A Smooth Switch between Different Unbalance Control Parameters in Rotor Systems with Active Magnetic Bearings

Unbalance control is necessary for rotor systems with active magnetic bearings (AMBs), especially for vibration sensitive applications such as flywheels and turbo molecular pumps. When a special unbalance control method is used in an AMB rotor system, its key feedback parameters such as gain matrix parameters are usually closely related to the AMB model, which changes with the rotation speed of the rotor. For simplicity and convenience, the feedback gain parameters can keep constant in a special speed range and change to different new constant values when the rotation speed enters a close range. It is also possible to use a special method in the previous speed range and use another method in the close range. The switch between unbalance control algorithms needs a suitable method to ensure the stability and smoothness of a switch process. Different switch methods including a direct switch method, a linear switch method and an overlying switch method are introduced and verified in a flywheel system with AMBs. Their effects in switching between two General Notch Filter matrices were verified by simulation and experiments. The simple overlying switch method proved its performance and achieved a very stable and smooth algorithm switch.