Adaptive Energy Reference Time Domain Passivity Control of Teleoperation Systems in the Presence of Time Delay

The main goal of the teleoperation systems is to achieve the highest transparency possible while maintaining stability in the presence of the time delay. This paper proposes the adaptive energy reference Time Domain Passivity Approach (TDPA) to teleoperation systems with communication delays, in order to overcome the drawbacks of the conventional TDPA such as sudden force change, conservatism, and position drift. The proposed method establishes a reference energy function by estimating the passive elements of the system, i.e., eliminating the active parts. The passive elements are estimated by utilizing the Recursive Least Square (RLS) method. The controller makes the system follow the reference energy by dissipating energy with a variable damping element. Since the controller is activated once the energy decreases, it has smoother force changes than the conventional TDPA which is activated once energy gets negative. The adaptive energy reference TDPA is extended for teleoperation systems in a structure that can avoid the position drift and the conservative passivity condition of the conventional TDPA by eliminating the parallel passivity controller. The simulation results show that the adaptive energy reference TDPA reduces the force changes up to 23 percent in comparison with the conventional TDPA. In addition, the energy of the adaptive energy reference TDPA is less dissipated than the conventional TDPA which shows a less conservative behavior. Furthermore, no position drift is observed in the adaptive energy reference TDPA.