| Magnetic bearing is a new kind of bearing with high performance, which utilizes magnetic force to levitate the rotor in space. Magnetic bearings have changed traditional supporting form fundamentally, which arouse more attention due to the advantages of no mechanical contact, no pollution, no lubricated and seal, long life, and high-precision. They have latent application foreground in energy resource and communication, machinery industry, aeronautics and astronautics, and so on. At present, DC active magnetic bearings are mainly researched in the world. However, as the development of 3-phase power converter and DSP control technology, power converter has merits with lower cost, smaller volume, and reduce whole cost and volume for magnetic bearing driven control system. Supported by National Natural Science Foundation of China (50575099), the paper is researching a new structure of magnetic bearings driven by 3-phase converters, which is called as AC active magnetic bearings. The research includes mechanism structure, principle, mathematic models, control strategy, and displacement sensing technology for AC magnetic bearings. Based on coils’current ripple is a function of rotor displacement in magnetic bearing system driven by 3-phase power converter, in this dissertation displacement self-sensing technology is applied to AC active magnetic bearings system. Through displacement self-sensing circuit, rotor radial displacement signal is obtained indirectly by demodulating and filtering coils’current ripple, and then solve many problems such as mechanism size longer, cost higher, reliability lower which are caused by using displacement sensors. The detail contents are as follows:Firstly, the configuration and magnetic circuit of several kinds of typical active magnetic bearings are introduced. Based on the working principle of AC active magnetic bearings are analyzed, the mathematic models of magnetic suspension forces are deduced by using equivalent magnetic circuit. Based on mathematics models, nonlinearities of suspension forces and cross coupling between different degrees of freedom are analyzed by using simulation software MATLAB. Then control strategy of AC active magnetic bearings is proposed.Secondly, the working principle and characteristic of displacement self-sensing technology are described. Displacement self-sensing principle of AC active magnetic bearings system is analyzed in detail, and its circuits are designed. Based on introducing the function and principle of current tracking controller, the control block diagram of AC active magnetic bearings system is constructed and its performance is analyzed by simulating.Finally, using TMS320F2812 DSP of TI Company as a control chip, the hardware circuits of digital control system for AC active magnetic bearings with displacement self-sensing have been developed, the flow charts of main program and every subprogram have been listed. The related software is developed and part experiments are carried out. The detailed experimental and testing procedures have been proposed, which provides a good foundation for parameter debugging and performance analyzing on AC magnetic bearings with displacement self-sensing. |
