The Dynamic Behavior Of Active Magnetic Bearing & Parameters Of PID Controller's Optimization

Active Magnetic Bearing(AMB) is one of typical mechatronic products and a new type high performance bearing piece. It has the properties of no friction, no fray, dispense with lubricate, lasting life, all extrude excellence above which can't be seen in traditional roll bearing and sliding bearing. With the technology of AMB is known and mastered gradually, AMB will be applied to these fields far and widely: aviation and space flight, vacuum technology, machine tool and tail-wagging engine, energy source and traffic, and so on.However it is an obstacle to the development of AMB that the structure dynamics of a rotor is not taken into account in design of AMB control system and in the control design of AMB there is no method to consider the structure dynamics of a rotor. In fact, performances of AMB are depended on both of AMB's control system and rotor's structure dynamics. By means of AMB, the rotor system can obtain suitable stiffness and damp.Based on analyzing kinematics of the spindle unit under loading, the mathematical models of rigid and flexible rotor system are established. The support of AMB is elastic. The elastic effect is different from the effect of rigid support, In this paper, a spindle is simplified as one-disc rotor or multi-discs rotor. By the rules of Riccati transfer matrix, the varieties of dynamic properties, inherent frequency and main vibration model of the rotor are calculated.The most important field of AMB research is the research of the controller of the AMB. The performance of the controller affects the dynamic performance of the AMB system and the circumgyration precision of the rotor, which is very important to the application of the AMB. The four models of the controller are put forward after analyzing the two shortcomings of typical PID controller. Through simulation and calculating the four models, the influence on proportion coefficient, integral time constant, derivative time constant and partial feedback coefficient for system performance is analyzed. The ideal reference value of every parameters and step respond curves are given. Thesimulation result may be used as reference for making analogue controller or digital controller.