火箭返回制导动力着陆段的自适应启动方法

针对重复使用火箭垂直返回着陆问题，提出了一种燃料最优的动力着陆段自适应启动方法。首先，将燃料最优启动点对应的动力着陆轨迹的推力剖面和攻角剖面描述为解析的形式，该解析形式中攻角剖面由状态量唯一确定，推力剖面仅含一个待定参数。随后，通过预测具有上述解析剖面形式的轨迹判断是否启动动力着陆。计算中引入松弛终端位置约束的策略求解推力剖面待定参数，由终端位置约束判断是否满足燃料最优启动条件。上述策略将燃料最优启动条件的判断问题简化为单一变量求解问题，实现了该问题的快速求解。仿真结果表明，该方法得到的启动点与数值优化方法得到的燃料最优启动点接近，且求解过程稳定、计算效率高。

Adaptive Powered Descent Initiation of Rocket Return Guidance

To solve the problem of vertical return landing of reusable rocket, an adaptive fuel optimal powered descent initiation(PDI) approach is proposed. Firstly, two analytical forms are used to describe the profiles of the thrust and the angle of attack for the fuel optimal powered descent trajectory of the fuel optimal PDI state. In these forms, the angle of attack profile is determined by the current state, the thrust profile only depends on one unknown variable. Secondly, the PDI state is determined by predicting the powered descent trajectory with the above analytical profiles. The terminal position constraint is relaxed to solve the unknown variable of the thrust profile. The predicted trajectory meets the terminal position constraint means that the current state is close to the fuel optimal PDI state. The above strategy simplifies the problem of determining the fuel optimal PDI state into the problem of solving the single unknown variable, so as to solve the problem quickly. Finally, numerical simulations demonstrate the proposed approach is numerically stable and efficient, and achieves comparable fuel efficiency with numerical optimization approaches.