Impedance control of mobile manipulator with the stability to external force

A method of the impedance control of a mobile manipulator with the stability to the external force acting on the workpiece is proposed. (1) It is assumed that the robot does not know the workpiece´s desired trajectory and is commanded directly by the external force. (2) Different types of desired impedance are set to the workpiece and the vehicle; the workpiece behaves as a desired mass to the external force, and the vehicle responds to the input of its desired position as a typical linear second-order system. Thus, the manipulator responds to the fast change in the force and the vehicle responds to the slow change. (3) For the purpose of keeping the robot stable-preventing it from tumbling-to the external force, the vehicle´s desired position is determined so that the robot´s zero moment point may come nearest to the center of the supporting polygon. Accordingly, the vehicle moves toward the most stable position