Control Strategy For Active Magnetic Bearing System Based On Variable Bias Current

Employing both the PID and the robust H∞control strategy, the dynamic performance of theactive magnetic bearing (AMB) system with variable bias currents and zero bias current is studied inthis paper.Firstly, the stable regions of the system with different bias currents under the condition of the PIDcontrol strategy are obtained through static suspension experiments. The influence of bias current andPID control parmeters on dynamic performance of the system is investigated by simulation analysisand operating experiments of the system. Moreover, the mathematic model of the system isestablished under the condition of the mixed sensitivity H∞strategy. A new method to select theweighting functions according to the vibration amplitude of the rotor operating at the critical speeds ofthe system is put forward. The digital controller following the mixed sensitivity H∞strategy isdesigned and validated by simulation analysis and operating experiments of the system.The results show that, the method to select the weighting functions for the system with theflexible rotor is efficient in this paper. Dynamic performance of the system with variable bias currentscan be guaranteed and the total currents of AMBs can be reduced obviously. In addition, comparedwith the PID control strategy, the AMB system under the condition of the H∞control strategy hasbetter dynamic performance.