Abstract：Permanent magnet synchronous machines（PMSM）has serious chattering problem when traditional

sliding mode observer（SMO）is applied to low-speed operation with fixed sliding mode gain. To solve this

problem，a full-order sliding mode observer（FSMO）with fuzzy adaptive adjustment of sliding mode gain was

proposed，which can improve the chattering suppression performance in a wide speed range. First，a FSMO was

constructed with stator current and extended back-EMF as observation objects. In addition，the fuzzy control rules

were constructed by using the error and error change-rate of the actual and observed values of the stator current as

the input，and the adaptive adjustment of the sliding mode gain was realized according to the different speed of the motor. Then，the soft switching continuous sliding mode control was realized by using hyperbolic tangent function instead of traditional sign function. Moreover，in order to eliminate the influence of variable speed，the normalized orthogonal phase-locked loop was used to obtain the accurate rotor position from the extended back-EMF. Finally，the PMSM drive test platform was built，and the performance of low speed and medium-high speed was tested. The experimental results show that the proposed algorithm has significant advantages in wide speed range over traditional algorithms.

      Key words：permanent magnet synchronous machines（PMSM）；full-order sliding mode observer（FSMO）；

fuzzy adaptive control；sensorless control；hyperbolic tangent function