An improved continuous sliding mode control algorithm is proposed for a flexible air‐breathing hypersonic vehicle (FAHV), including nonsingular fast fixed‐time sliding surface (NFFS) and dual‐layer adaptive continuous twisting reaching law (DACTL). Firstly, the nonlinear control‐oriented model of FAHV is processed using input/output feedback linearization method with the significant flexible effects modeling as unknown matched disturbances. Secondly, a novel NFFS is improved from conventional fixed‐time sliding surface by adjusting power exponent to accelerate convergence rate. In the meanwhile, in order to avoid singularity aroused by fractional power term, an exponential convergent sliding surface is switched when tracking error approaches zero. Thirdly, a DACTL is proposed to realize finite‐time convergence of sliding mode variable with higher convergence precision and less chattering. Dual‐layer adaptive law is utilized to adjust the gain in DACTL based on equivalent control concept so as to enhance robustness automatically and avoid overestimation of control gain. Meanwhile, disturbances can be compensated without knowledge of Lipschitz constants. Ultimately, simulations on longitudinal control of FAHV demonstrate the control algorithm proposed is superior to conventional quasi‐continuous sliding mode controller in the aspect of convergence accuracy and chattering suppression.

中文翻译：

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改进的连续滑模控制器，用于柔性呼吸高超音速飞行器

针对柔性呼吸超音速飞行器（FAHV），提出了一种改进的连续滑模控制算法，该算法包括非奇异的快速固定时间滑动面（NFFS）和双层自适应连续扭曲到达定律（DACTL）。首先，使用输入/输出反馈线性化方法处理FAHV的非线性控制模型，并以显着的柔性效应建模为未知匹配扰动。其次，通过调整功率指数以加快收敛速度​​，从常规的固定时间滑动表面改进了一种新颖的NFFS。同时，为了避免分数功率项引起的奇异性，在跟踪误差接近零时切换指数收敛滑动面。第三，提出了一种DACTL来实现滑模变量的有限时间收敛，收敛精度更高，震颤更少。双层自适应定律用于根据等效控制概念调整D​​ACTL中的增益，从而自动增强鲁棒性并避免过高估计控制增益。同时，在不了解Lipschitz常数的情况下可以补偿干扰。最终，FAHV的纵向控制仿真表明所提出的控制算法在收敛精度和颤振抑制方面优于传统的准连续滑模控制器。双层自适应定律用于根据等效控制概念调整D​​ACTL中的增益，从而自动增强鲁棒性并避免过高估计控制增益。同时，在不了解Lipschitz常数的情况下可以补偿干扰。最终，FAHV纵向控制的仿真表明，所提出的控制算法在收敛精度和颤振抑制方面优于传统的准连续滑模控制器。双层自适应定律用于基于等效控制概念来调整DACTL中的增益，从而自动增强鲁棒性并避免过高估计控制增益。同时，在不了解Lipschitz常数的情况下可以补偿干扰。最终，FAHV纵向控制的仿真表明，所提出的控制算法在收敛精度和颤振抑制方面优于传统的准连续滑模控制器。