Theory and application of a combined feedback–feedforward control and disturbance observer in linear motor drive wire-EDM machines

• Published in: International journal of machine tools & manufacture Vol. 48; no. 3; pp. 388 - 401
• Main Authors: Yan, Mu-Tian, Shiu, Yau-Jung
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.03.2008; Elsevier
• Subjects: A.c. Machines; Applied sciences; Computer science; control theory; systems; Control system synthesis; Control theory. Systems; D.c. Machines; Disturbance observer; Electrical engineering. Electrical power engineering; Electrical machines; Exact sciences and technology; Feedforward controller; Mechanical engineering. Machine design; Motion control; Permanent-magnet linear synchronous motors; Disturbance observer; Feedforward controller; Permanent-magnet linear synchronous motors; Motion control; Disturbance rejection; Tracking; High precision; Feedback regulation; Control synthesis; Modeling; Pole assignment; Synchronous motor; Direct drive; Tracking error; Linear motor; Robustness; Electric motor; Feedforward; Dc motor; System with two degrees of freedom; Magnetic hysteresis; Experimental study; Electrical discharge machining; Friction; Tracking(movable target); Drive mechanism; Permanent magnet; Non linear effect; Differential integral proportional control
• ISSN: 0890-6955; 1879-2170
• DOI: 10.1016/j.ijmachtools.2007.09.006

This paper presents a combined two-degree-of-freedom controller and disturbance observer design for a direct drive motion control system actuated by permanent-magnet linear synchronous motors (PMLSM). A feedback controller based on pole-placement design method is proposed to achieve desired tracking performance as well as stabilize the closed-loop system. A newly designed feedforward controller is proposed to reduce tracking errors based on an inverse model of the direct drive system. A digital disturbance observer is implemented to be included in the proposed feedback–feedforward control structure to compensate for nonlinear friction, cogging effects, and external load disturbance. Furthermore, the proposed control scheme has been verified as being internally stable. Experimental results indicate that the proposed controller can achieve a high contouring accuracy of ±0.3 μm as well as provide disturbance rejection and robustness. The maximum contour error of circular trajectory was reduced from 8.5 to 3.2 μm in comparison with proportional-integral-derivative (PID) controller.