Robust control method for disturbance rejection on axial magnetic bearing

Considering the requirements of robust stability and dynamic performance to reject disturbance, the problem of low bandwidth was analyzed when applying the disturbance observation(DOB) in the magnetic bearing. It was pointed out that the magnetic bearing was affected by outside low bandwidth noise, then a robust disturbance rejection method was proposed. The nominal model of the axial magnetic bearing was set up through dynamic analysis. And the DOB for internal loop controller was designed consisting of the inverse nominal model and a low pass filter with two relative rank. In external loop, a robust controller is developed using standard H_∞ analysis method after choosing proper weight functions to enhance robust stability. The simulation analysis and experiment result indicate that the method could extend the bandwidth of the DOB. Comparing to single controller, experimental result verifies that the robust disturbance rejection system controller has broad robust stability margin on parameter uncertainty and strong ability to eliminate disturbance.