In this paper, a robust control scheme using back-stepping and α-filter-based uncertainty and disturbance estimator (UDE) is designed for flexible air-breathing hypersonic vehicle (FAHV) in the presence of severe external disturbances. Firstly, with the aid of back-stepping technique, the longitudinal dynamics of FAHV is separated into velocity and altitude subsystems. Feedback linearization (FL) is utilized to design control laws for each subsystem. Secondly, to enhance robustness of the controller, α-filter-based UDEs are constructed to estimate the lumped disturbances, including aerodynamic parameter uncertainties, flexible effects and external disturbances. More importantly, the performance superiority of α-filter-based UDE is clarified via frequency response analysis and comparisons with an extended state observer (ESO). Furthermore, the issue of tuning design parameter α is analyzed. The stability of closed-loop system is proved by Lyapunov stability theory. Simulation results demonstrate the effectiveness of the proposed control strategy.

中文翻译：

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基于α滤波器的不确定性和扰动估计器对柔性吸气式高超声速飞行器的反步鲁棒控制

在本文中，使用反步法和基于 α 滤波器的不确定性和扰动估计器 (UDE) 的鲁棒控制方案设计用于存在严重外部扰动的柔性吸气式高超声速飞行器 (FAHV)。首先，借助反推技术，将FAHV的纵向动力学分解为速度子系统和高度子系统。反馈线性化 (FL) 用于为每个子系统设计控制律。其次，为了增强控制器的鲁棒性，构建了基于 α 滤波器的 UDE 来估计集总扰动，包括气动参数不确定性、柔性效应和外部扰动。更重要的是，通过频率响应分析和与扩展状态观测器 (ESO) 的比较，阐明了基于 α 滤波器的 UDE 的性能优势。此外，分析了调整设计参数α的问题。Lyapunov稳定性理论证明了闭环系统的稳定性。仿真结果证明了所提出的控制策略的有效性。