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考虑气动参数扰动的再入轨迹快速优化方法

FAST OPTIMIZATION METHOD OF REENTRY TRAJECTORY CONSIDERING AERODYNAMIC PARAMETER PERTURBATION

  • 摘要: 针对传统再入轨迹优化方法收敛速度慢、对初值敏感程度高等的局限性,提出了一种基于序列凸优化的再入轨迹快速求解方法.该方法以倾侧角的变化率作为控制量,改进了现有凸化策略,考虑到抑制数值优化过程中由于数值离散方式带来的锯齿化现象,采用 B 样条曲线离散控制量,同时为避免算法在初始猜想值附近出现伪不可行的问题,增加额外虚拟控制量,通过一种"回溯直线"搜索的方法,提高算法的稳定性、快速性和寻优结果的光滑性.为研究飞行器再入过程中的气动参数扰动问题,采用采样点少、易于实现,计算效率高的广义混沌多项式理论研究方法,建立了基于广义混沌多项式和凸优化相结合的再入轨迹鲁棒优化模型,该模型在优化过程中考虑气动参数扰动对寻优结果的影响作用,避免了传统轨迹与制导律的复杂迭代设计环节,可有效降低优化轨迹对气动参数扰动的敏感程度,在气动参数不确定条件的干扰下,依然可以保证飞行器顺利安全的完成飞行任务.最后,以美国某可重复使用飞行器的再入任务为例,验证了基于序列凸优化的再入轨迹优化方法的快速性以及鲁棒优化模型对气动参数扰动的抗干扰性能力,表明了该方法具有一定的工程应用性.

     

    Abstract: In view of the limitations of the traditional reentry trajectory optimization method, which has slow convergence speed and high sensitivity to initial values, a fast algorithm for reentry trajectory based on sequential convex optimization is proposed. The method takes the change rate of inclination angle as the control variable which improves existing convex strategy and uses B-spline curve to discretize the control variable, which can effectively suppress the sawtooth phenomenon in the process of numerical optimization due to the numerical discrete method. At the same time, to avoid the problem that the algorithm appears pseudo-infeasible near the initial guess value, additional virtual control and a "backtracking straight line" search method are added to improve the stability of the algorithm, these can improve the stability, rapidity and smoothness of the algorithm. In order to study the aerodynamic parameter perturbation in the reentry process of aircraft, a generalized polynomial chaotic theory research method with few sampling points, easy implementation and high computational efficiency is proposed. A robust optimization model of reentry trajectory based on the combination of generalized polynomial chaos and convex optimization is established. The model considers the effect of aerodynamic parameter disturbance on the optimization results during the optimization process, which can avoid the complex iterative design of conventional trajectory and guidance law. What's more, it can effectively reduce the sensitivity of optimal trajectory to aerodynamic parameter perturbation, and under the disturbance of uncertain aerodynamic parameters, which still can ensure the safety of the aircraft smooth completion of the mission. At the end,taking the reentry mission of a reusable aircraft in the United States as an example, the rapidity of reentry trajectory optimization method based on sequence convex optimization and the anti-interference ability of robust optimization model to aerodynamic parameter perturbation are verified and it shows that this method has certain engineering application.

     

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