Performance-functional based controller design for a mobile manipulator

Mobile manipulators with more than 6 degrees of freedom (DOF) provide a large working space with high end effector dynamics. The paper shows how mobile manipulators consisting of a normal robot arm on a wheeled mobile base can be controlled. The coordination of movements of the robot and the base is determined by using a direct task-space control. The task vector is augmented by the redundant DOF´s of the base, so that the external and internal motions of the manipulator can be determined by means of optimal control theory. The reference values of the augmented coordinates are derived from the end effector references. This is done by optimizing robot arm kinematics under the dynamic conditions of the base. Furthermore, it is shown how not task-determined end effector DOF´s can be used to improve the dynamic characteristics of the remaining DOF´s. As an example, the proposed controller design is used to coordinate the movements of a mobile manipulator with nine DOF´s and nonholonomic constraints