Improving transparency in macro-micro tele-manipulation by means of external force estimation

The use of teleoperation systems has been increased for micromanipulation tasks in the last decade. The most applications are where the operator is physically limited due to micro dimensions. The most common control approaches for nonlinear systems i.e. Proportional Derivative (PD) controllers, have a considerable deficiency in the contact motion transparency. In this paper, a novel control strategy is proposed for the nonlinear bilateral macro-micro teleoperation system with the time delay. In addition to position and velocity signals, force signals are also utilized in the control scheme. This modification significantly improves the poor transparency in contact with the environment. To eliminate the external force measurement, a new modified force estimation algorithm is proposed for the master and slave robots. The closed loop stability of the nonlinear macro-micro teleoperation system with the proposed control scheme is investigated by the Lyapunov theory. The main achievement is the stability of closed loop macro-micro teleoperation system in presence of the time varying human and environment forces. In addition, perfect tracking and force reflection have been proved in the steady state condition at the same time. Experimental results verify the efficiency of the new control scheme in the free motion and when slave robot is in contact with the environment.