H∞ 2DOF control for the motion of a magnetic suspension positioning stage driven by inverter-fed linear motor

• Published in: Mechatronics (Oxford) 2003-09, Vol.13 (7), p.677-696
• Main Authors: Kang, B.J., Hung, L.S., Kuo, S.K., Lin, S.C., Liaw, C.M.
• Format: Article
• Language: English
• Subjects: Applied sciences; Bearings, bushings, rolling bearings; Computer science; control theory; systems; Control system synthesis; Control theory. Systems; Drives; Exact sciences and technology; H∞ control; Inverter-fed linear motor; Magnetic suspension; Mechanical engineering. Machine design; Model following control; Positioning stage; Precision engineering, watch making; Two-degrees-of-freedom
• ISSN: 0957-4158; 1873-4006
• DOI: 10.1016/S0957-4158(02)00037-5

To achieve robust linear position driving control with contactless and low mechanical friction, this paper presents the development of a magnetic suspension positioning stage directly driven by an inverter-fed linear permanent magnet synchronous motor (LPMSM). First, an experimental linear positioning system is established. In which, the LPMSM is fed by a properly designed current-controlled inverter having accurate and quick current tracking response, and the magnetic suspended supporting mechanism is employed. In addition, to enhance the driving control performance, the laser position sensing system and personal computer-based controller are also properly set up. The dynamic model of the whole drive system is estimated from the measurements. And accordingly, a two-degrees-of-freedom control scheme consisting of a command feedforward controller and an H ∞ feedback controller is designed firstly to fulfill the specified positioning control requirements at nominal case. Then, a simple model following controller is further added to preserve the desired control performance as the operating condition and parameter changes occur. Some simulated and experimental results reveal that quantitative and robust position control performances are obtained by the proposed controller.