Flow-limited path-following control of a double Ackermann steered hydraulic mobile manipulator

Abstract

This paper presents an approach to realize tool path-following control of double Ackermann steered wheeled mobile manipulators. Path-following is achieved by time scaling of motion trajectories when the vehicle-manipulator becomes subject to actuator flow bounds and/or tracking errors arising from limitations of the hydraulic actuation system. Our strategy combines 1) a platform path-following controller with explicit velocity bounds calculated from the a priori known pump flow limits, and 2) a manipulator trajectory scaling method based solely on the monitored position tracking error. The proposed method effectively allows the manipulator to readjust its position when facing unexpected disturbances, by propagating the scaling factor based instantaneous tool center point position errors to the platform path-following controller, to yield coordinated advancement on a predefined path. Simulation results are provided to verify the effectiveness of the method.