Allowable Transmission Delay Research Articles

New delay-dependent position/force hybrid controller design for uncertain telerobotics without force sensors

In this article, a new position/force hybrid control strategy is proposed for a class of uncertain bilateral telerobotics systems under time-varying communication delays. This control approach features the capability of removing the use of force sensors and relaxing the assumption on external forces. Specially, the proposed terminal sliding mode (TSM)-based force observer can estimate human force and environment force in a fixed time by applying a variable exponent coefficient, which effectively avoids the temporal problems of other existing force observers. By embedding the estimated force information, corresponding position/force hybrid controller is designed to ensure transparency and stability of system, which can be evaluated by the position synchronization in the slave and the force repeated in the master. Furthermore, by selecting Lyapunov–Krasovskii functional, it proves the stability of the bilateral telerobotics system under particular linear matrix inequality (LMI) conditions. The proposed stability criterion can serve to calculate the maximum allowable transmission delay with the given controller parameters; thus, the conservativeness is reduced. Finally, simulation comparison results and experimental results demonstrate the superior performance of the proposed position/force hybrid controller under different external forces.

Global output feedback sampled‐data stabilization for upper‐triangular nonlinear systems with improved maximum allowable transmission delay

SummaryThis paper addresses the problem of output feedback sampled‐data stabilization for upper‐triangular nonlinear systems with improved maximum allowable transmission delay. A class of hybrid systems are firstly introduced. The transmission delay may be larger than the sampling period. Then, sufficient conditions are proposed to guarantee global exponential stability of the hybrid systems. Based on these sufficient conditions and a linear continuous‐discrete observer, an output feedback control law is presented to globally exponentially stabilize the feedforward nonlinear system. The improved maximum allowable transmission delay is also given. The results are also extended to output feedback sampled‐data stabilization for lower‐triangular nonlinear systems. Finally, illustrative examples are used to verify the effectiveness of the proposed design methods. Copyright © 2016 John Wiley & Sons, Ltd.

Computation of robust stability bounds for networked systems with varying delays

This paper is concerned with the computation of robust stability bounds for networked controlled systems with uncertain, varying, bounded transmission delays. Given the feedback controller, the maximum allowable transmission delay is computed based on a linear matrix inequality (LMI)-constrained non-linear optimisation problem. Since certain variations of the posed problem, demand a nominally stable closed-loop system, a controller-synthesis procedure is also presented. The computation of the stabilising controller is based on a delay-dependent LMI-feasibility problem. The derived robust stability bounds are compared in simulation studies.

Real-time data aggregation in contention-based wireless sensor networks

We investigate the problem of delay constrained maximal information collection for CSMA-based wireless sensor networks. We study how to allocate the maximal allowable transmission delay at each node, such that the amount of information collected at the sink is maximized and the total delay for the data aggregation is within the given bound. We formulate the problem by using dynamic programming and propose an optimal algorithm for the optimal assignment of transmission attempts. Based on the analysis of the optimal solution, we propose a distributed greedy algorithm. It is shown to have a similar performance as the optimal one.

Computer graphics eye‐animation and feeling of gaze line

AbstractIn a teleconferencing system with realistic sensations, human images are generated by computer graphics (CG). This requires animating natural eye movement with CG. This paper describes a real‐time animation technique to generate blinking and gaze shift, while still considering convergence using a graphic workstation. Moreover, the feeling of eye contract is evaluated using this animation. In this experiment, the gaze generated by CG using two‐dimensional (2‐D) or 3‐D display is evaluated subjectively and compared with the gaze of an actual person. Also, an experiment is performed on the time required for perception of eye contact when the eyes of the CG image are moving. Then, a real‐time CG eyeanimation system combined with an eye‐movement detector is described. Also, the allowable transmission delay time when using this system is evaluated subjectively.