Design of mechanisms for cooperation among multiple position-controlled robots

This paper proposes a strategy for handling a single object by cooperation of multiple robots controlled by PID position controllers. Since such a cooperative system has mechanical closed loops, installation of free joints or flexibility among robots is necessary to avoid excessive inner forces caused by the positioning error of each robot. First, the essential kinematic conditions to achieve the cooperation among position-controlled robots are shown. Second, the relationship between the positioning error of the handling object and that of each robot is analyzed. Finally, a mechanism for the cooperation of three mobile robots is proposed and its kinematic characteristics and statics are analyzed. The strategy proposed here is very effective and practical for cooperation of not only conventional industrial robots but also distributed autonomous mobile robot systems with non-holonomic constraints