摩擦非线性造成机载光电跟踪平台伺服系统低速不平稳性，增加了系统的稳态误差。常规PID 控制难以满足光电跟踪平台高精度伺服系统的性能要求。采用一种新的二阶离散系统最速控制函数设计自抗扰控制器，将它作为机载光电跟踪平台伺服系统的位置环控制器。实验结果表明，当系统跟踪幅值为0.5°、频率为0.159 Hz 的正弦输入信号时，在0.5 s 之后，采用自抗扰控制的光电跟踪平台伺服系统的位置跟踪误差小于±(4.1×10-3)°，速度跟踪误差小于±0.024°/s，说明该自抗扰控制器有效地补偿了摩擦非线性，提高了伺服系统的位置和速度跟踪精度。

The friction nonlinearity in the servo system of an air-borne opto-electronic tracking platform causes creeping phenomena in the lower velocity and increases the steady error of the servo system. It is difficult for the routine PID controller to satisfy performance specifications of the high precision servo system of the opto-electronic tracking platform. An Active Disturbance Rejection Controller (ADRC) with a new control function of the second-order discrete system is studied. The new ADRC is used as the position-loop controller in the servo system of the air-borne opto-electronic tracking platform. The experimental results show that the position tracking error of the servo system is less than ±(4.1×10-3)° and the velocity tracking error is less than ±0.024°/s after 0.5 second when the servo system tracks the sine input signal whose amplitude is 0.5° and frequency is 0.159 Hz. They demonstrate that the ADRC increases the position and the velocity tracking precision of the servo system through effective compensating the friction nonlinearity.