H∞ Robust Controller Design and Experimental Analysis of Active Magnetic Bearings with Flexible Rotor System

H∞ controller for active magnetic bearings (AMBs) with flexible rotor system was designed in this paper. The motion equations of AMBs and flexible rotor system are built based on finite element methods (FEM). Weighting function matrices of H∞ controller for AMBs are studied for both the sensitivity and the complementary sensitivity of H∞ control theory. The simulation shows that the H∞ control method has a good dynamic characteristics, good robust and ability to depress vibration. The experiments are completed on a four-degree freedom magnetic bearings-flexible rotor test rig, and the obtained experimental results show that H∞ controller is characterized by the effectiveness of interference immunity and robust stability. The peak to peak vibration amplitudes of flexible rotor are less than 60μm at the first critical speed of flexible rotors, and the results indicate that H∞ controller for the active magnetic bearings with flexible rotor system is stable through the first critical speed of the flexible rotor system.