月球软着陆轨道快速优化

Fast Optimization of Trajectory for Lunar Soft Landing

月球软着陆轨道是登月飞行器下降到月球表面轨道中很重要一段的轨道,为了实现飞行器自主软着陆,需要进行快速轨道优化设计。文中根据软着陆轨道的特征和优化算法的特点,对软着陆轨道状态方程做合理的简化处理,优化计算量减少,且更适合优化数值解法求解。在此基础上,使用乘子法处理软着陆终端约束条件,然后利用共轭梯度法求解软着陆轨道。在不同初始条件和终端约束条件下,计算机时小于3秒。仿真结果验证该算法具有收敛速度快、对初始控制量不敏感等优点,易于工程实现。

Determining how to find the best controls of the lunar landing vehicle so that it is able to safely reach surface of the moon involves the solution of a two-point boundary value problem.This problem,which is considered to be difficult,is traditionally solved on the ground prior to flight.The optimal controls are found regardless of computing time by using most of algorithms.However,it＇s crucial to find the optimal controls in real-time for some landing tasks.Traditional trajectory optimal algorithm can not perform this fast optimization task.In this work,a new hypothesis is introduced according to the distinguished features of lunar and the character of soft landing trajectory.The set of dynamics and kinematics equations of motion is simplified,which improves the efficiency of optimization greatly.Then the methods of multipliers are used to deal with the terminal constraints.Later the Conjugate-Gradient Method is applied to evaluate the soft landing trajectory.Successful results show that the algorithm is able to generate a feasible soft landing trajectory of about 600 seconds flight time in 3 seconds on the desktop computer.