Cooperative Strategy for Multiple Position-Controlled Mobile Robots

Abstract

This paper proposes a simple strategy for carrying a large object by cooperation of multiple position-controlled mobile robots on uneven ground. In cooperative systems handling single object, compliance is necessary for each robot to avoid excessive inner forces caused by the mutual positioning errors. The compliance is usually achieved by servo systems, but, the mutual positioning errors of robots often become uncontrollable due to the unevenness of the ground or the nonholonomic constraints of wheeled mechanisms. Thus, mechanical compliance is essential for cooperation of mobile robots on uneven ground. In this research, compliant mechanisms consisting of free joints are installed to a cooperative system. First, the mechanical compliance needed for the cooperation of position-controlled mobile robots is shown. As the theoretical results, it is revealed that the maximum number of robots which can directly support single object is six. Second, the statics and error characteristics of cooperative systems including compliant mechanisms are analyzed. An example for the cooperation of three mobile robots is designed using free joint mechanisms. Finally, the strategy is extended to cooperation among arbitrary number of mobile robots by building hierarchical structures with free joints.