Research Of Magnetic Bearings Digital Control System And Experiment Based On The Grinder-polisher Electric Spindle

This paper summarized the recent active magnetic bearing (AMB) control technology from home and abroad. The mathematical model of AMB is set up. By analyzed its working course, the fully digital 5-degree-freedom magnetic bearing control system has been constructed. Based on combining theory, the sliding mode variable-structure control (VSC) method is discussed and the dynamics and nonlinear characteristic are studied. The experiment is presented.The state space model is established by analyzing the AMB control model theoretically. This paper supposed the suitable relation between the rotor's mass and equatorial moment of inertia and the position of fore-back magnetic bearings to get a minimum of inertia coupling. The control flow of decreasing gyroscopic coupling is presented.By means of studying model, the result as follows is obtained: Resonance from the whirling of rotor unbalance mass can be averted by carefully designing bearing stiffness to separate eigenfrequency from whirling frequency. The application of static or dynamic unbalance matrix to establishing model methods also increases efficiency. An appropriate balancing current and a set of indeplendent magnetic pole current can reduce magnetic coupling. The eccentric of rotor is considered as itself disturbances and overcome by variable-structure control.Based upon the analysis of the rotor uprising course, some new methods, current-symmetry current-dissymmetry and subsection control are originally put forward. To adopt grading control methods in balancing position increases the system stiffness and stability.On the basis of magnetic bearing control theory, and the use of stability criterion and pole placement, the digital control 5-degree-freedom MB is suspended. In addation, a simulation have been given for fully degree-freedom BM step pulse response and zero-pole position, some actual parameters about time and frequency domain Characteristic are achieved.The theoretical analysis proved that sensors occurred nonlinear structure-error. Experiments sometimes happened nonlinear characteristic occurring by system parameter Changing and exterior disturbance. This paper deals with magnetic saturation nonlinear characteristic using descriptive function method.The paper combined AMB model with VSC theory and discussed the existence condition of AMB slide model control, meanwhile, the generalizedslide mode range was given. It is proved that VSC bad the properties of excellent disturbance rejection stability and robustness. While the reaching condition was initialization the equivalent control equation of axial-radial variable structure control and sliding motion equation were given. The cause and eliminating method of VSC chattering were analyzed.The AMB system and experiment's platform have been designed and manufactured. Maximum carrying force and dynamic capacity also have been tested.At last, a few suggestions of further research and study of the project are put forward.