A hierarchical control scheme for coordinated motion of mobile manipulators

Mobile manipulators are becoming more widespread, with growing commercial and scientific interest in their use. The addition of a mobile base to a manipulator greatly extends the workspace of the manipulator, but introduces complex control problems involving coordination of base and manipulator motion while simultaneously ensuring platform stability and good manipulability during task execution. This paper describes a hierarchical control scheme for a mobile manipulator designed to maintain manipulability and stability performance metrics within specified thresholds during the execution of manipulation tasks. We demonstrate the effectiveness of our control scheme by applying it to control of a simulated nonholonomic base with a 6 degree-of-freedom manipulator. Our simulation results show that the controller successfully completes a manipulation task involving multiple end-effector targets, and maintains stability and manipulability to the desired thresholds throughout.