Disturbance Accommodating Controllers for Rotating Mechanical Systems

Abstract

The use of magnetic bearings for supporting a rotor-shaft system has led to increasing interest in active control schemes. In this work, two disturbance accommodating controllers are developed which minimize the vibration of the system due to the mass imbalance of the rotor. The first controller generates an estimate of the disturbance force arising from this mass imbalance and then cancels its effect through the magnetic bearings. This keeps the rotor displacement at zero but often at the expense of high bearing forces. The second controller remedies this by estimating the eccentricity and then applying a force to the controlled shaft end to offset the effect of the eccentricity. This requires the controlled shaft end to follow a path so that the rotor shaft pivots about the center of mass. Thus, the center of mass of the system does not translate and so a disturbance force never occurs. Therefore, a small magnetic bearing force can be used to control the vibration of a large rotor. Both methods are compared to conventional bearing strategies.