Stability evaluation for mobile manipulators using criteria based on reaction

This research is concerned with a stability control method with a criterion based on reaction for motion control of a mobile manipulator. Mobile manipulators can propel themselves around a work area and can operate over a wide area. Then, a stability evaluation and a stability control method must be required for mobile manipulators that are not fixed on a floor. The evaluation method based on ZMP (Zero Moment Point) criterion, in which the model is regarded as a particle system, is not satisfactory for evaluating stability of a mobile manipulator that consists of solid links. In addition, transient state during tipping over has not been discussed. In this paper, we propose a stability evaluation criterion based on reaction for the solid model of a dynamic mobile manipulator. First, equations of motion of the mobile manipulator for stable and unstable states of motion are formulated based on constraint conditions. Second, a stability criterion based on reaction is proposed by referring the formulated model. Third, the relationships between changes in reaction and changes in ZMP during tipping over are discussed through simulations. Finally, it is shown that a mobile manipulator can return from unstable transient state to stable state by performing stability compensation motion.