A unified approach to motion control of mobile manipulators

This paper presents a simple on-line approach for motion control of mobile manipulators comprising a manipulator arm mounted on a mobile base. The proposed approach is equally applicable to nonholonomic mobile robots such as rover-mounted manipulators and holonomic mobile robots such as tracked robots and compound manipulators. For wheeled mobile robots, the nonholonomic base constraints are incorporated directly into the task formulation as kinematic constraints. The configuration control approach is extended to exploit the redundancy introduced by the base mobility to perform a set of user-specified additional tasks during the end-effector motion while satisfying the nonholonomic base constraints (if applicable). This approach treats the base nonholonomy and the kinematic redundancy in a unified manner to formulate new task constraints. The computational efficiency of the proposed control scheme makes it particularly suitable for real-time implementation. Two simulation studies are presented to demonstrate the applications of the motion control scheme to a rover-mounted arm (nonholonomic system) and to a tracked robot (holonomic system).