| The magnetic suspended rotor is high technology product. Because it has the advantages, such as frictionless, no wear, without lubricating, no pollution, low consuming and long life and so on, therefore, the magnetic suspended rotor is applied to high and super high speed, vacuum condition and some of the special condition and so on. It has broad application prospect and the important practical significance in the military, space, nuclear industry, energy and chemical industry, transportation and so on. Now magnetic bearings can be applied in practical engineeringand can implement active control, which is one of the bearing parts and has incomparable advantages of conventional bearings and supporting technology. Magnetic bearing has been used in various fields of high-speed rotating machinery at present. Along with the large scale enhancement of rotational speed of modern revolving mechanical, the supporting characteristic of magnetic suspended rotor has more and more influences on many fields, for example, rotor system’stability, dynamic characteristic, revolving precision.The magnetic bearing system has the performance of nonlinear dynamics and open-loop unstability, so the control system for magnetic bearing is needed. The magnetic bearing’s performance is highly depended on its control system. Using advanced control method is more important for magnetic bearing in order to meet the stability and robustness of the controller. Therefore, it was great significant to study the control methods for magnetic levitation system.Firstly, the magnetic bearing is introduced and the force of magnetic bearing is analyzed and decoupled in this paper. A single degree-of-freedom (1-DOF) magnetic levitation test-bed is designed. The sensor, performing organization and power amplifier’s performances of the control system are analyzed and selected. The force is particularly analyzed and mathematic model is established based on this1-DOF magnetic levitation test-bed. Studies of control theories are discussed according to this mathematic model. The controllers based on traditional control method (PID) and sliding model variables structure (SMVS) control method are discussed and simulated by MATLAB. The performances of both control method are compared. The results of simulation show that the SMVS control method has more stable and robust than PID control method. At the same time, it reduces the dynamic overshoots and shortens the adjustment time. The SMVS control method can rapidly reach the balance of system and has more power to restrain the interference signals compared with PID control method. Sliding mode variable structure control has the incomparable advantages in the application of mixed magnetic levitating bearing system. |
