Integrated Control of Torque and Suspension Force Considering Decaying Current of Bearingless Switched Reluctance Motor

In bearingless switched reluctance motor (BSRM) control system, decaying current will be generated after turn-
off
angle. If the decaying current cannot be controlled effectively, the stable control of torque and suspension force of BSRM during commutation region will be affected. An integrated control of torque and suspension force of BSRM based on dynamic phase commutation and currents distribution is proposed in the article. First, an optimization criterion of turn-
off
angle is proposed considering the effect of decaying current after turn-
off
angle on suspension control. The turn-
off
angle can be adjusted online according to the variation of radial displacement. Then, decaying currents after turn-
off
angle are used to modulate the current of incoming phase according to the difference of the torque generated by the neighboring phase. The optimization of turn-
off
angle and the distribution of phase currents ensure the high suspension stabilization and low torque ripple during phase commutation region of BSRM. Simulations and experiments on a three-phase 12/8 BSRM validate the feasibility and effectiveness of the proposed control strategy.