Robust control of mobile manipulators

Abstract

A mobile manipulator is basically a manipulator mounted on a mobile vehicle. This arrangement has some advantages over stationary robots and mobile robots, such as the infinite workspace and the ability to avoid singularities. However, the control problem becomes a sophisticated one. This is due to the nonlinear and nonholonomic constraints governing the motion of the vehicle. Moreover, the dynamics of the manipulator and the vehicle are highly coupled; ground-surface irregularities, for example, affect the motion of the end effector kinematically and dynamically. A mobile manipulator is expected to pass through different environmental conditions, a fact which calls for a robust control scheme. Unfortunately, the robust control problem for nonholonomic systems is not well defined yet. Since the ultimate goal of control is to control the motion of the manipulator's end effector, it is proposed in this article to tackle the robustness issue by designing a manipulator decoupling controller. This controller aims at rejecting disturbances arising from the motion of the vehicle. © 1996 John Wiley & Sons, Inc.