Research On Automatic Balance Control Of Active Magnetic Bearing-rigid Rotor System

Active magnetic bearing(AMB)is a kind of non-contact,controllable supporting unit of the rotor system.By applying electromagnetic force to the rotor,it can maintain the suspension and friction-free state.It has the characteristics of no mechanical friction and no lubrication.At the same time,it can also be controlled by active control strategy.The stiffness and damping characteristics of the rotor system are adjusted online to improve the rotor vibration characteristics.This paper studies the unbalanced vibration control method of a four-degree-of-freedom AMB-rigid rotor system.Under the premise of tuning the parameters of the closed-loop decentralized PID controller according to the stiffness and damping characteristics of the rotor system,an automatic balance based on the adaptive gain coefficient is proposed.The control method aims to study the automatic balance control of a four-degree-of-freedom AMB-rigid rotor system.Firstly,the system structure and working principle of the AMB-rigid rotor system are explained,and the single degree of freedom mathematical model of the AMB is established.Then,based on the construction of the two degree of freedom plane rotor model,the dynamic imbalance of the rotor is considered.The dynamic model of the radial four-degreeof-freedom AMB-rigid rotor system is analyzed,and the open-loop stability and vibration characteristics of the system are analyzed.In the design of the closed-loop decentralized PID controller of the system,this paper aims at the problem of the unclear physical meaning of the parameters of the decentralized PID controller commonly used in the AMB-rigid rotor system and the lack of parameter setting basis.By deriving the four-degree-of-freedom AMB-rigidity The analytic relationship between the system stiffness and damping and the controller parameters,and then the influence of acceleration motion is considered,and the setting methods of bias current,proportional coefficient and differential coefficient are given.Finally,the stability and vibration characteristics of the system under different controller parameters are analyzed in combination with simulation,which serves as the basis for studying system vibration control methods.Aiming at the unbalanced vibration problem of the AMB-rigid rotor system,an improved adaptive vibration control strategy is proposed on the basis of the traditional notch filter automatic balance control scheme.The rotor is rotated through coordinate transformation and inverse transformation of the rotor center of mass.The same-frequency vibration is converted into a low-frequency signal,and then the same-frequency vibration signal is filtered out by an adaptive variable gain low-pass filter,so as to realize the automatic balance control of the system.In this process,an adaptive fixed-step/variablestep adjustment algorithm for the gain coefficient of the low-pass filter is added,and the stability of the system after the introduction of automatic balance control is further analyzed.On the basis of simulation analysis,experiments were carried out using the four-degree-offreedom radial AMB-rigid rotor system experimental platform,which verified the effectiveness of the proposed method.