Speed sensorless control of permanent magnet-assisted bearingless synchronous reluctance motor based on enhanced linear extended state observer

The speed sensorless control of permanent magnet-assisted bearingless synchronous reluctance motor (PMa-BSynRM) is more challenging compared to conventional motors, as the coupling between suspension force and torque system increases the observer's estimation error. This paper presents a design method of a speed sensorless control system for PMa-BSynRM based on an enhanced linear extended state observer (ELESO). Firstly, the mechanism of the coupling of PMa-BSynRM suspension force system on the speed fluctuation is analyzed, and the mathematical model of torque system considering the coupling effect of suspension force is obtained. Secondly, a speed sensorless control method based on ELESO is proposed, and a proportional resonance controller is embedded in the original observer. The angular velocity obtained by the phase-locked loop (PLL) is fed back to the proportional resonance controller, enabling speed self-adaptation, enhancing the estimated bandwidth, and minimizing observation error in sensorless control. Finally, the proposed control method is verified by experiments on the digital control platform of PMa-BSynRM, and the experimental results prove the effectiveness of the proposed control method.