Cooperative strategy for multiple mobile manipulators

This paper proposes a simple method for carrying a large object by cooperation of multiple mobile manipulators with position controllers. It is necessary for each robot to have compliance in order to avoid excessive inner forces due to the mutual positioning errors. Thus manipulators on mobile platforms are used as free joint mechanisms by locking some joints and making the rest joints free. These free joints play the role of mechanical compliance. First, compliance needed for cooperation among position-controlled robots is shown. Second, the statics and error characteristics of cooperative systems including compliant mechanisms are analyzed. Some feedback control laws for platforms moving on rough ground are proposed and discussed.