Design and performance of QFT-H-infinity controller for magnetic bearing of high-speed motors

Magnetic bearings can not only solve the bearing wear and life problems but also reduce the loss and noise of bearings. However, the strong non-linear and uncertainty of parameter of the magnetic bearings make the traditional PID controller difficult to ensure its long-term and stable operation. Based on the theory of quantitative feedback theory (QFT) and H_infin control theory, this paper presents a design method of magnetic bearing controller for high speed motors. QFT is able to implement design requirements to robust stability and robust performance of the system with large scope uncertainties, but it requires loop-shaping on the Nichols chart and tedious graphical process. Based on QFT, the adoption of H_infin control theory can reduce the drawing process which greatly simplifies the design process. The simulation and experimental results show that the proposed QFT-H_infin controller makes the control system of magnetic bearings have a strong anti-jamming performance for uncertainty of parameters and loading disturbances to ensure the long-term stable operation of the magnetic bearings.