Cross-coupling and Unbalance Compensation of a Rigid Rotor

The system under investigation is a rigid rotor supported by two active magnetic bearings. In this paper two coexisting sources of vibrations are considered. First, mass unbalance excitation as a synchronous periodic disturbance and second, destabilizing cross‐coupling forces as generated, for example, by fluid film mechanisms, annular pressure seals or labyrinths of a turbo machine. The basic AMB‐control is carried out by a simple PID controller while for the compensation of both excitation mechanisms two independent control algorithms are used. In order to compensate the destabilizing cross‐coupling forces a least square estimator estimates the unknown parameters of the cross‐coupling mechanism. The mass unbalance forces are compensated by a recursive gain scheduled algorithm. By combining these two algorithms a significant reduction of the vibration level is achieved.