Direct Control Of Bearingless Permanent Magnet Slice Motor Based On Prediction Model

The emergency of the bearingless permanent magnet slice motor(BPMSM)is an important milestone in the history of bearingless motor.The BPMSM is a novel high-performance special motor,which not only preserves the characteristics of high power factor,small torque ripple of the permanent magnet synchronous motor,but also inherits the advantages of the bearingless motor like high speed,high precision,no friction,no abrasion,long service life and so on.In addition,aiming at the defects of the traditional bearingless motor,such as complex mechanical structure and difficult system control,the passive suspension of the motor on three degrees of freedom in axial direction and torsion is successfully realized by adopting a special thin slice rotor structure.Only the remaining two degrees of freedom are realized suspension by active control.Compared with the traditional bearingless motor,the control difficulty and manufacturing cost are greatly reduced.At the same time,due to the compact structure,it can be used as the driving core of the pump to realize the non-pollution transfer of liquid,which has broad application prospects in special transmission fields where require high precision and cleanliness,such as biomedicine,semiconductor industry,aerospace and so on.The dissertation is supported by Key Research and Development Program of Jiangsu Province(BE2016150)and Jiangsu Province “Qinglan Project”.In this dissertation,the 2/4 pole surface mount permanent magnet sheet motor of our laboratory is taken as the research object and the main research focus is on its basic theory and control strategy.The main contents and achievements are as follows::Firstly,the general situation of the development of bearingless technology in the field of motor is summarized systematically in this dissertation,including the research background and significance,industrial application prospect,future development trend,and the key control strategies and so on.Secondly,the structure of the BPMSM and the suspension principle are analyzed,then mathematical models of active and passive suspension systems are deduced.Aiming at the weak points of the traditional voltage-current model in the estimation offlux linkage,a new flux linkage observer is designed,and its structure,observation principle and realization algorithm are illustrated in detail.The flux observation model is derived by the small signal analysis method.Finally,a double closed-loop control system of radial displacement and suspension force is constructed according to the designed flux linkage observer.The model is built in Matlab to verify the correctness and reliability of the control strategy.Thirdly,due to the problem of signal sampling delay in digital control,in this dissertation,the idea of predictive control is incorporated into the direct control method to compensate the closed-loop feedback value of the system.According to the control strategy,the BPMSM system is divided into two parts: radial displacement closed loop and rotational speed closed loop.Based on the flux observer designed above,two subsystem predictive controllers for torque and suspension force are designed respectively,then the principle and algorithm are analyzed in detail,and the predictive models of torque and suspension force are deduced.Finally,the block diagram of the BPMSM predictive direct control system is designed,and the model is constructed in Matlab to verify the correctness and reliability of the control strategy.Finally,the digital control platform of the BPMSM is built,and the control modules of electromagnetic torque and radial suspension force are designed.According to the proposed scheme,the digital control system is debugged.In order to facilitate the control and real-time monitoring of the system,a communication interface based on Labview is designed,and then the experimental verification and analysis of the designed control system are carried out.