Research On Fuzzy Control Of AMB

Active magnetic bearing(AMB), which suspends the rotor by controlled magnetic force in a contact-free manner, is a high performance, novel type bearing. Of this special working mode, the AMB has many characteristics such as contact-free, no need of lubrication, low noise, low wastage and long life-span. As a result of those advantages before, AMB has important science significance and abroad application foreground in almost all of the fields of modern science and technology.AMB is a typical mechanical-electrical integration system, the performance of which mostly relied on the stabilization of selected controlled ways and means. Focusing on a magnetic bearing system with single degree of freedom, this article discusses several common control schemes, establishes simplified linear model of magnetic bearings control system. And through qualitative analysis influence of PID parameters on performance of control system, proposes variable parameters PID control which its control parameters is the function of displacement deviation and its time rate, gives a set of control function that can let rotor float steadily. Simulation shows that PID control parameter sets by chance, easy to cause system unstable.For overcome the defect of low response speed on PID control, the paper studied on fuzzy control. According to using the membership function of FIS system, cased the robustness of fuzzy controller poor, so used direct consulting method on input-output mapping table, researched on the accuracy of the mapping table on the control performance. In order to overcome steady-state errors of fuzzy control, proposed three methods to solve the issue:1>Integrated PID control and fuzzy control of their advantages and disadvantages, a Fuzzy-PID control method is proposed, which can cancel stable errors.2>Offset the expectation of fuzzy control, to offset system stable errors.3>Used switch to select, forcible constraint the system steady-state errors, realized the mean of stable errors zero. Simulation results show, these methods can reach the purpose of controlling bearing-rotor to expectation location. But under the high frequency interference, simulation show Fuzzy-PID control just back to switch threshold, expect excursion control, switch to pin control response fastest, can quickly return to balance position, but is larger in steady state ripple.