In view of the speed regulation and estimation problem of permanent magnet synchronous motor(PMSM), a speed
modulation system based on speed sensorless for PMSM is proposed. The adaptive fuzzy sliding mode soft switch controller is designed by using the replacement of sgn(x) function by tanh(x) function, which realizes the soft switch control and reduces chatting. A robust passivity-based control algorithm is constructed to obtain the ud and uq???? based on the passivity- based control principle. An adaptive sliding mode observer is established and a speed identification law is proposed, and the gain matrix of the observer is obtained by solving linear matrix inequalities. The simulation results show that the proposed strategy is effective, and the system has a satisfactory performance.