Velocity control of mobile manipulators

When a serial-chain manipulator is mounted on a mobile base, the end-effector motion must be decomposed into the motion of the base and the motion of the manipulator. The determination of actuator rates for a given end-effector motion is typically underconstrained. By associating with each joint, a compliance function, local as well as global solutions for the inverse kinematics of kinematically redundant systems can be obtained. The rate decomposition problem is formulated using screw theory. Analytical expressions are obtained for the local solution for perfectly general systems, including those with nonholonomic constraints. Global integral solutions are also obtained using this framework. Nonholonomic systems require that additional constraints be imposed to remove the nonholonomy in the system. The basic goal of allocating the end-effector motion between the manipulator and its mobile base according to user-prescribed preferences is demonstrated using computer simulations and experiments