Naturally-Transitioning Rate-to-Force Controller Robust to Time Delay by Model-Mediated Teleoperation

In this paper a new model-mediated teleoperation framework based on rate-control input is presented. The system facilitates force feedback teleoperation and is inherently robust to severe time delays yet still provides high level of rate/force tracking fidelity. Previously published methods on model-mediated teleoperation are here extended to accept rate commands and use the slave robot´s programmed impedance as a contact model for force feedback generation. The system is designed to ensure decoupling of the control loops in case of environment changes, which also allows to cope with severe and possibly variable time delay in the communication channel. Stability and performance is analyzed and the system is shown to remain stable for finite delays. Tuning guidelines with design trade-offs are provided. The presented method is demonstrated on an experimental 1-DOF master/slave setup in a teleoperation scenario, showing stability and reference rate & force tracking performance over 2 seconds of round-trip communication delay in bilateral control.