Control of Manipulators With Flexible Joints and Links by Non Linear Inversion, Modal Damping and Joints Stiffening

Abstract

This paper deals with the control problem of a manipulator with flexible links and joints. First, we use a non linear based approach to control the rigid global motions of the robot with rigid joints and flexible links. This non linear feedback is coupled with an external loop which damps the elastic motions considered as pertubations of the rigid nominal ones. Second, we decide to control the torques after the joint springs in order that they track the control torques provided by the first control layer. This is achieved via an additional non linear feedback superimposed with fast local torque controllers. In fact such a strategy consists of damping the first distributed mode of the robot and stiffening the joint flexibilities. Such a solution seems to be a good compromise between energy consumption and simplicity of the controller.