Transparency-enhanced observer-based adaptive backstepping torque–position control for teleoperation systems with position error constraint and time-varying delay

Nonlinear teleoperation systems are susceptible to significant problems, including transparency, safety, stability and external torques/forces measurement. In order to deal with these limitations, an observer-based adaptive backstepping torque–position control approach is proposed in this paper. In order to achieve this objective, a novel external torque observer is proposed to alleviate the limitations associated with the use of force sensors. This paper’s main idea is to employ a three-channel architecture using a force sensor-less reflecting signal, which can improve transparency and increase algorithm performance. Furthermore, the another point of this paper is to enhance the safeness of operations in the presence of time-varying delays in the communication channel, a position error constraint control strategy is employed in the core of the proposed approach. Moreover, the primary advantage of this paper is that, the proposed observer-based control algorithm is relieved from the joints acceleration measurement of the leader and follower manipulators which is difficult in robotic systems. Finally, the stability analysis of the controller and observer together is conducted by the Barrier Lyapunov functional and series of simulations, comparisons and practical experiments are performed to validate the performance of the proposed algorithm.