Hybrid control of a two-arm robot for complex tasks

Abstract

For many coordinated tasks, a two-arm robot cannot be properly controlled by using a simple position control scheme and therefore requires a certain form hybrid control. Uchiyama and Dauchez recently proposed a symmetric hybrid position/force scheme for the manipulation of rigid objects rigidly held. The main results of this theory are summarized in this paper, and the limitations are pointed out. Several examples in which the relative motion of the end effectors cannot be neglected are presented: manipulation of rigid objects non-rigidly held, deformation of a flexible object, and assemblies of two objects “in space”. These tasks are analyzed and attempted control schemes are given for each of them. The dynamic effects are always neglected in this preliminary theoretical approach. An experimental setup built around two six axis PUMA arms and a parallel processing controller has been installed in order to validate our theoretical results. The hardware and software of this setup are also briefly described in this paper.