High speed precise control of robot arms with assigned speed under torque constraint by trajectory generation in joint co-ordinates

This paper presents a methodology for off-line trajectory generation that guarantees high-speed and precise end-effector point-to-point (positioning) control of industrial robot arms, within the bounds of the most relevant constraints. The constraints being addressed are the saturation of joint torque and the limit of Cartesian velocity. In the proposed methodology, shortest path of travel and maximum-joint torque/acceleration utility is guaranteed so that the true minimum-time trajectory is generated. The minimum-time trajectory is then compensated for the delay dynamics using a feedforward compensator. An illustrative implementation is presented using the Performer MK-3s robot arm, with which attractive results have been obtained. Being an off-line algorithm, the proposed method can be conveniently introduced into existing servo control systems of industrial robot arms, and to enhance their performance.