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 ro bot is position controlled and devoted to task execution, whereas a suitabl e compliance is conferred to the end effector of the other robot to cope wi th unavoidable misalignment between the two arms and task planning inaccura cies. A modular control structure is adopted that allows the selection of t he proper operating mode for each robot, depending on the task requirements . The proposed approach is experimentally tested in two different tasks inv olving the two robots in the laboratory setup. First, a parts-mating task o f peg-in-hole type is executed; the robot carrying the peg is position cont rolled, whereas the robot holding the hollow part is controlled to behave a s a mechanical impedance. Then, a pressure-forming task is executed, in whi ch a disk-shaped tool is required to align with a flat surface while exerti ng a desired pressure; in this case, the robot carrying the disk is positio n controlled, whereas the robot holding the surface is force controlled. (C ) 2001 John Wiley & Sons, Inc.