Journal of Astronautics ›› 2021, Vol. 42 ›› Issue (10): 1246-1256.doi: 10.3873/j.issn.1000-1328.2021.10.006

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A Guidance Algorithm for Pinpoint Soft Landing of Economical Lunar Lander

GAO Feng, JING Wu xing, GAO Chang sheng, LI Zhi gang, ZHONG Wei   

  1. 1. Department of Aerospace Engineering, Harbin Institute of Technology, Harbin 150001, China;2. Aerospace System Engineering Shanghai, Shanghai 201109, China

  • Received:2020-10-13 Revised:2021-03-08 Online:2021-10-15 Published:2021-10-15

Abstract: Considering the characteristics of the motors and terminal state constraints, the guidance algorithm for pinpoint soft landing of an economical lunar lander is studied in this paper. Firstly, considering the establishment of future lunar communications network and the utilization of resources, a strategy of phasing is studied when the lander travels in the lunar polar orbits, which can cover all lunar landing sites. Then the dynamics model of the main descent phase is established in the NED frame. The motion of the lander is divided into the longitudinal plane motion and lateral motion, and their online closed loop guidance algorithms are designed respectively. The longitudinal plane motion adopts an improved explicit guidance, and a fire angle correction strategy which satisfies the terminal course position constraint is designed based on the finite thrust theory and the error propagation characteristics of the main descent phase. For the lateral motion control, the guidance instructions are given based on the ZEM/ZEV optimal feedback guidance law, then the pulse control laws are calculated from the continuous laws with PWPF modulation. The simulation results show that the guidance algorithm is able to satisfy all terminal state constraints with good performance, and is easily implemented in engineering.

Key words: Economical lunar lander, Improved explicit guidance, Fire angle correction, ZEM/ZEV, PWPF

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