针对典型二阶系统状态方程，在有扰动情况下设计带有扩张状态观测器的自抗扰控制器，控制器设计方法参见韩京清先生的《自抗扰控制技术》。(According to the state equation of typical two order system, an active disturbance rejection controller (ADRC) is designed in the case of disturbance. The controller design method is described in detail by Mr. Han Jingqing's active disturbance rejection control technique.)