为了改善传统滑模观测器(SMO)无传感器永磁同步电机(PMSM)高频抖振问题，提高无传感器PMSM观测性能，在传统SMO的基础上采用Sigmoid函数作为切换函数以减小抖振。同时，通过低通变截止滤波器和卡尔曼滤波器组合的级联滤波器进行滤波以去除高频信号，并降低测量噪声和测量误差，最后运用锁相环技术(PLL)提取电机转速信息和位置信息。采用MATLAB/Simulink仿真的手段来验证改进的SMO有效性和可行性。仿真结果表明，采用改进的SMO比传统SMO具有更高质量的观测信号，并且控制系统动态和静态性能较好。

In order to reduce the high frequency chattering of sliding mode observer (SMO) of sensorless permanent magnet synchronous motor (PMSM) and improve the observer characteristics, on the basis of conventional SMO, Sigmoid function is used as the switching function to decrease system chattering. Meanwhile, the combination of the low-pass variable cutoff frequency filter and Kalman filter is used to filter high frequency signals and decrease measurement noise and errors. At last, the speed and position of PMSM are acquired by using phase locked loop (PLL) technique. The effectiveness and feasibility of SMO are verified by MATLAB/Simulink simulation. The results show that the improved SMO has higher quality observation signals than conventional SMO, and the dynamic and static characteristics of the control system are also better.