Stability compensation of a mobile manipulator by manipulator motion: feasibility and planning

In order for a mobile manipulator to move stably (without overturning) and execute end-effector tasks simultaneously, a manipulator with redundancy is effective. Using this redundancy, it is possible to perform tasks at an expected manipulator configuration when the robot is stable and compensate system stability when the robot is unstable. However, the ability to compensate stability by this manipulator motion is limited. Thus, in order to ensure the feasibility of stability compensation, the task plan or vehicle motion must be within this ability. In this paper, first the concept of the stability compensation range by static posture change is proposed. Then, within the stability compensation range, the compensation motion of a redundant manipulator considering an expected manipulator configuration and the system stability is derived, given the end-effector trajectory and the vehicle motion. Finally, the effectiveness of this method is illustrated by simulation examples.