针对电动舵机系统的非线性、快时变等特点，提出了改进的自抗扰控制器以改善系统的位置跟踪性能。首先，给出电动舵机的系统模型及控制策略，分析了系统中非线性因素的影响; 设计了改进自抗扰控制器，并利用现代控制理论给出了控制器参数的选择方法。然后，在舵机系统中进行仿真分析，验证了该控制器的可行性。最后，基于谐波式电动舵机对改进的自抗扰控制器与常规自抗扰控制器及PI控制器进行对比实验。实验结果表明: 跟踪10 sin(5 πt)正弦信号时，改进自抗扰控制器能够消除位置平顶和速度死区，相位滞后为0.087 22 rad; 跟踪±1°~±15°角位置时，上升时间为9~18 ms，超调量为0~7.25%，稳态均方差为0.007 60~0.010 83，性能明显优于常规自抗扰控制器和PI控制器。得到的数据显示该控制器减少了设计参数，位置跟踪超调量小，响应时间快，稳态均方差小，改善了舵机系统的动态和稳态性能。

Because Electromechanical Actuator (EMA) is a nonlinear, time-varying servo system, this paper proposes an improved Active Disturbance Rejection Controller(ADRC) to improve the tracking performance of the EMA. First, the mathematical model and control strategy of the EMA were presented and the nonlinear factors influencing the performance of EMA were analyzed by the control theory. Then, the improved ADRC was described and the method to select parameters were given by modern control theory. Furthermore, the feasibility of this controller was demonstrated through a simulation under different input conditions. Finally, the performance of PI controller, ADRC, and improved ADRC was compared by experiments on a harmonic drive EMA servo system. Experimental results indicate that the improved ADRC controller can remove the position flat crest and velocity dead space, and its phase error is 0.087 22 rad when the angular position signal of 10 sin(5 πt) is tracked. Furthermore, the rise time, overshoot and the steady state mean square deviation of EMA system are 9-18 ms, 0-7.25%, 0.007 60-0.010 83, respectively, when ±1°-±15°angular positions are tracked. These results means that the performance of the improved ADRC is better than those of the PI controller and traditional ADRC. It has a fast response, slight overshoot and high accuracy in stability, as well as strong anti-disturbance and robustness.