基于蒙特卡洛树搜索的机载雷达编队策略优化

多机雷达协同探测是飞机协同作战研究的重要内容,编队策略影响着多机雷达协同探测的探测效能针对机载雷达编队策略的优化,基于部分可观察马尔可夫决策过程(POMDP)模型描述了编队策略优化问题,提出了一种基于蒙特卡洛树搜索(MCTS)的最优策略求解方法。以对敌方目标的探测性能为指标,将该方法与多种其他编队方法的结果进行了比较。试验结果表明,该方法很好地平衡了 MCTS 中利用与探索的关系,可以在规模较大的搜索空间内有效完成编队策略优化,在编队探测能力提升方面展示出了比其它方法更加优越的性能。     

SiP陶瓷芯片水汽含量控制工艺方法研究

结合宇航级陶瓷封装芯片的特点和水汽控制要求,对SiP陶瓷封装工艺进行了研究,分析了陶瓷封装过程中产生水汽的各个因素,优化了封装生产工艺流程,增加了预烘转运过程下厂监制,保证了转运时间的工艺过程管控,通过试验验证了管控措施的有效性.     

斜爆轰波并行数值模拟的化学加速算法性能研究

考虑基元反应条件下的爆轰波精细结构的数值模拟计算量巨大,发展高精度和高效率的计算方法十分必要.以Ma=7的H2/O2/N2预混气来流形成的斜爆轰波为数值模拟对象,研究了一种基于并行计算架构的用于加速化学反应计算的建表算法的计算性能,考察了不同建表策略,即TP(Transposed processing)策略和PLP(P...     

Experimental study on flow excursion instability of supercritical hydrocarbon fuel in scramjet regenerative cooling parallel channels

Flow instability of supercritical hydrocarbon fuel is a crucial issue in scramjet regenerative cooling structure. In this study, flow excursion instability and flow distribution in parallel tubes were experimentally studied for supercritical fluids. Two types of flow excursion occur in a single tube. Type I and Type II excursions, and they are corresponding to decreasing and increasing flow rate respectively. They can trigger flow maldistribution between parallel tubes and the hysteresis phenomenon of flow distribution. The effects of system parameters, including inlet temperature, system pressure, and heat flux, on flow distribution were analyzed. In addition, the relationship between flow excursion and the pseudo-critical interval proposed in the literature was established according to the heated tube outlet temperature at the onset of flow instability. Finally, the flow excursion instability boundary was obtained using two dimensionless parameters. These experimental results can provide helpful insight on the mechanism of Scramjet regenerative cooling.     

Derivation and validation of a similarity law for free-flight wind tunnel tests of parallel stage separation

Aiming at the safety problem of the stage separation of parallel reusable high-speed air vehicles, this paper studies the unsteady test method and focuses on deriving a similarity law of parallel stage separation free-flight wind tunnel tests. The new similarity law considers the influences of aerodynamic force and gravity on the motions of the two stages, as well as the influence of aerodynamic interference between the two stages on each other’s motion. From the perspective of multi-angle physical equations, the conditions to ensure that the two-stage separation trajectory of a wind tunnel test is similar to that of a real air vehicle are derived innovatively, so as to ensure the authenticity and credibility of wind tunnel test results. The similarity law is verified by an HIFiRE-5 air vehicle, and the separation trajectories of wind tunnel tests and the real air vehicle are obtained by numerical simulation. The research shows that the similarity law derived in this paper can ensure that wind tunnel free-flight tests have the ability to predict the two-stage separation characteristics of real parallel vehicles. By analyzing the separation trajectory curve of the typical state, it is found that the new method can ensure that the trajectory error of a wind tunnel test does not exceed 1%, which indicates that this method is credible. The establishment of the new method lays the foundation for subsequent wind tunnel tests and provides support for research on the safety of the stage separation of parallel reusable air vehicles.     

固体火箭飞行静载荷计算的偏差使用方法优化

新型固体火箭对提升运载效率的需求日益强烈,由此发展出一些以提升载荷设计精度为目标的载荷优化方法,可有效实现结构的减载减质。现有优化方法仅考虑单项偏差,未考虑各项偏差间的匹配性和传递过程的合理性,很大程度上限制了载荷设计精度的进一步提升。梳理和分析了载荷计算过程涉及的多项参数偏差,提炼出原始偏差和过程偏差的概念,指出了传统方法在偏差使用及传递过程中的不合理。在此基础上,充分结合新型固体火箭的研制特点,改进了偏差的使用方法,降低了过程偏差对载荷计算精度的影响。结果表明该方法可有效提高载荷设计精度、准确性和效率。     

碳纤维增强树脂基复合材料壳体相贯线孔加工工艺

介绍一种用于碳纤维复合材料大直径不垂直相贯线孔加工方法。综合考虑了加工温度,加工质

量,排屑及加工效率等问题。结果表明,采用一种简易的加工工装保证了孔的尺寸及位置精度,使相贯线孔能

够一次性加工完成。通过对传统磨头的工艺改进解决了排屑及散热问题,并提高了复合材料的表面加工质量。

     

Conceptual design and analysis of legged landers with orientation capability

The lander with orientation capability is of fundamental importance for the “Returning” mission because its body can be the base with a suitable launching angle for the ascender lifting off. This paper proposes the conceptual design and verification of Landers with Orientation Capability (LOCs). Firstly, the topological composition of the lander is analyzed and expressed in the form of Lie group, which provides the fundamental principle for the type synthesis of LOCs. Then, the type synthesis approach for designing LOCs is proposed, which includes designing the Equivalent Parallel Mechanism (EPM) and the auxiliary limbs. Numerous mechanisms of LOCs with two-dimensional rotational motions are obtained based on the type synthesis approach by developing and combining the EPMs and auxiliary limbs. Afterward, kinematics and Jacobian matrix of a typical legged lander are developed, the workspace is analyzed, singularity configurations are analyzed based on the wrench graph method, and finally, the orientation capability is analyzed. The pitch and yaw angle reach 17.5°, considering the permissible range of joints. The proposed types of LOCs offer potential candidate for the “Returning” mission of the exploration mission.     

Enhancement on parallel unstructured overset grid method for complex aerospace engineering applications

In the present study, an efficient overset grid method by means of parallel implicit hole-cutting is proposed for the sake of simulating unsteady flows in aerospace engineering involving multiple bodies in relative movement. In view of the degraded computational efficiency and robustness for conventional overset grid assembly, several innovative techniques are developed within the overset grid assembly process, viz., a bookkeeping alternative digital tree method to speed up the donor-cell search...     

前驱体浸渍裂解过程中SiC/SiC复合材料微观工艺应力模拟研究

前驱体浸渍裂解工艺（PIP）是SiC/SiC复合材料的一种近净成形制备方法，但前驱体裂解过程中产生的应力阻碍了该工艺的产业化应用。本文构建了一种化学-力学耦合模型来研究前驱体裂解过程中应力的产生和演化机理。首先以反应动力学模型描述了前驱体的裂解过程；其次基于三相球模型建立了一个解析模型计算基体的均匀化力学性质；最后结合上述模型构建了有限元模型，在微观尺度模拟计算了代表性体积单胞（RVC）内的工艺应力演变。结果表明：基体在贫基体的界面处承受显著的环向拉伸应力；对于由纯前驱体组成的基体，基体内的工艺应力主要是由裂解过程引起的化学收缩导致的，受温度引起的热膨胀影响较小；随着PIP循环次数的增加，化学收缩和热膨胀的角色发生互换。