Discrete-time Linear Quadratic Gaussian Control for Teleoperation Under Communication Time Delay

Prior relevant research in bilateral teleoperation has mainly yielded control algorithms that sacrifice performance in order to guarantee robust stability in the presence of communication latency. In contrast, in this paper we propose a multimodel predictive-type control approach based on the discrete-time linear quadratic Gaussian (LQG) control that delivers a stable transparent response in the presence of constant delay. Separate controllers are designed for different phases of operation, i.e., free motion/soft contact and contact with rigid environments, with switching between these mode-based controllers occurring according to the identified contact mode. The treatment of the problem in the discrete-time domain allows for the development of a finite dimension state-space model that explicitly encompasses the time delay. Performance objectives such as position tracking and tool impedance shaping for free motion/soft contact, as well as position and force tracking for contact with rigid environments, are incorporated into the LQG control design framework. The robustness of the controller with respect to uncertainty in the system parameters is examined via the Nyquist analysis. Simulation and experimental results demonstrate that the proposed control technique is highly effective in providing a stable transparent interface for teleoperation under time delay.