Design And Rotor Displacement Self-sensing Technology Of Inverter Driven Six-pole Radial Hybrid Magnetic Bearing

A magnetic bearing is a type of bearing that generates electromagnetic force through permanent magnets or excitation coils,and the rotor is suspended in space stably,which avoids mechanical contact between the stator and rotor.The magnetic bearing has the advantages of no friction,no wear,no lubrication,high speed,high precision and long service life,and can be widely used in energy transportation,life science,aerospace,industrial production,wind power generation and other fields.In order to solve the problems of high cost and large power consumption of drive circuit for the four-pole and eight-pole magnetic bearings,the inverter driven three-pole magnetic bearing is studied.Then the inverter driven six-pole hybrid magnetic bearing(HMB)is proposed in this dissertation to improve the space utilization rate of the three-pole magnetic bearing,and the theoretical and experimental researches of its mathematical model and rotor displacement self-sensing technology are carried out.The main work and scientific research achievements of the dissertation are as follows:(1)The current research status of magnetic bearings is summarized based on the time sequence,the magnetic bearings are classified according to the classification criteria of magnetic bearing structure and working principle,and the characteristics of various magnetic bearings are analyzed.Then the research status,advantages and disadvantages of magnetic bearing rotor displacement self-sensing technology are summarized.(2)Based on the design requirement of the bearing capacity,the structure parameters of the six-pole radial HMB are designed,and the 3D model is built using finite element simulation software to verify the feasibility and correctness of the designed structure parameters.Since the six-pole radial HMB is an AC magnetic bearing,which is similar to the working principle of a bearingless motor,the mathematical model of the six-pole radial HMB is established using the Maxwell tensor method,and the accuracy and versatility of the method are analyzed.(3)Traditional magnetic bearing systems often use eddy current sensors to detect rotor displacement,which will bring about problems such as large volume,high cost and low reliability.In order to solve these problems,the rotor displacement self-sensing technology using least squares support vector machine(LS-SVM)is proposed.A rotor displacement prediction model based on LS-SVM is established for six-pole radial HMB,and the performance parameters of the prediction model are optimized using the improved particle swarm optimization(PSO)algorithm.Then the simulation model is established in Matlab to verify the feasibility and accuracy of the rotor displacement prediction model.(4)The digital control system of inverter driven six-pole radial HMB is constructed,and the overall control block diagram of the digital control system is also introduced.The hardware circuits such as DSP module and power drive module are designed,and the design of software including main program and interrupt service subroutine are introduced.Finally,an experimental platform of an inverter driven six-pole radial HMB is built.On the basis of this experimental platform,the rotor floating experiment,the stable suspension experiment and the anti-interference experiment are carried out.The experiment results show that the inverter driven six-pole radial HMB system proposed in this dissertation has good suspension performance and anti-interference performance.