Abstract: Aiming at the problem of poor robustness and anti-interference ability in Permanent Magnet Synchronous Motor (PMSM) speed control system, an Improved Fractional Order Active Disturbance Rejection Controller (IFOADRC) is proposed to replace the traditional active disturbance rejection controller. First, a new nonlinear function is designed and applied to the Nonlinear Fractional Order Extended State Observer (NFOESO). The Linear Fractional Order Extended State Observer (LFOESO) is used to make preliminary observations of the total disturbance, and then the designed weight function is used to introduce the estimated results into the nonlinear fractional extended state observer. Secondly, the Improved Fractional Order Active Disturbance Rejection Controller (IFOADRC) is established, and the convergence and interference suppression ability of the control strategy are analyzed theoretically. Finally, Simulink simulations and links-RT hardware-in-the-loop experiments are conducted to validate the proposed control strategy. Experimental results demonstrated that, compared to the traditional Nonlinear Active Disturbance Rejection Controller (NLADRC) and Cascaded Linear Active Disturbance Rejection Controller (CLADRC), the proposed control strategy achieved the following improvements: during speed step inputs, the settling time was reduced by 25.6 % and 17.6 % during acceleration, and by 10.7 % and 5.6 % during deceleration; during load disturbances, the settling time was reduced by 51.9 % and 24.2 % during sudden load addition, and by 41.5 % and 22.6 % during sudden load reduction. These results validate that the proposed control strategy effectively enhances the robustness and disturbance rejection capability of permanent magnet synchronous motors.

Key words: Active Disturbance Rejection Control (ADRC), Permanent Magnet Synchronous Motor(PMSM), cascade expanded state observer, fractional calculus