Control of nonlinear bilateral teleoperation systems subject to disturbances

Teleoperation systems, consisting of a pair of master and slave robots are subject to different types of disturbances such as joint frictions, varying contact points, unmodeled dynamics and unknown payloads. Such disturbances, when unaccounted for, cause poor teleoperation transparency and even instability. This paper presents a novel nonlinear bilateral control scheme, based on the concept of disturbance observer based control, to counter these disturbances and their negative effects on the teleoperation systems. The proposed disturbance observer based bilateral control law is able to achieve global asymptotic force tracking, and global exponential position and disturbance tracking in the presence of various disturbances. The minimum exponential convergence rate of the position and the disturbance tracking errors can be tuned by the controller parameters. Simulations are presented to show the effectiveness of the proposed control scheme.

I. Introduction

Every teleoperation system consists of a master robot and a slave robot. The master interacts with a human operator and the slave interacts with a remote environment. If force feedback from the slave side to the master side is provided, the system is called a bilateral teleoperation system to distinguish it from a unilateral teleoperation system. A bilateral teleoperation system is said to be transparent if the slave robot precisely follows the position of the master robot and the master robot faithfully displays the slave-environment contact force to the human operator.