LAUSR

A novel $d$ -axis variable-structure control (VSC) current regulator is proposed for realizing fast and accurate sensorless control in the surface-mounted permanent magnet synchronous motor (SPMSM) in this article. In this proposed regulator, the sigmoid function is employed as a switching control law to reduce the chattering effect and increase the degrees of freedom in tuning the regulator. The sensorless control performance under the $d$ -axis VSC current regulator is testified by using the model reference adaptive system (MRAS) and sliding-mode control (SMC) method. In the MRAS observer, the adaptive law of speed and resistance is designed so that resistance, speed, and position can be estimated simultaneously, which can eliminate the influence of the resistance variations theoretically. In the sliding-mode observer, the back electromotive force observer is employed to estimate the speed and position of PMSM so that the estimation can cover a relative low-speed range because pure integration is not employed. Furthermore, the dead-time compensation voltages (DTCV) strategy is employed to online estimate disturbance voltage in a feed-forward manner, which can improve the sensorless control performance of PMSM. Experimental results obtained from an SPMSM drive system validate the superiority of the proposed $d$ -axis VSC current regulator.