Cooperative Control System for Three Industrial Robots (Singular Configurations of Passive Joint Mechanisms)

Abstract

We propose a strategy for handling a large object by cooperation of multiple PID position-controlled manipulators and develop a cooperation system consisting of three commercial industrial robots. The developed system can handle a large object by cooperation of three robots. Three passive joint mechanisms consisting of four passive joints with electro-magnetic brakes are installed at the tip of each robot to avoid excessive inner forces due to mutual positioning errors. Since the geometrical relationships among three installed mechanisms and their joint angles must satisfy necessary kinematic conditions to avoid excessive inner forces, a simple way to check whether the necessary condition is satisfied or not is proposed. In order to investigate the effectiveness of the proposed strategy from the practical point of view, some fundamental experiments are done by using the developed system. Three 6 d.o.f. robots (Mitsubishi RV-E 3-ST) are open loop controlled by just a position commands which are calculated through inverse kinematics based on a desired trajectory of a handled object. From the results of experiments, the proposed strategy is confirmed and its effectiveness is verified.