Bilateral Teleoperation over the Internet: The Time Varying Delay Problem

This paper addresses the problem of time-varying communication delay in force reflecting bilateral teleoperation. The problem is motivated by the increasing use of the Internet as a communication medium where the time delay is variable depending on factors such as congestion, bandwidth, or distance. The well-known scattering formalism introduced in [1] preserves passivity of the communication channel in general only for constant transmission delay. We demonstrate how to recover both passivity and tracking performance using a modified control architecture that incorporates time-varying gains into the scattering transformation and feedforward position control. Experimental results using a single-degree of freedom master/slave system are presented.