Research On Control Strategy For Suspension System Of Bearingless Motor With Rectifier Circuit

Permanent magnet Bearingless motors hold some advantages such as small volumefrictionless and higher efficiency. It has promising applications in the industrial field as lifescience, chemical engineering and semiconductor manufacturing. However, permanentmagnet has limited mechanical strength, and demagnetization under the situation of hightemperature. In order to take advantage of the merits and overcome the deficiencies ofpermanent magnet, a new type of beaingless motor with rectifier circuit is proposed. Theproposed bearingless motor structure is using a rotor with rectifier circuit coil to replacethe permanent magnet rotor, and it is supposed to work just like a bearingless permanentmagnet stepping motor. Therefore, the proposed bearingless motor will inherit all theperformances of permanent magnet motor. Additionally, the rotor has a better mechanicalstrength compared with permanent magnet motor, since the material of rotor is silicon steelsheet, and the reluctance can be decreased. Furthermore, it can overcome the deficiency ofdemagnetization. In this thesis, the structure and principle of bearingless motor with arectifier circuit was described. Based on the levitated operation of bearingless motor, ananalytical model was developed and the levitation control system of bearingless motor wasdesigned.Firstly, the background, development, applications and research trend of bearinglessmotor have been introduced in the thesis. The beraringless motor with rectifier circuit hasproposed based on studying the structure, control and testing technology of bearinglessmotor. The analysis shows the beraringless motor with rectifier circuit has advantages inhigh-temperature and high-speed conditions.Secondly, the structure, principle, levitation force and torque control ideas ofberaringless motor with rectifier circuit have been described. A relatively accurate modelof the motor has been proposed base on analysis of the electromagnetic field and maxwelltheory. The traditional PID control is limited by the contradiction between rapidity andovershoot, and the control system in actual industrial production has deficiencies as nonlinearity and time-variant. In order to overcome the deficiencies of PID controller, theauto-disturbances-rejection control theory is used to design the suspension control systemof the bearingless motor. According to prototype parameters, simulation model was set upwith MATLAB/SIMULINK platform to analyze performance of the system. Thesimulation experiment shows that the active disturbance rejection control for suspensionsystem has the features of high precision, small overshoot, fast convergence rate and stronganti-jamming, meeting the high performance control requirements for the bearinglessmotor suspension system as stable and accurate positioning.Finally, in order to obtain radial position of rotor for the beraringless motor withrectifier circuit. The measurement system, installation scheme, radial and axial couplingerrors has been analyzed in the thesis for the beraringless motor with rectifier circuit.