To address the challenges of accurately estimating rotor speed and position using the Sliding Mode Observer (SMO) due to high-frequency chattering,and the poor robustness and speed tracking performance of the speed loop PI controller,we propose an improved SMO-based speed sensorless control scheme for Permanent Magnet Synchronous Motor (PMSM).First,an Infinite Impulse Response (IIR) filter is incorporated into the SMO within the Direct Torque Control (DTC) system to mitigate the high frequency noise in the SMO output.Then a continuous hyperbolic tangent function is adopted to replace the discontinuous sign function to attenuate the system chattering.Moreover,an Active Disturbance Rejection Control (ADRC)-based speed loop controller is designed to optimize the trade-off between the overshoot and settling time of the system.Finally,a hardware-in-the-loop experimental platform is established in Matlab/Simulink environment.Both simulation and experimental results show that,under identical load and interference conditions,the proposed ADRC-based speed sensorless controller outperforms traditional speed sensorless control systems,effectively suppressing the chattering and exhibiting superior robustness and speed tracking performance.