From the perspective of sensorless control for PMSM, this book analyzes and integrates the two control methods of high-speed and zero-low-speed ranges, to achieve full-speed control. A composite control based on weighted switching method is established, which effectively combines the good dynamic tracking performance of the model reference adaptive control method in the high-speed range and the high-precision control of the pulse injection method in the zero-low-speed range. The intermediate speed range where the two methods transition is controlled by the weighted method. Multiple control strategies are integrated and weighted according to the characteristics of PMSM operation at different speed ranges, ultimately overcoming the limitation of a single sensorless control method not being suitable for the full speed range. The PI structure of the speed adaptive law in the traditional model reference adaptive system will lead to the problems of reduced speed identification accuracy and poor robustness, the super-twisting sliding mode algorithm in the high-order sliding mode algorithm is proposed to improve the PI structure of the speed adaptive law in the traditional model.