Motion controller design for a mecanum wheeled mobile manipulator

Abstract

Mobile manipulators extend the workspace of manipulators by mounting them on mobile platforms. The paper presents the design of a motion controller for a mobile manipulator. The mobile manipulator consists of a mobile platform driven by Mecanum wheels and a robotic arm with 6 degrees of freedom. A Mecanum wheeled platform provides 3 degrees of freedom in motion. Such a platform is usually driven by 4 or more Mecanum wheels, which are mounted in a fixed position at the platform. If a mobile platform is driven by more than 3 wheels, it builds an over-actuated and over-sensed driving system. The paper develops a compact and easy applicable kinematic model of over-actuated Mecanum wheeled mobile platforms that includes the kinematic motion constraints of the system. The kinematic model is described by a single Jacobi matrix, which is invertible and therefore can be used in the forward and inverse kinematic model. Furthermore the paper describes the overall controller structure for our mobile manipulator OmnMan including the real-time synchronization of platform and manipulator. The motion controller of the platform includes a coupling controller that controls the kinematic motion constraints. Experimental results evaluates the effectiveness of the coupling controller.