Design, modeling and control of a hybrid machine system

A hybrid machine is such a machine where its drive system integrates two types of motors: the servomotor and the constant velocity (CV) motor. The existing research on the hybrid machine prototypes usually uses two servomotors, of which one mimic the CV motor by prescribing a constant velocity trajectory profile. It is obvious that this departs away from the real situation where a CV motor is in place. The CV motor will bring in the velocity fluctuation which can not be attenuated by the CV motor itself due to the lack of a control mechanism in the CV motor, yet be propagated to the servomotor, and further to the end-effector of the machine. The general strategy for controlling the hybrid machine is therefore to model this propagated fluctuation and incorporate it into a controller for the servomotor. A controller based on the sliding mode control technique is proposed for the hybrid machine in this paper. The stability analysis shows that the controller is asymptotically stable. Simulation with a preliminary test demonstrates the effectiveness and robustness of this controller. Finally, we examine further performance improvement through attaching a flywheel on the CV motor to demonstrate the effectiveness of the synergy of the integration of mechanical and electrical means. (C) 2004 Elsevier Ltd. All rights reserved.