Research On Model Predictive Current Control Of A Bearingless Induction Motor

A bearingless induction motor(BL-IM)combines the functions and advantages of the magnetic bearings and the induction motors.The BL-IM has the advantages of simple structure,no friction loss,long service life and so on.It is used in many special electrical field,such as high-speed precision machining,turbo molecular pump,flywheel battery,aerospace,aseptic workshops,vacuum technology,life sciences and so on.And it has shown extremely important application value.The research in this dissertation was carried out on the BL-IM operating principles,mathematical models,model predictive current control(MPCC)in the suspension part,MPCC in the torque part and implementation of the digital control system.The main work and achievements are as follows.Firstly,the research background,the application fields and the development trend of the BL-IM are reviewed,and the research summary and the development trend of the MPCC technology are described.According to the working principle of the BL-IM,the mathematical model is derived,and the BL-IM air gap field oriented control system is built.The simulation results show that the motor under this strategy can suspend and rotate stably,and lays the foundation for the subsequent MPCC research.Secondly,to solve the problem of the poor anti-interference of the suspension winding current in the traditional BL-IM direct suspension force control process,a MPCC strategy based on the direct suspension force control is proposed in the suspension part of the motor.The MPCC is introduced into the traditional BL-IM direct suspension force control system,and a sliding mode flux linkage observer is designed to directly use the observed stator flux linkage in the MPCC system.The simulation results show that this strategy improves the suspension performance and antiinterference performance of the BL-IM.Thirdly,to solve the problem of the untargeted optimal allocation of the current components on the d and q-axis of the BL-IM torque winding by the objective function in the traditional MPCC process,a MPCC strategy based on the fuzzy dynamic objective function is proposed in the torque part of the motor.The weight factors are introduced into the traditional objective function,and the influence of the BL-IM under different weight factors is analyzed.The fuzzy dynamic objective function is designed,the fuzzy universe is established and the fuzzy inference is performed.The simulation results show that this strategy improves the speed characteristics,current characteristics and the suspension performance of the BL-IM.Finally,the software and hardware control system with TMS320F2812 DSP chip as the core chip of BL-IM digital control system are constructed.The BL-IM speed,current,rotor radial displacement and rotor trajectory experiments are carried out based on the experimental platform of the research group,the experimental waveforms are given and analyzed.The results show that the digital control system can realize the stable suspension and rotation of the BL-IM,and it has excellent static and dynamic performance.