The Radial Active Magnetic Bearing And Its Digital Control System

Active magnetic bearings(AMB) is a new kind of product applied in rotating machinery ,which can use controllable electromagnetic force to support a rotor freely. Compared with the conventional rolling element or journal bearings,it is non-friction and need no lubrication even when operating in high speed ,and its dynamical property is adjustable,so it attract the attention of science and enterprise fields.The application of AMB is high technology which concerning many fields such as magnetics , mechanics, rotor dynamics , control theory and computer science.This paper analyses the working principle of AMB firstly , then derive the relationship between electromagnetical power and rotor displacement under the single degree of freedom,and a mathmatical model is established at last.In control system, the monitoring part use no sensor but electromagnet itself to monitor the rotor displacement.This is a trend in AMB development because it not only cut down whole cost but also optimize control effect.As for the mathmatical model,there were two control algorithms.One is conventional PID and the other is improved one which combines the advantages of PID and fuzzy controller. Because of the advantages, it make overshooting number smaller and reaction time shorter ,also can adjust the parameter by itself, so this algorithms is very suitable for non-linear system.After simulinking on matlab platform, simulating on real hardware is needed. First of all, the controlled object of AMB can be transformed into simulative object by an electrical circle board , then use another one to control the simulative object. The two electrical circle boards also use the chip C8051F120. The results putting in computer show that the control effect is almost same as simulinking on matlab and can meet the need of AMB control system.