Asymptotic Stable Guidance Control of PWS Mobile Manipulator and Dynamical Influence of Slipping Carrying Object to Stability

The research concerning mobile manipulator being composed of a mobile robot and a mounted manipulator has been growing a topic. Further, traveling operation that means the mounted manipulator operates during traveling can improve the efficiency, since it can prepare some tasks during traveling for desired tasks required to do at the destination place. The traveling operation is also important for active sensing by hand-eye camera equipped at the top link of the mounted manipulator, because the camera have to be directed temporally to the moving object in the camera image to obtain information for navigation. However, the traveling operation of the mobile manipulator involves some difficulties to control, such as dynamical interference and non-holonomic character. Therefore the trajectory-tracking errors of the mobile robot that means the base link of the mobile manipulator are integrated on the floor. This integration is caused by the non-holonomic constraint expressed by a differential equation of first order. As the result of it, the integrated error never converges to zero by a controller being used usually for fixed manipulator, since the controller is based on the holonomic character. Constructing a controller including a consideration of the non-holonomic constraint can solve this problem. In this paper, we propose a control method that guarantees zero convergence of guidance errors and the trajectory tracking errors of mounted manipulator, and the proof is given by Liapunov method. Simulations confirm the performances of the proposed controller, and the results show that the guidance errors and trajectory-tracking errors converge to zero. Furthermore the dynamical influences that slipping carrying objects give to the tracking controller are evaluated by the resulted trajectories on the floor.