Dynamics of the Five-Bar-Link Parallel Direct-Drive Robot Manipulator

Abstract

A direct-drive motor is an attractive actuator for a robot manipulator because of its high driving torque and accurate positioning abilities. The motion of a robot manipulator driven by a direct-drive motor is, however, strongly affected by inertial forces and nonlinear forces such as coliolis and centrifugal forces because it does not have any transmission mechanisms. It is, therefore, necessary to dynamically control the torque of the direct-drive motors in order to attain accurate motion of the robot manipulator. In this paper, the dynamics of a five-bar-link parallel direct-drive robot manipulator are analyzed. The torque control curves of the direct-drive motors for a three dimensional robot manipulator are derived. A new feedback method (learning control) is adopted, and the effects of the learning control on the motion of the direct-drive robot manipulator are investigated. The robot manipulator must be effective for machining and assembly when the torque is controlled with high accuracy.