可重复使用运载器再入轨迹次实时优化

Near real-time optimization for reentry trajectory of RLV

新一代可重复使用运载器RLV(Reusable Launch Vehicle)再入时应具备自主导航的能力,其实现的关键是用机载计算机近实时或实时地生成一条满足各种约束条件的再入轨迹.根据RLV再入的特点,引入了新的假设,对再入轨迹方程进行简化处理,优化难度降低,工作量减少.另外引入次优化轨迹的概念,对控制量(迎角和滚转角)的优化分两步进行,每步只对当中一个控制量进行优化.这样处理能在很大程度上加快算法的收敛速度.仿真结果表明,只需10s左右的时间就能产生一条满足终端约束条件、控制量约束条件和加热率约束条件的次优化轨迹.其结果具有较好的工程应用价值.

Determining how to find the best controls of a re-entering reusable launch vehicle （RLV） so that it is able to safely reach the terminal area energy management （TAEM） involving the solution of a twopoint 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 computation time by most of algorithms. But it＇s very necessary to find the optimal controls quickly for some flight tasks. Traditional trajectory optimal algorithm can not shoulder this fast optimization task. In that work, a new hypothesis was introduced according to the features of constrained three-dimensional reentry trajectory of RLV. The set of dynamics and kinematics equations of motion was divided into two sets and only one set equations participate in the optimization iteration algorithm, which improves the efficiency of optimization greatly. Then the methods of multipliers was used to deal with the terminal constraints. Later the conjugate-gradient method was applied to evaluate the optimal reentry trajectory. Successful results show the algorithm is able to generate a feasible reentry trajectory in 10 s on the desktop computer.