Transparency and Tuning of Wave-Based Bilateral Teleoperation Systems

Abstract

When force feedback is employed in bilateral teleoperation of a robotic system, classical control techniques can become unstable in the presence of communication latency. An established solution to this problem employs the scattering transformation to guarantee passivity. This transformation requires the selection of a wave impedance parameter that strongly affects transparency to the operator. It is widely recognized that a large impedance value is well suited to contact tasks and a low value is preferable for free motion. However, in any realistic manipulation task, both forms of motion will exist during at least a portion of the task. Some amount of free motion will typically be necessary during approach to the contact site; and, even after transition to contact has occurred, free motion considerations will still dominate on the axes parallel to the manipulated surface. This paper explores analytically this tradeoff, proposing an optimal solution from the linear systems theory. Choice of controller gains is additionally discussed. Attention is also given to the feedback-passivized scheme of Chopra et al. , which is shown to be free of the fundamental wave impedance tradeoff that dominates the classical wave-based approach.