基于形状法和伪谱法的小推力借力优化研究

Low-Thrust,Gravity-assist Trajectory Optimization Based on Exponential Sinusoid and Gauss Pseudo-Spectral Method

小推力借力飞行轨道优化是一个多变量多约束的非线性优化问题,根据形状法和伪谱法,提出一种混合优化策略,分为全局优化和局部优化两个阶段进行。在全局优化阶段采用LT-PGA模型,即通过求解形状法小推力Lambert问题,搜索满足约束条件的小推力发射窗口,得到发射、借力和到达时间点。在局部优化阶段采用伪谱法得到推力控制率,用连接点设置解决借力行星处状态量的不连续问题。数值仿真结果表明,改进方法不用事先指定推力开关机序列,优化效率高,为初始设计阶段小推力借力飞行的轨道优化问题提供有益参考。

A novel strategy for low-thrust and gravity-assist optimization was presented in this paper, which is a two-step strategy including global and local optimizations. First, exponential sinusoid low-thrust with powered swing -by model （LT-PGA） was used to perform global optimization to get important mission time points such as launch date, flyby date and arrival date. The results were used as initials in further local optimization using Gauss pseudo- spectral method and the discontinuity during swing-by was handled by linkage settings. Simulations show that the computational requirements are relatively cheaper while optimization is efficient without specifying the thrust on and off sequence in prior. The strategy can be used at the initial design stage to give a quick solution.