This paper conducts a comparison study of constrained powered descent guidance laws for planetary pin-point landing from the viewpoints of guidance performance and algorithm structure. All considered algorithms are reformulated to incorporate the critical elements of the powered descent problem, such as the free flight time, thrust limitation and terrain constraint. With these requirements to meet, the performance of guidance laws is evaluated and compared via simulations. Specifically, the nominal landing simulation verifies the guidance accuracy, fuel consumption, and real-time performance, as well as the hazard avoidance capability. Meanwhile, the robustness of guidance laws is evaluated by the Monte Carlo simulation, and the performance difference in final landing dispersion is interpreted by analyzing the algorithm structure and characteristics. Lastly, the discussion on practicability indicates the promise of optimization-based algorithms in future planetary landing missions.

本文从制导性能和算法结构的角度对行星精确着陆的约束动力下降制导律进行了比较研究。所有考虑的算法都经过重新制定，以纳入动力下降问题的关键要素，例如自由飞行时间、推力限制和地形约束。满足这些要求后，通过模拟评估和比较制导律的性能。具体来说，标称着陆模拟验证了制导精度、油耗和实时性能，以及避险能力。同时，通过蒙特卡罗模拟评估制导律的鲁棒性，并通过分析算法结构和特点来解释最终着陆分散的性能差异。最后，关于实用性的讨论表明了基于优化的算法在未来行星着陆任务中的前景。