Study On Control Strategy Of Bearingless Motors

According to the similar structure between the electromagnetic bearing and the AC motor's stator and rotor, the bearingless motor embedded the windings which are used to produce suspension force on the electromagnetic bearing into the motor's stator. These two windings will creat a special magnetic field. By changing and controlling this special magnetic field's distribution and speed purposefully,we can make rotor rotate and be suspended simultaneously.Because of the bearingless motor's potential value and complex operation control, the research on it has become a focus in the domain of the AC drive with high and ultra high speed in recent years.In this dissertation, the mathematical models of the bearingless induction motor are derived based on the anlysis of its basic principle. The study above lays the theoretical foundation on its suspension operation control.In order to simplify the system and improve the motor's perating performance two kinds of modified vector control strategy including motor winding modified air-gap flux orientation and motor winding modified rotor flux orientation for the bearingless induction motor are proposed. The two controlling system models are established in MATLAB/SIMULINK and comparative simulations are made under a wide range of operation conditions. The validity of proposed modified flux orientation strategy is proved by simulation results.In this desseration,a suspension winding air-gap flux cosed-loop control method based on DRNN network is proposed. Simulation results show that the proposed solution method can significantly improve the performance of the rotor suspension.At last,because of the inherent limitation of the mechanical displacement sensor,using the mechanical displacement sensor to detect the information of the rotor would severely limit the speed of the bearingless motor. According to the characteristics that the mutual flux component of suspension windings contains rotor radial displacement information, a rotor radial displacement estimation scheme using the mutual flux component of suspension windings was proposed in this paper, it found that it is able to achieve stable sensorless suspension operation.