Robust stability for bilateral teleoperation systems under time-varying delay by communication disturbance observer

In time-delayed systems in which the time delay is unknown and unpredictable, to guarantee the stability of the system, a compensation method should be used. In this paper, this method is based on the concept of network disturbance and communication disturbance observer (CDOB), which does not need the time delay model. Therefore, it can be implemented in teleoperation systems that contain communication channel with time-varying delay. However, it has been observed that the system model error seriously affects the steady-state characteristics and causes steady-state error. Also, applying disturbance to the system makes it unstable. Therefore, in this paper, by using slave's delayed torque instead of its delayed position, the structure of the conventional CDOB is changed and another structure for CDOB is proposed to achieve robustness against disturbance and model uncertainty. Also, steady-state characteristics and disturbance attenuation characteristic of the structure are studied. Simulation results are presented to demonstrate the effectiveness of the proposed structure.