The orbit design and control strategy model of Chang’e-3 in the main reduction process

Abstract

On December 14, 2013, Chang'e-3 set down on the moon, making China the third country in the world to set a soft landing with a lunar probe. It is a great honor for us Chinese, but also a great challenge for the project staff through the whole process. Of the characteristics of automatic navigation control, the moon landing stage is considered to be the most important test. In this paper, the dynamic model based on the uniform sphere three-dimensional soft landing model is established to searching Chang'e-3’s optimal trajectory in the main reduction process along the moon landing stage. Also, the computer simulation method and the exhaustive method are employed. Compared with the searched video information, the accuracy of the results is verified. Introduction Chang'e-3 launched on December 12, 2013 and successfully landed on the moon two days later. It is the first time for china to send a spacecraft land on the surface of an extraterrestrial body and conduct surveys on the moon. Furthermore, the success makes China the third country to carry out such a rover mission after the United States and former Soviet Union. For there is no air on the moon, parachute is unavailable. Chang'e-3 has to rely on a variable thrust engine, to complete the soft landing task in the mid-course corrections, the braking at perilune, the powered lowering, and the hovering period. At this stage, the measurement and control technology can not keep up with the operation of the satellite. As a consequence, Chang'e-3, armed with the program set in advance, depend entirely on autonomous navigation control, reducing the height, determining the landing site, achieving the soft landing and a series of key actions. In this paper, the dynamic model based on the uniform sphere three-dimensional soft landing model is established to solve Chang'e-3’s optimal trajectory in the main reduction section. The optimization goal is the fuel consumption, and is transferred to the seeking for the shortest time, for the largest thrust remains the same in the main reduction stage. Then, the exhaustive method list three kinds of movements: constant horizontal thrust, constant speed reverse thrust and constant speed reverse thrust after constant speed reverse resultant force., and only to find that just the last one state meet the key position after simulation. Then, the computer simulation method is employed, and the movement of the main reduction process is given. Compared with the searched video information, the accuracy of the results is verified. The dynamic model based on the uniform sphere three-dimensional soft landing model [2]  Symbols and definitions Symbols Definitions 5th International Conference on Information Engineering for Mechanics and Materials (ICIMM 2015) © 2015. The authors Published by Atlantis Press 1453 max a the largest horizontal reverse acceleration min t the shortest time that the horizontal speed reduce to 0 min h the land’s vertical landing altitude in the process μm the moon's gravitational constant I the specific impulse of propulsion system G the acceleration of gravity of the earth's surface F a brake thrust acceleration m a the moon's gravitational acceleration φ the main reduction period of latitude deflection angle  Model building 1) Establish the coordinate system The moon heart inertial reference coordinate system OXYZ: the origin of the coordinate system 0 is located in the heart. The Z axis directs from the moon heart to the initial landing point, while the X axis in lunar orbit plane points in the heading direction. The Y axis constitutes the rectangular coordinate system with the and X axis and Z axis, which is shown in figure 1. Descending track reference coordinate system oxyz: origin 0 is located in the lander centroid, and the y axis directs from the moon heart to lander centroid, while the x axis in the local water points to the lander's heading direction. The z axis constitutes the rectangular coordinate system with the x axis and y axis. The two thrust Angle between the constant thrust F and xyz coordinate system oxyz are thrust bearing φ and thrust angle θ respectively. It is the positive while the thrust bearing rotates around the positive x axis and the thrust angle rotates around the negative x axis. As shown in figure 2. Fig1.The moon heart inertial reference coordinate system