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研究嫦娥三号软着陆轨道设计与控制策略。针对问题一,通过题目所给出的数据,根据嫦娥三号着陆准备时绕行轨道是椭圆轨道,以开普勒三大定律为基础,有限单元离散化,确定近月点与远月点嫦娥三号绕行的速度及方向,再根据题目所给着陆点,建立空间直角坐标系来确定近月点与远月点位置坐标。最后求得如下数据:近月点速度为1.69km/s,远月点速度为1.61km/s速度的方向均是沿月球自转方向。针对问题二采用约束变换法,有限单元离散化,从燃耗优化,轨迹优化两个方面,粗略地提出了嫦娥三号软着陆轨道的优化方案并应用matlab软件最终确定了着陆轨迹。最后得出最优燃耗为823.77kg。针对问题三,进行了误差分析与敏感性分析,通过建立影响月球软着陆主制动段制导精度的误差模型,并运用误差敏感系数矩阵对所设计制导律的制导误差做出了分析。结果表明:与初始位置偏差相比,初始速度偏差对终端各状态的影响要大;位置、速度测量误差分别只对本轴终端位置速度影响较大;制导律对刻度因素误差最敏感。
Research on the design and control strategy of Chang’e III soft landing trajectory. Aiming at the problem 1, according to the data given by the title, the orbit of the orbit of the Chang’e III landing is an elliptical orbit. Based on the Kepler’s three major laws, the discretization of the finite element is performed to determine the distance between the near point and the far- Third, the speed and direction of the detour, and then according to the subject to the landing point, the establishment of space Cartesian coordinate system to determine the coordinates of the near-month and far-month point coordinates. In the end, the following data are obtained: the point velocity in recent months is 1.69 km / s and the velocity in the far moon point is 1.61 km / s in the direction of rotation of the moon. In order to solve the problem two, the constrained transformation method and finite element discretization are used. From the aspects of fuel consumption optimization and trajectory optimization, the optimization scheme of Chang’e III soft landing orbit is proposed roughly and the landing trajectory is finally determined by matlab software. Finally, the best fuel consumption was 823.77kg. For the third problem, the error analysis and the sensitivity analysis are carried out. By establishing the error model that affects the guidance accuracy of the main braking stage of the lunar soft landing, the guidance error of the designed guidance law is analyzed by using the error sensitivity coefficient matrix. The results show that compared with the initial position deviation, the initial velocity deviation has greater influence on each state of the terminal. The position and velocity measurement errors respectively affect only the position velocity of the local axis. The guidance law is most sensitive to the scale factor error.