火箭着陆段能量管理与轨迹优化技术

Energy management and trajectory optimization technology for rocket landing

垂直回收火箭返回着陆段发动机推力与气动力高度耦合,火箭着陆可行性与安全性不仅取决于轨迹终端位置、速度和姿态偏差,还取决于初始姿态偏差与着陆能量的控制能力。针对带有发动机起动段与喷流影响下气动力变化的复杂动态模型轨迹规划问题,通过在起动段采用多项式制导方法以及在推力节流调整段采用解析初值-序列凸优化方法进行分段轨迹在线规划;为消除分段求解模型差异带来的切换姿态角跳变,利用五次多项式形式推导得到含初始姿态角约束的解析初值参考剖面;然后通过对推力角与轨迹倾斜角度约束的动态调整,以及引入偏差松弛项,将终端质量约束添加到优化性能指标函数中,利用序列凸化迭代方法完成对具有终端位置、速度、姿态和指定质量约束的优化问题求解。结果表明:所提方法相较于传统多项式或凸优化方法,在约束数量与精度指标方面具有优势,在组合偏差条件下能够满足准确的终端位置、速度和终端质量约束,终端姿态角偏差<1.5°,同时在线规划平均耗时<1 s,具有较好的工程应用前景,可为我国新一代可重复使用载人运载火箭的相关研制工作提供一定的参考。

The engine thrust and aerodynamic forces are highly coupled in vertical recovery rocket landing,and the rocket feasibility and safety depend on not only the trajectory terminal position,velocity and attitude deviation,but also the initial attitude deviation and the control accuracy of the landing energy.Aiming at the complex dynamic model trajectory planning with aerodynamic changes under the influence of the engine starting section and jet stream,the segmented trajectory online planning is conducted by adopting the polynomial guidance method in the starting section and the analytical initial value-sequential convex optimization method in the thrust throttling adjustment section.To eliminate the jumps of the switching attitude angle caused by the difference of segmented solving models,a quintuple polynomial form was used to obtain the analytical initial value reference profile with the constraints of the initial attitude angle.Then,through the dynamic adjustment of the thrust angle and trajectory tilt angle constraints as well as the introduction of a deviation relaxation term,the terminal mass constraint was added to the optimization performance index function,and the optimization problem with constraints on the terminal position,velocity,attitude,and specified mass was completed using the sequence-convex iterative method.The results show that the proposed method has advantages in accuracy index and number of constraints compared with the traditional polynomial or convex optimization methods.Capable of achieving accurate terminal position,velocity and terminal mass constraints under the combination of deviation conditions,with the terminal attitude angle deviation less than 1.5°,and the average time consumed for online planning less than 1 s,it has a good engineering application prospect and can provide reference for the development of China’s new generation of reusable manned launch vehicles.