Achieving a cooperative behavior in a dual-arm robot system via a modular control structure

In this paper the problem of achieving a cooperative behavior in a dual-arm robot system is addressed. A control strategy is conceived in which one robot is position controlled and devoted to task execution, whereas a suitable compliance is conferred to the end effector of the other robot to cope with unavoidable misalignment between the two arms and task planning inaccuracies. A modular control structure is adopted that allows the selection of the proper operating mode for each robot, depending on the task requirements. The proposed approach is experimentally tested in two different tasks involving the two robots in the laboratory setup. First, a parts-mating task of peg-in-hole type is executed; the robot carrying the peg is position controlled, whereas the robot holding the hollow part is controlled to behave as a mechanical impedance. Then, a pressure-forming task is executed, in which a disk-shaped tool is required to align with a flat surface while exerting a desired pressure; in this case, the robot carrying the disk is position controlled, whereas the robot holding the surface is force controlled. (C) 2001 John Wiley & Sons, Inc.