An Industrial-Robots Suited Input Shaping Control Scheme

Abstract

Compliance in robot mounted force/torque sensors is useful for soft mating of parts in many assembly tasks. Nevertheless, it generates nearly undamped oscillations when moving a heavy end-effector in free space. In this paper, input shaping control is investigated to damp such unwanted flexible modes. However, the conventional method presents a major drawback: To eliminate the oscillatory dynamics, the desired motion profiles have to be shaped and thus modified. This means that although the unwanted vibrations are damped, the robot motion does not meet the desired one. In this paper we first review the conventional input shaping technique. Second we show how the mentioned problem may be fixed in the design phase by discretizing the filter and by using a predictive approach that compensates the shaped signals time delay and minimizes the resulting control error. Simulation results are presented.