Aiming at the stability and others properties of active magnetic bearing （AMB） system influenced by the periodic unbalance stimulation synchronous with rotor rotational speed, a new real-time adaptive feed-forward unbalance force compensation scheme is proposed based on variable step-size least mean square（LMS） algorithm as the feed-forward compensation controller. The controller can provide some suitable sinusoidal signals to com- pensate the feedback unbalance response signals synchronous with the rotary frequency, then reduce the fluctua- tion of the control currents and weaken the active control of AMB system. The variable step-size proportional to the rotational frequency is deduced by analyzing the principle of normal LMS algorithm and its deficiency in the application of real-time filtering of AMB system. Experimental results show that the new method can implement real-time unbalance force compensation in a wide frequency band, reduce the effect of unbalance stimulant force on the housing of AMB system, and provide convenience to improve rotational speed.
振动分析是研究主动磁悬浮轴承(Active magnetic bearings,AMB)系统的一个重要部分,但是目前结合控制器以及动态不平衡响应建立的系统数学模型相对较少。通过对高速主动磁悬浮轴承转子系统受力分析,参考所使用的不完全微分PID控制器的频率特性对AMB广义动刚度的影响以及对转子动态不平衡激励响应的影响,建立径向子系统的力学振动方程。通过此振动方程的解,得出AMB系统存在的振动形式。一种是由于系统固有频率存在而产生的自由振动,另一种是由于不平衡响应存在而产生的简谐振动,并解释当两种振动频率相近时系统所产生的拍振现象。通过调节控制电流主动控制作用,可以改变磁悬浮轴承广义动刚度,进而改变系统固有频率,最终起到减弱拍振现象作用。仿真和试验能够验证拍振现象以及改变主动控制作用后的减振效果。此力学模型可为AMB系统不平衡振动补偿算法研究提供仿真平台。
