A Study Of The Guidance And Control Strategy In Lunar Soft-landing

The study is concerned the mission of landing in the polar regions of lunar which has complex terrain. In this paper, guidance and control (G&C) methods of soft landing phase for lunar probe is investigated. The main contents is as followed:Firstly, the mode and process of soft landing are discussed based on analysis of lunar soft landing missions that have been successfully carried out. The requirements for GNC system and normal G&C strategies are also discussed.Secondly, considering the current space technology conditions in China, an explicit guidance method for powered descending phase is studied to minimize the fuel consumption. An analysis of the performance by numerical simulation results shows this method used for powered descending phase is prior to most of the others.Thirdly, to ensure a safety soft-landing in Polar Regions, the conventional Gravity-turn strategy is analyzed and improved. Tacking guidance strategy is studied using nonlinear transformations. By following the defined velocity vs. slant-range profile the Lander's velocity magnitude can be shaped. This guidance strategy can compensate for the limitations in the Gravity-Turn. And then, potential function method is used for shaping the terminal descent path in order to avoid the large obstructions on the lunar surface. Its stability can be proved by Lyapunov theory. In principal, it can lead a soft landing on complex terrains autonomously and safely.Finally, adopting guidance and control law, the process of soft landing descending is validated by numerical simulation. The numerical simulation demonstrates that the guidance and control law is in real-time. And the quantity of calculation is less than other laws. In theory, it can lead a soft landing on complex terrains autonomously and safely.