Experiments on ROLAC to Recover Rotor Position Following Contact

There is growing interest in magnetic bearing applications because of their advantages for contactless support, high-speed operation, vibration control, condition monitoring and fault diagnostics. However, they have limited force capacity and have to incorporate retainer bearings to protect the laminations when vibration levels reach the clearance level. Retainer bearings can take a relatively small number of rotor drops followed by machine shutdown. There are many potential applications where transient events or sudden changes in operating conditions could drive the rotor into contact with retainer bearings. These include land, sea and air transport applications, which are exposed to external inputs and disturbances, and system shut down is not acceptable. This paper describes the application of a Recursive Open Loop Adaptive Controller (ROLAC), an adaptive and fast acting controller, to prevent contact between a flexible rotor and retainer bearing. If however contact does occur, then the control action will minimize the damage and recover the rotor position without the need to shut down the system. It is assumed that the magnetic bearings are fully operational and contact is due to external disturbances such as sudden un-balance, base excitation, blade loss or damage. Experimental results are presented to demonstrate the effectiveness of the control algorithm.