Research On Magnetic Bearing Control System

Magnetic Suspension Bearing, or Active Magnetic Bearing (AMB for short) is a kind of bearing with excellent performance, in which rotor can be suspended by magnetic force. Because of the perfect characteristic of contact-free between rotor and stator, the rotor can rotate at very high speed. Also, the AMB has the advantage of long lifetime, low power loss, low noise, no lubrication and almost no wear.The AMB system is instable in the condition of open-loop, it works well only with the help of a controller under closed-loop, which is very essential to the application of AMB system in research and industrial application. At present, the usual method is getting the linear model at the balance point of AMB system, designing a linear controller. But under control of the linear controller, the system has long settling time and large over-shoot. At the same time, the rotor's stable operating range is small. Therefore, the thesis tries to design a controller based on nonlinear model, such as T-S fuzzy model, to improve the system's dynamic performance and extend the rotor's stable operating range.In allusion to the shortcoming of small range under linear model, a suitable model that can well describe the AMB system's nonlinear characteristic must be found. Thus the first main part work is to model the AMB system with T-S fuzzy system. Two different models are established separately when the rotor is near to and far away from the balance point, then the two models' effective combination is taken as the system's final fuzzy model. The simulation results show that the fuzzy model not only can approach the high nonlinear relation of AMB system, but also can fit the system's various input-output data precisely.Hardware platform based on TMS320LF2407A and software design idea are introduced. And then the key problems are discussed. The various degrees of freedom at radial axis affect one another when the center is measured for suspended rotor. So the measurement can not be finished at one time. An iterative method with a successive-approximation is presented based on the center measurement of single degree of freedom. Some experimental data is given at the end of this thesis.