MAGNETIC BEARING CONTROL OF FLEXIBLE SHAFT VIBRATIONS BASED ON MULTIACCESS VELOCITY-DISPLACEMENT FEEDBACK

A model of the forced vibrations of a flexible, asymmetric and unbalan ced shaft, supported by two magnetic bearings, is derived to simulate the effect of different schemes of active control on shaft dynamic beh avior. Simulation results were compared for several cases of single an d multi-access bearing controls, rigid-body mode only and rigid with f lexible mode control, and linear and nonlinear bearing responses. It i s shown that the multi-access bearing response, calculated from the kn own equation of the stable ROCL (Reduced Order Closed Loop) and based on the direct velocity-displacement feedback, provided the most precis e shift in critical frequencies and also reasonable suppression of sha ft vibration amplitudes. The nonlinear bearing design was also briefly discussed. The stability analysis showed that stability limits were i nfluenced by more parameters in this case, but no particular advantage s were observed in suppression of the vibration amplitudes as compared to the linear case.