On Control Design Of Bilateral Teleoperation Systems With Time Delays

With the rapid development of space technology, marine technology and atomic energy technology, advanced robots working under dangerous and unknown environments are urgent and greatly required. However, It is not a reality that fully autonomous robot can work flexibly in such environments. Hence, lots of researchers pay attention to teleoperation systems which can extend people’s ability to manipulate remote devices. Communication delays are inevitable in teleoperation systems, they can severely impair the performance of teleoperation systems, and sometimes they would cause instability of the closed-loop systems. Hence, It is of theoretical significance and practical value to work on the control design of bilateral systems with time delays.Aimed to improve stability and transparency of teleoperation systems, the dissertation developed various control strategies for teleoperation systems with time delays by using Youla parameterization, LMI technology, and optimal technology, based on Lyapunov functional methods. The main contents are as follows:1) As for linear teleoperation systems with constant communication delays, a stabilizing control framework is proposed by using the quadratically invariance of decentralized controller in teleoperation systems. This control framework can guarantee the stability even when the communication delays switch from zero to some constant. The output signals generated from the external forces are separated, and are selected to be reference signals for controllers. No assumption is required for operator’s forces and environmental forces.2) As for linear teleoperation systems with time-varying communication delays and with non-passive human forces and environmental forces, a guaranteed cost control strategy is proposed. The delay-dependent stability criterion and the sub-optimal controller are deduced. The transparency is guaranteed in three aspects: position tracking performance, velocity tracking performance and force tracking performance.3) As for nonlinear teleoperation systems with constant communication delays, an acceleration feedback control strategy is proposed. The input-state-stability criterion of the closed-loop system is given. The acceleration information of the slave is used in the master controller, and the position error between the master and the slave plus nonlinear damping is applied to the slave controller, then the contact instability is avoided and the passivity assumption for human forces and environmental forces is removed. Compared with other methods in the literature, the proposed strategy can improve the synchronization speed and the tracking performance.4) As for nonlinear teleoperation systems with time-varying communication delays, an acceleration feedback control strategy is proposed. The small gain condition for the stability of the closed-loop system is given. The acceleration information of the slave is used in the master controller, and the position error between the master and the slave plus linear damping is applied to the slave controller, the stability of the closed-loop system with time-varying delays which is bounded by upper and lower bounds is guaranteed.