Robust rotor position observers of sensorless interior permanent magnet synchronous motor for low-speed operation

Low speed control is a key technology to position sensorless interior permanent magnet synchronous motor (IPMSM) control systems. A robust rotor position observer based on high-frequency signal injection was proposed to improve low speed performance for sensorless IPMSM. The proposed position observer is aimed to enhance robustness to load disturbance. Phenomenons that position observer probably converges to opposite polarity position due to load disturbance was analyzed. Then, the structure of the robust observer was designed based on dynamic characteristic of load disturbance. Poles of the observer transfer function were designed considering step and ramp disturbances, as well as the expected estimation error value. Thus the feedback gain matrix could be calculated using the pole assignment method. Experimental results demonstrate the feasibility of the position observer by a position sensorless IPMSM vector control system.