A disturbance rejection approach is presented for a class of uncertain systems subject to sinusoidal disturbance with unknown frequency. The proposed disturbance estimation method includes two types of observers that are connected in cascade form. The disturbance property is excited through an auxiliary filter, and then a frequency factor observer is constructed to generate the information required by full-order state observer. Thus, with the disturbance and system state estimation values, the composite control structure including a cascade disturbance observer (CDO) and a robust feedback controller is designed. As a result, the uncertain system with unknown-frequency sinusoidal component can be controlled within the disturbance observer-based control (DOBC) framework, where the asymptotic stability performance can be guaranteed.

针对一类具有未知频率正弦扰动的不确定系统，提出了一种干扰抑制方法。所提出的干扰估计方法包括以级联形式连接的两种类型的观测器。通过辅助滤波器激发干扰特性，然后构造频率因子观测器以生成全阶状态观测器所需的信息。因此，利用干扰和系统状态估计值，设计了包括级联干扰观察器（CDO）和鲁棒反馈控制器的复合控制结构。结果，具有未知频率正弦分量的不确定系统可以在基于扰动观测器的控制（DOBC）框架内进行控制，从而可以保证渐近稳定性能。