改进的探月返回飞船再入数值预测校正制导方法

Improved numerical predictor-corrector guidance for lunar return capsule

摘要:

为减少探月返回飞船再入数值预测校正制导方法在跳跃段倾侧角的偏转频率、实现过载的有效抑制，采用搜索跳跃段的倾侧角偏转能量点和末段阻力加速度反馈补偿的方法，提出了改进的数值预测校正制导方法.首先，用割线法搜索倾侧角偏转能量点，使得飞船在跳跃段只进行一次偏转即可实现落点精度要求; 然后，根据指数大气假设，得到阻力加速度的导数，并根据过载约束定义参考阻力加速度；最后，采用阻力加速度及其导数与参考阻力加速度及其导数的误差对倾侧角的大小进行反馈补偿，抑制末段轨迹的过载.实验结果表明，该方法倾侧角偏转次数少，过载抑制能力强，鲁棒性好，能够有效解决现有方法存在的跳跃段倾侧角偏转频率高，末段过载抑制能力差的问题.

Abstract:

To decrease the bank angle reversal frequency in the skip phase and suppress the aerodynamic load effectively in the final phase of the numerical predictor-corrector guidance for lunar return capsule, an improved guidance scheme is proposed by searching for the energy point of the only one bank reversal in the skip phase and compensating the guidance command with drag acceleration feedback in the final phase. Firstly, the secant method is used to search for the bank angle reversal energy point, so that the bank angle is just reversed once in the skip phase. Secondly, based on the exponential atmosphere assumption, the derivative of the drag acceleration is obtained, and a reference drag acceleration profile is determined according to the load constraint. Finally, the errors of the drag acceleration and its derivative between the reference profiles and the actual profiles are used to compensate the basic bank angle magnitude in the final phase to relieve the aerodynamic load. The testing results demonstrate that the proposed algorithm can reduce the bank angle reversal frequency in the skip phase and suppress the aerodynamic load effectively with strong robustness, which show that the problems have been successfully solved and the scheme can provide a reference for practical guidance system design.