Dynamic stiffness enhancement of direct-driven machine tools using sliding mode control with disturbance recovery

This paper presents a disturbance adaptive discrete sliding mode controller for feed drives equipped with linear motors. The control law is expressed as a function of friction and cutting force disturbances which are estimated from the motor force and control states. The accurate prediction of disturbance forces is used to actively compensate low frequency machine tool structural modes which are within the bandwidth of the controller. The proposed control system is experimentally demonstrated on a high performance linear drive, which exhibited high bandwidth and significant increase in dynamic stiffness compared to classical cascaded control methods. (C) 2009 CIRP.