Digital Control Of Active Magnetic Bearing System With Variable Bias Current

Coil current of ordinary Active Magnetic Bearing (AMB) is composed of bias current and control current. To reduce power loss of AMB, two kinds of analog controller are developed in the thesis. One is used in the system with zero bias current in axial degree of freedom and bias current mode in radial degrees of freedom, the other is used in the system with zero bias current modes in five degrees of freedom. Dynamic performances of the system with the two controllers are investigated separately. The results show that, compared with ordinary AMB system, zero bias current mode in axial degree of freedom has less effect on the dynamic performance of the system, while zero bias current mode in radial degrees of freedom degrade the dynamic performance of the system obviously.On the foundation of above research, the digital control hardware based on TMS320F2812 DSP is designed and manufactured for the system, variable bias current PID control program is developed by C and assembly language, and the experiments of suspension and high-speed rotating of the setup are also finished. The results show that bias current mode in radial degrees of freedom should be adopted when the system is operated near the critical speeds so that the system has super performance, while low bias current mode in radial degrees of freedom should be adopted when the system is far from the critical speeds so that the power loss of AMB could be reduced.