Stability Control for a Vehicle-Mounted Manipulator

Many future applications of robotic systems will require that manipulators perform operations while being carried by moving vehicles. However, different from a manipulator fixed on the floor, such a vehicle-mounted mobile manipulator might be unstable or even tip over. Previous work on stability control hardly considers dynamics and environmental disturbances. The stability of a mobile manipulator has a close relation with the vehicle's motion, the manipulator's posture and motion, and the endpoint's force. And it is necessary for a mobile manipulator to have proper stability when it is used for tasks in various environments with disturbances. This paper first discusses concepts about stability such as the stability degree and the valid stable region based on the ZMP (Zero Moment Point) criterion, which can be used as effective stability criteria in controlling a mobile manipulator. Then, as a control scheme for maintaining or recovering stability, the method of ZMP path planning by a stability potential field is presented. Based on the above-mentioned considerations, a motion planning algorithm is then formulated, which controls the manipulator in order to maintain the stability of the whole system while the vehicle is moving along a given trajectory. Finally, the effectiveness of the method is illustrated by computer simulation.