Dynamic stiffness control and acceleration scheduling for unbalance compensation in a rotor-bearing system: Experimental results

This work deals with the experimental application of an active unbalance compensation scheme for a rotor-bearing system by simultaneously using two control strategies, consisting in the synthesis of a dynamic stiffness controller and the acceleration scheduling for the rotor speed. The rotor-bearing system consists of an asymmetrical rotor system with a servomechanism to position a sliding bearing support such that the rotor lateral dynamics can be modified by controlling the effective rotor length and, therefore, the natural frequencies can be arbitrarily shifted into a small range, where the resonance can be passed and attenuated during run-up or coast-down operations. The dynamic stiffness control is performed by applying a fast and robust PD feedback control scheme and the rotor speed is controlled to asymptotically track a smooth speed profile, adjusted to reduce the unbalance response when the rotor passes over the first critical speeds. The overall unbalance response in the rotor-bearing system can be reduced up to 42.5% with respect to the open-loop response, which is validated with experimental results on a testbed.