The recently developed flexible lander offers a potential option for future asteroid landing missions due to its advantages in suppression of rebound and overturning. The strong nonlinear dynamics and control constraints of the flexible lander hinder the online implementation of optimal attitude feedback control. To generate the optimal attitude control rapidly, a constrained inhomogeneous approximating sequence of Riccati equations (CI-ASRE) method is proposed. The saturation function is firstly constructed to incorporate control magnitude constraints into dynamics so that the constraints can be analytically handled. Subsequently, to avoid singularity, a partial factorization strategy is proposed to convert the constrained dynamics into two parts, a pseudolinear term and an inhomogeneous term. This factorization enables the nonlinear problem to be expressed as the limit of a sequence of inhomogeneous linear quadratic problems while avoiding local linearization. At last, the analytical CI-ASRE is newly derived to iteratively solve these problems to rapidly obtain optimal feedback control. The computational simplicity and effectiveness of the CI-ASRE method overcome difficulties of optimal attitude control problems of the flexible lander associated with control constraints, strong nonlinearity, and online feedback control generation. The effectiveness of the proposed method for the flexible lander is verified using a landing scenario on asteroid 433 Eros.

中文翻译：

---

柔性着陆器登陆小行星的最佳姿态控制


最近开发的柔性着陆器因其在抑制反弹和倾覆方面的优势，为未来小行星着陆任务提供了潜在的选择。柔性着陆器强非线性动力学和控制约束阻碍了最优姿态反馈控制的在线实现。为了快速生成最优姿态控制，提出了一种约束非齐次逼近Riccati方程序列（CI-ASRE）方法。首先构造饱和函数，将控制幅度约束纳入动力学中，以便可以分析处理约束。随后，为了避免奇异性，提出了部分分解策略，将约束动力学转换为两部分：伪线性项和非齐次项。这种因式分解使非线性问题能够表示为一系列非齐次线性二次问题的极限，同时避免局部线性化。最后，新推导了解析式CI-ASRE来迭代解决这些问题，以快速获得最优反馈控制。 CI-ASRE方法的计算简单性和有效性克服了与控制约束、强非线性和在线反馈控制生成相关的柔性着陆器最优姿态控制问题的困难。使用 433 Eros 小行星上的着陆场景验证了所提出的灵活着陆器方法的有效性。