Dynamic Compensability for Robot Manipulators Mounted on a Flexible Base

Abstract

This paper addresses issues of analysis and evaluation of manipulation characteristics for robot manipulators mounted on flexible base. End-effector motion of such the robot system can be divided into two parts: one is generated from the motion of the robot joint, another is resulted from the base flexural behavior. The latter, however, is always not desirable in the end-effector control, due to it appears as a trajectory tracking error. Such the tracking error has to be compensated by the joint torque of the manipulator in order to perform manipulation tasks precisely. It must be the case that the compensating is not possible when the robot takes some certain configurations, thus, clarifying the possibility and ability of such the compensating dynamically and manipulatively is strongly needed. From mapping relationships among accelerations of the joints, flexible base and end-effector, we introduce a concept of dynamic compensability of robot manipulators mounted on a flexible base. By analyzing the mapping relationships, some conditions are derived for judging dynamic compensability of the robot system. A dynamic compensability measure and dynamic compensability ellipsoid are proposed to evaluate degree of dynamic compensability. Calculation examples are carried out to illustrate utilization of the introduced concept.