Robot trajectory generation for three-dimensional flexible load transfer

Abstract

This paper addresses the problem of reducing the elastic deformations and the residual vibrations of flexible loads when they are handled by a robot manipulator. During the manipulation of the low-stiffness load, such as bumper or exhaust system in automotive industry, large motion-induced deformations and vibrations may be induced. These deformations will have detrimental effects on the settling time, on the accuracy and on the integrity of the operational process in a constrained environment. The trajectory shaping approaches, i.e smoothing filter or input shaping method are well-known solutions for the suppression of the residual vibrations at the end of a rest-to-rest motion. However, using trajectory shaping technique alone may not be sufficient to suppress the static elastic deformations during the transfer phase of the object. Thus, the main contribution of this paper is to propose a two stages feedforward based approach that combines trajectory shaping technique for vibrations reduction, with a deformation compensation trajectory. The latter exploits the rotation space of the manipulator to mitigate the flexural motion of the flexible load. The effectiveness of the proposed method is demonstrated by experimental validations on an industrial robot Kuka iiwa.