Stabilization of delayed teleoperation systems using time domain passivity control

It is known that time delay in bilateral teleoperation can drive a system to instability. Time Domain Passivity Control (TDPC) deals with the stabilization of haptic interfaces in teleoperation using the notion of passivity directly in the continuous time variables like force and velocity. In this work, first it is shown that TDPC can be extended to stabilize the time-delayed teleoperation by considering the communication channel as an active component and then, to design passivity controllers for it on master side using a Kalman filter based recursive prediction of slave side energy. However, such a scheme is prone to large corrective impulses generated by passivity controllers as the scheme only comes into effect when the net energy goes negative, while on other time instants it stays out of the control loop in order to provide maximally transparent teleoperation. These impulses degrade the performance of teleoperator. It is thus further proposed, that the derivative of net energy should also be computed in real-time, and as soon as this term becomes negative, indicating a decline in the net energy, the passivity controllers should immediately compensate this active behavior. This forces the system to always dissipate energy and thus stop the occasional accumulation of a large amount of negative energy. In addition to that, parabolic power integration is employed to provide non-linear estimation of net energy in the communication channel.

The above developed approach is then used to stabilize time-varying delays. In order to provide a time-base for the predictor, a first order one-step ahead prediction of RTT (Round Trip Time) is used. Beta distributed and TrueTime network simulator based delays are used to evaluate the system performance. Simulation results are given showing the efficacy of the proposed approach.