A Study On The Bearingless Permanent Magnet Synchronous Motor Based On H_∞ Control Theory

The bearingless permanent magnet synchronous motor is easier to achieve high speed and big power than normal motors because its rotor suspending. And it has extensive applied foreground in the cleanness domain because it avoids rub and pollute. The bearingless permanent magnet synchronous motor is a system with many variables and strong coupling. Considering the coupling between the torque and suspension subsystem, and the coupling between X direction and Y direction, the controller must be robust and adapt to MIMO system. The H_∞controller is robust for the system under disturbance and system parameter variations if the three weight functions are selected properly.A H_∞regular based on the mixed sensitivity method is designed for the speed subsystem of a PM type bearingless motor in this paper, and the model order of the controller is reduced based on the balanced realization. The result of the simulation and experiment show the controller can ensure the stable error within 1r/min and the motor with strong robustness under disturbance and system parameters variations. A H_∞controller for the suspension subsystem of a bearingless permanent magnet synchronous motor is designed, and the responses of the bearingless permanent magnet synchronous motor under disturbance and system parameters perturbation are investigated by simulation model. Simulation results and the comparison with the effect of the PID controller show that the H_∞controller is able to ensure the system with strong robustness and excellent disturbance attenuation performance.Controllers for the suspension subsystem are designed according to LQG/LTR control theory, H₂/ H_∞control theory and H2 control theory. Simulation verified the design.