Extended state observer (ESO) is a class of high-gain observers and a powerful tool for output feedback control of uncertain nonlinear systems. In this paper, we propose a new ESO design technique which is based on cascading a series of first-order ESOs. Benefited from the cascade design, saturations can be inserted into the observer internal variables to limit the maximal implemented gain. The convergence of the new ESO with a class of nonlinear gain functions is established, and it is shown that adopting appropriate nonlinear gain mechanisms leads to improvement in measurement noise tolerance. What is more, the new ESO based output feedback control has stronger uncertainty estimation and compensation capability than the standard ESO based output feedback control. Specifically, the proposed approach only relies on the knowledge of the control direction of the uncertain nonlinear system. Finally, the obtained results are applied to suppress the wing rock motion of a slender delta wing.

扩展状态观测器（ESO）是一类高增益观测器，是不确定非线性系统输出反馈控制的有力工具. 在本文中，我们提出了一种新的 ESO 设计技术，该技术基于级联一系列一阶 ESO。受益于级联设计，可以将饱和度插入到观察器内部变量中以限制最大实现增益。建立了新的 ESO 与一类非线性增益函数的收敛性，表明采用适当的非线性增益机制可以提高测量噪声容限。更重要的是，新的基于 ESO 的输出反馈控制比基于标准 ESO 的输出反馈控制具有更强的不确定性估计和补偿能力。具体而言，所提出的方法仅依赖于不确定非线性系统的控制方向的知识。最后，将所得结果应用于抑制细长三角翼的翼岩运动。