Suspension Force Model And Digital Control System For Bearingless Induction Motors

The bearingless motor, in which torque and suspension force independent control can be realized simultaneously, is a new type of motors. As one of the most important research directions on high-speed or super high-speed motors, it has aroused wide attention of experts and scholars all over the world. The bearingless induction motor, because of its simple structure, high reliability, air-gap uniform and easy field weaken, has more value of research and applications than other bearingless motors.The bearingless induction motor is a multi-variable, non-linear, strong-coupled complicated system. At the support of National Natural Science Foundation of China, the research of the dissertation focuses on the suspension force models and the digital control system, including the suspension force mathematic models, the rotor flux oriented controller, the rotor displacement detection and the design of digital control system of the bearingless induction motor. The detail contents are as follows:Firstly, the research background and the developing situation are summaried at home and abroad of bearingless motor, then the research status, the developing direction, the research significance and the latent using value of bearingless induction motor are expounded detailedly.Secondly, the principle of the bearingless induction motor is introduced, and the suspension force models based on the magnetic force and the inductance matrix are given, the correctness of suspension principle and suspension force models are verified by ANSYS software, which is finite element analysis software of electrical machines.Thirdly, in allusion to the coupling characteristics between the electromagnet torque and radial suspension forces of bearingless induction motor, the rotor flux oriented control strategy based on torque winding is investigated, the control system and the simulation models are designed. Then, the control system is simulated with Matlab/Simulink software.Fourthly, the suspension rotor displacement measuring technique is investigated. The dissertation, beginning from the bearingless induction motors' requests to displacement sensors, compares some non-contact displacement sensors. The characteristics of the eddy current displacement sensor are emphatically researched. Then, the installation of eddy current sensor, the rotor displacement detection system, and the errors in measuring system are investigated detailedly.Finally, the digital control system of the bearingless induction motor is designed using TMS320LF2407A DSP, then the design of hardware system and the development of software system are described detailedly. Based on the experiment prototype of the 2-degrees of freedom bearingless induction motor, the digital control system is debugged and optimized, and the correctness of digital control system and control strategy are verified by the experiments.