Robust observer-based adaptive synchronization control of uncertain nonlinear bilateral teleoperation systems under time-varying delay

Due to the practical restrictions such as uncertain dynamics, external disturbances and time-varying delays and lack of enough information about the remote environment, the performance of teleoperation systems cannot be guaranteed in most cases. However, some practical tasks such as tele-surgery conducted by the nonlinear teleoperation system require high performance. Recent research on teleoperation systems motivates us to propose a new robust adaptive control law for nonlinear bilateral teleoperation systems with time-varying delays, external disturbances and uncertain dynamics in a unified framework. To this end, a novel adaptive torque observer is developed to relax the system from force sensors. The main advantage of this paper is to design properly a mechanism, which is free from joint accelerations due to the acceleration measurement difficulty in robotic systems. Moreover, the key point of the proposed algorithm is to enhance the robust behavior of the system in the presence of various uncertainties by adding an auxiliary term in the control loop. Furthermore, the stability and the convergence of synchronization error to zero are also proven with the aid of both Lyapunov-Krasovskii function and linear matrix inequality. Simulation results emphasize on the effectiveness of the proposed Observed-based control approach in comparison with the related research.