Improving the dynamic accuracy of industrial robots by trajectory pre-compensation

This paper presents a method to improve the path tracking accuracy of an industrial robot without replacing the standard industrial controller. By calculating off-line an appropriate trajectory pre-compensation, the effects of the nonlinear dynamics are compensated. This is realized by filtering the desired trajectory with the inverse dynamic model of the robot and its velocity controller. This compensation is applied as a velocity feedforward in the standard industrial controller avoiding the need for a torque control interface. The method presented is validated experimentally on a KUKA IR 361 industrial robot. The results show clearly an improved path tracking accuracy on circular trajectories.