making systems for multi-agent robotic tasks are limited by the heavy demand they impose on communication. This paper presents an approach to control communication for the LQ team problem, namely a team of agents with linear dynamics and quadratic team cost. Communication costs are added to the objective of the LQ optimal control linear matrix inequality formulation, allowing for a well-defined balancing of communication costs and team performance. Results show a reduction in communication consistent with the specified cost and in a manner that upholds team performance relative to the reduced communication footprint. The applicability of the approach has also been extended to information gathering tasks through local LQ approximations along the agents’ paths. Simulation testing on a sample two-agent problem shows a 40% reduction in communication with negligible impact on performance.
  • Decentralized Connectivity Maintenance for Networked Lagrangian Dynamical Systems Authors: Sabattini, Lorenzo; Secchi, Cristian; Chopra, Nikhil
    In order to accomplish cooperative tasks, multi-robot systems are required to communicate among each other. Thus, maintaining the connectivity of the communication graph is a fundamental issue. Connectivity maintenance has been extensively studied in the last few years, but generally considering only kinematic agents. In this paper we will introduce a control strategy that, exploiting a decentralized procedure for the estimation of the algebraic connectivity of the graph, ensures the connectivity maintenance for groups of Lagrangian systems. The control strategy is validated by means of analytical proofs and simulation results.
  • Multi-Target Tracking Using Distributed SVM Training Over Wireless Sensor Networks Authors: Kim, Woojin; YOO, Jae Hyun; Kim, H. Jin
    In this paper, we propose to use distributed support vector machine (SVM) training to solve a multi-target tracking problem in wireless sensor networks. We employ gossip-based incremental SVM to obtain the discriminant function. By gossiping the support vectors with neighboring sensor nodes, the local SVM training results can achieve the agreement of the sub-optimal discriminant planes. After training the local SVM at each node, we can calculate the posterior probability of the existence of the targets using Platt's method. By maximum a posterior (MAP), the target trajectories are estimated. In order to validate the proposed tracking framework in wireless sensor networks, we perform two different target-tracking experiments. The experimental results demonstrate that the proposed procedure provides a good estimator, and supports the feasibility of applying the distributed SVM training to the target tracking problems.
  • A Dual-Use Visible Light Approach to Integrated Communication and Localization of Underwater Robots with Application to Non-Destructive Nuclear Reactor Inspection Authors: Rust, Ian; Asada, Harry
    Visible light communication systems have gained prominence as a method for wireless underwater communications. This is because these systems are capable of long distance communications in water with high bandwidths. A requirement of visible light systems, however, is consistent line of sight to maintain a communication link. This arises from the directional nature of visible light emitters and detectors. One solution to this problem is to implement feedback control in order to “point” visible light emitters and detectors at one another. This in turn requires precise estimation of the relative locations of these two components as a feedback signal. In this work, a system is presented that uses the modulated light signal both as a medium with which to carry data and as a reference upon which to base the localization of a mobile robot. This is therefore a dual-use system, for both communication and localization. First, this paper presents the architecture of a dual-use visible light communication and localization system. The localization is carried out using an Extended Kalman Filter (EKF) algorithm. Then, a planar version of this dual-use system is tested, demonstrating the feasibility and effectiveness of the dual-use approach.