Performance analysis and digital control system design for AC 2-degree freedom hybrid magnetic bearing

In this paper, an AC 2-degree freedom hybrid magnetic bearing (HMB) is proposed, which is driven by a 3-phase AC power inverter. The configuration and the operating principle producing magnetic suspension forces of the AC 2-degree freedom HMB are introduced. By using equivalent magnetic circuit method, the calculation formulas of magnetic suspension forces and the mathematics models of the system are deduced. Nonlinearities of suspension forces and cross coupling between different degree freedoms are studied further by calculating the suspension forces at different displacements and control currents to validate the feasibility of the mathematics model. Then based on the mathematics models of the AC 2-degree freedom HMB, a digital control system of this novel bearing is designed based on TMS320F2812 DSP. The performances of digital control system of the AC 2-degree freedom HMB has been test by experiment. The anti-disturbance experiment has shown that the control performances of the digital control system of the AC 2-degree freedom HMB are well. This innovated AC 2-degree freedom HMB can be applied in high speed machine tool spindle with lower manufacturing and operation costs.