Online Dynamic Tip-Over Avoidance for a Wheeled Mobile Manipulator With an Improved Tip-Over Moment Stability Criterion

Tipping over avoidance is critical for the success of mobile manipulation, especially in the cases that the onboard manipulators or the mobile vehicles move rapidly. Due to strong dynamics coupling between the onboard manipulator and mobile vehicle, online evaluation of dynamic stability of mobile manipulators and generation of strategies for tip-over avoidance still remain challenging. This paper presents an improvement tip-over moment stability criterion dealing with wheel-terrain and vehicle-manipulator interaction and proposes a real-time tip-over avoidance algorithm to minimize the tip-over moment transfer through either adjusting the posture of the onboard manipulators or changing the running velocity of the vehicle. The simulations and experiments on a four-wheeled mobile manipulator validate the correctness and feasibility of the proposed method.