Enhancement of Force Exertion Capability of a Mobile Manipulator by Kinematic Reconfiguration

With the increasing applications of wheeled mobile manipulators (WMMs), new challenges have arisen in terms of executing high-force tasks while maintaining precise trajectory tracking. A WMM, which consists of a manipulator mounted on a mobile base, is often a kinematically redundant robot. The existing WMM configuration optimization methods for redundant WMMs are conducted in the null-space of the entire system. Such methods do not consider the differences between the mobile base and the manipulator, such as their different kinematics, dynamics, or operating conditions. This may inevitably reduce the force exertion capability and degrade the tracking precision of the WMM. To enhance the force exertion capability of a WMM, this letter maximizes the directional manipulability (DM) of the manipulator, with consideration of the joint torque differences, first in Cartesian space and then in the null-space of the robotic system. To maintain precise end-effector trajectory tracking, this letter proposes a novel coordination method between the mobile base and the manipulator via a weighting matrix. The advantages and effectiveness of the proposed approach are demonstrated through experiments.