Control of Active Magnetic Bearing systems on non-static foundations

A case study of an electric motor with Active Magnetic Bearings (AMBs) that is subjected to the waving of the supporting foundation is presented. The motor is intended for sea applications where the ship is disturbed by the oscillation of the waves. Initially, a tilt-and-translate PID controller is designed to stabilize the rotor in the magnetic bearing system and satisfy the Zone A specifications defined by the International Organization for Standardization (ISO 14839) for new machines with magnetic bearings. The performance of the tilt-and-translate controller is then tested when the motor is subjected to the waving of the foundation. Simulation shows that the rotor vibration level easily exceeds the permitted level by the ISO specifications due to a combination of the waving disturbance from the foundation and the gyroscopic forces. Based on the results with the tilt-and-translate controller, a robust μ controller is designed to reduce the vibration of the rotor. The performance of the controller is tested when subjected to the waving of the foundation, and simulation shows that the vibration level is reduced to the level permitted by the ISO specifications.