Surface permanent magnet machine self-sensing at zero and low speeds using improved observer for position, velocity, and disturbance torque estimation

This paper proposes an improved method for the estimation of position, velocity and disturbance torque in a surface permanent magnet (SPM) machine self-sensing (position sensorless) drive that uses high frequency (HF) voltage injection. SPM machines traditionally do not have enough position dependent signals because their symmetric rotors result in near zero spatial saliency. A separate disturbance observer and a saliency-tracking observer with speed-varying bandwidth (BW) tuning are used together to improve the disturbance rejection performance while maintaining the accuracy of self-sensing position and velocity estimation. According to the experimental evaluation, the proposed estimation method can achieve higher BW for the disturbance estimation and decoupling which can increase the stiffness of SPM machine closed-loop self-sensing control. This paper includes experimental comparative evaluation of closed-loop encoder-based versus closed-loop self-sensing-based operation of a SPM machine drive.