Unified model approach for planning and control of mobile manipulators

Abstract

The capability of mobile manipulation is a key to many robotic applications in construction, space, underwater, nuclear plant and home services. In this paper, a unified dynamic model for integrated mobile platform and on-board manipulator is developed. The mobile manipulator is considered as a redundant robot in the model. It provides a efficient and convenient framework to design a mobile manipulator controller as well as its action plans. Combing the event-based planning and control method with the nonlinear feedback technique, a task level action controller is designed. An online kinematic redundancy resolution scheme has also been developed. The system stability has been proven in the normal operation as well as in the case of appearance of unexpected obstacles. Furthermore, a robotic task involving both position and output force control of mobile manipulator can be easily planned. As a result, a task requires controlling force and position at the same direction can be accomplished. To the best of o ur knowledge, this paper reports the first theoretical result as well as successful experiment of controlling force and position in the same task direction. The proposed unified model approach has been implemented and tested on a mobile manipulator consisting of a Nomadic XR4000 and a Puma 560 robot arm. A cart pushing task is used to demonstrate the efficiency and effectiveness of the proposed approach.