基于无动力成形发放的平流层飞艇区域驻空飞行轨迹优化方法的研究

The stratosphere has become a new hot spot in the military and civil fields for the world nowadays. Compared with other stratospheric air vehicle, the stratospheric airship rises via net buoyancy, thus it costs very little energy resource. Furthermore, the flight of it is under control, so it is able to complete the special mission—staying still in the wind (regional presence). To meet the engineering requirements of stratospheric airship, the idea is proposed from theoretical level in this application: the prediction of unpowered formatted release and the flight trajectory optimization of regional presence are the two key scientific issues to be solved. For the unpowered formatted release, the estimation model for the acting point of net buoyancy is established, based on the structure of the hull with multi cabins and shaped by an arbitrary external generatrix. The evolution laws of the pitch attitude during the formatted climbing phase are studied by using the quasi-static mode, with the consideration of approximate equilibrium of buoyancy and gravity. Thus, the numerical simulation model of release is obtained, which would be great help for the planning of appropriate pressure control exhaust strategy. For the regional presence, the nonequilibrium of buoyancy and gravity caused by alternate day and night flight is discussed. According to the indices of “Plan in 13th Five-Year”, it is presented that the guidance issue “how to play” must be solved first. Thus, the regional presence is transformed to be a trajectory optimization problem with constrained conditions. Then, an optimization algorithm with adaptive capacity is designed via pseudospectral method. From the theoretical level, the research results of this application would solve the complete flight planning problem about the regional presence mission of stratospheric airship. Furthermore, a solid theoretical basis for further engineering practice is offered here.

当前平流层已成为各国在军事、民用领域争夺的热点。相较于其他平流层飞行器，平流层飞艇依靠浮力升空，能耗低，飞行可控，能够完成迎风驻留的飞行任务。基于平流层飞艇的工程化需求，本申请从理论层面提出，无动力成形发放的预测和区域驻空的飞行轨迹优化是两个亟待解决的关键科学问题。针对无动力成形发放，建立外部由任意母线旋成，内部有任意多个气室的艇囊的净浮心估算模型，采用浮重近似平衡的准静态方法对发放俯仰形态进行预测，从而获得升空过程的数值仿真模型，辅助制定合适的压控排气策略。针对区域驻空，考虑长航时昼夜交替飞行导致的浮重不平衡，同时结合“十三五”指标，提出必须先解决“怎么飞”的制导问题，从而将区域驻空转化为一个受约束的轨迹优化问题，基于伪谱法设计具有自适应能力的优化轨迹求解方案。项目的研究成果将从理论层面初步解决平流层飞艇长航时驻空的完整飞行规划问题，为其进一步的工程实践提供坚实的理论研究基础。

在当今的国际背景下，各国在空天领域的角逐显得尤为激烈，一方面是彰显国家发展的综合实力，另一方面是基于大国的空间战略布局。平流层作为空天领域开拓的新领域，其战略地位逐步凸显，已成为各国在军事和民用领域争夺的热点。平流层飞行器主要包括高空气球、平流层飞艇和太阳能无人机。相较于传统的高空气球，平流层飞艇的飞行具有可控性；相较于太阳能无人机，平流层飞艇仅依靠浮力升空，能耗更低、且带载能力更强。因此，在长时期无间断的空间定点侦查中，平流层飞艇具有突出的性能优势，但其技术难度较大，存在着明显的技术瓶颈。从基础工程理论的角度来看，本项目定位了两个亟待解决的关键科学问题：研究外部为任意母线旋成、内部为任意多分气室组合的常规艇囊的净浮心动态估算问题；求解考虑风场环境及动力学热力学耦合的平流层飞艇长航时区域驻留的优化飞行轨迹。针对这两个问题，项目主要从七个方面部署了研究内容：艇囊为双椭球拼接结构的净浮心估算；艇囊为任意母线旋成结构的净浮心估算；区域驻空环境的影响，包括太阳辐射和风场；关于热力学的影响，包括热力学建模和考察空间温度变化的影响；艇囊初始充氦气量的优化，在规定保形的压差下，寻找最优的氦气充气量，优化飞行中固有的结构性能；驻空高度对浮重力的影响分析；区域轨迹规划的关键问题的求解。通过对这些研究内容的深入探索，面向发放和回收，建立了外部由任意母线旋成，内部有任意多个气室的艇囊的净浮心估算模型，利用浮重近似平衡的准静态方法就可以对发放俯仰形态进行有效地预测，从而形成全姿态的动力学、热力学耦合模型；区域驻空飞行轨迹的优化则是通过最优化求解方案将区域驻空转化为一个受约束的轨迹优化问题，从而使其得到解决。项目获得的相关成果在工程中已经得到了一定程度的使用和验证，初步具备了工程化的实际应用价值，有效地支撑了若干大科学问题的探索和实践活动。