Control Aspects Of Steel Plate Magnetic Levitation System

Steel plate magnetic levitation systems provide such a way of supporting steel plate without any contact that make contactless conveyance possible, which will open up various sphere of application. Much attention have been paid to the magnetic suspension control technology which is considered as one of the key part in the entire magnetic levitation system, due to the fact that magnetic levitation system is inherently unstable. The research work of this dissertation is carried out on the basis of a 4-magnet supported steel plate magnetic suspension system prototype, and the main research aspects are listed as follows:(1) Research on acceleration feedback control to improve suspension quality of magnetic levitation system.In order to improve the anti-disturbance ability of steel plate magnetic levitation system, measured acceleration signal is used to realize acceleration feedback control. The traditional acceleration feedback control strategy used for rigid object is extended to the case considering resonance effect, and related theoretical analysis and experimental research on acceleration control is carried out.Firstly, to overcome the constraint in implementation of acceleration control due to resonant effect, a model of suspension system considering resonant effect is derived and its influence on closed loop stability is analyzed. A control strategy that employs an acceleration notch filter to attenuate vibration is proposed. Secondly, in order to fast and accurately measure the resonance frequency, and simplify the implementation of the notch filter, an adaptive notch filter is adopted to identify the resonant frequency and realize the function of the notch filter. Finally, the method for performance index selection and the way to optimize controller parameters is discussed. Experiments are carried out to verify the validity of acceleration feedback control based on the prototype.(2) Research on cross-coupled control for gap synchronization of multi-magnet supported magnetic levitation system.Conventional cross-coupled control is extended to multi-magnet supported magnetic levitation system. Corresponding theoretical and experimental research are developed to implement gap synchronization control of magnetic levitation system in order to eliminate effects on gap due to gain parameter, dynamic parameter mismatch between each single magnet suspension system and uncertain disturbances while steel plate is levitated, to improve gap dynamic synchronization performance.Firstly, research starts on the basis of one 2-magnet supported magnetic levitation system to seek appropriate cross-coupled control strategy suitable for magnetic suspension system so as to provide theoretical basis for 4-magnet supported magnetic levitation system. Drawbacks of applying traditional cross-coupled control to 2-magnet supported magnetic levitation system is pointed out and then one improved cross-coupled control strategy is proposed by introducing both gap and velocity cross-coupled terms to realize gap synchronization control.Secondly, conventional cross-coupled control is oriented for double-axis system so that synchronization error can be simply chosen as the output difference between those two axes. However, for multi-axis system, there are many ways to select synchronization error and different selection ways have different influence on the coordinated performance of each axis. So, it is vital to seek appropriate way to construct synchronization error to implement cross-coupled control. Several applicable methods are compared and one of the most suitable ways is determined to utilize in the magnetic levitation system.Thirdly, while the cross-coupled control law and synchronization error selection is derived, the scope of implementation synchronization coordinated control should be determined. Theoretical research concerning local and global synchronized coordinated control strategy is carried out respectively to obtain optimized coordination of multi-magnet systems. Experiments are carried out on the prototype of steel plate magnetic levitation system and experimental results show the effectiveness of the proposed control method.