Optimization and verification of free flight separation similarity law in high-speed wind tunnel

Based on the similarity of separation time, a similarity law optimization method for high-speed weapon delivery test is derived. The typical separation state under wind load is simulated by the numerical method. The real separation data of aircraft, separation data of previous test methods, separation data of ideal wind tunnel test of previous methods, and simulation data of the proposed optimization method are obtained. A comparison of the data shows that the method proposed can improve the performance of tracking. Similarity law optimization starts with the development of motion equations and dynamic equations in the windless state to address the problems of mismatching between vertical and horizontal displacement, and to address the problems of separation trajectory distortion caused by insufficient gravity acceleration of the scaling model of existing light model. The ejection velocity of the model is taken as a factor/vector, and is adjusted reasonably to compensate the linear displacement insufficiency caused by the insufficient vertical acceleration of the light model method, so as to ensure the matching of the vertical and horizontal displacement of the projectile, and to improve the consistency between the test results of high-speed projection and the actual separation trajectory. The optimized similarity law is applicable to many existing free-throwing modes of high-speed wind tunnels. The optimized similarity law is not affected by the ejection velocity and hanging mode of the projectile. The optimized similarity law is suitable not only for the launching of the buried ammunition compartment and external stores, but also for the test design of projectile launching and gravity separation.     

基于拓扑优化和形状优化的桨叶结构设计

直升机旋翼桨叶剖面结构设计是研究旋翼动力学设计的基础。提出一种联合拓扑优化和形状优化的 两级优化设计方法,可用于桨叶剖面结构的设计。第一级优化以变密度法(SIMP)作为拓扑优化的材料插值方 法,以桨叶体积最小化为设计目标,约束桨叶节点位移和应力,建立桨叶的拓扑优化求解模型;第二级优化以重 构的桨叶模型为基础开展形状优化,降低局部应力集中以及找到合理的边界节点位置。对优化后的模型进行 有限元分析,结果表明:通过拓扑优化和形状优化的两级优化,能够得到满足强度和稳定性要求的结构布局,为 桨叶结构设计提供指导方案。     

A review of topology optimization for additive manufacturing: Status and challenges

Topology optimization was developed as an advanced structural design methodology to generate innovative lightweight and high-performance configurations that are difficult to obtain with conventional ideas. Additive manufacturing is an advanced manufacturing technique building as-designed structures via layer-by-layer joining material, providing an alternative pattern for complex components. The integration of topology optimization and additive manufacturing can make the most of their advantages and potentials, and has wide application prospects in modern manufacturing. This article reviews the main content and applications of the research on the integration of topology optimization and additive manufacturing in recent years, including multi-scale or hierarchical structural optimization design and topology optimization considering additive manufacturing constraints. Meanwhile, some challenges of structural design approaches for additive manufacturing are discussed, such as the performance characterization and scale effects of additively manufactured lattice structures, the anisotropy and fatigue performance of additively manufactured material, and additively manufactured functionally graded material issues, etc. It is shown that in the research of topology optimization for additive manufacturing, the integration of material, structure, process and performance is important to pursue high-performance, multi-functional and lightweight production. This article provides a reference for further related research and aerospace applications.     

最小数据丢失量的地月中继卫星任务调度研究

月球背面的探测器必须依靠地月中继卫星进行数据传输与通信。地月中继任务包括实时性任务和延迟容忍类任务,如数传任务。当探测器等待传输的数据量超出用户存储容量时,延迟容忍类任务会由于探测器本地存储资源不足和地月中继卫星天线资源受限而无法完成,导致任务数据丢失,所以需要设计一种合理的地月中继任务调度策略,提高地月中继卫星的资源利用率,减少数据的丢失。对地月中继卫星任务调度进行了研究,在分析地月中继卫星数传任务的特点及用户的存储限制的基础上,以最小化数据丢失量为优化目标,建立了地月中继卫星任务调度模型,并设计了一种基于离散烟花算法（DFWA）的地月中继卫星任务调度算法。仿真数据分析表明,基于离散烟花算法的地月中继卫星任务调度算法在求解结果上优于遗传算法,是一种合理、有效的调度方法。     

eLoran系统ASF网格应用算法研究

ASF网格是提高增强型罗兰（Enhanced Long Range Navigation,eLoran）系统精度的重要方法。根据所在网格四个顶点的附加二次时延（Added Secondary Factor,ASF）值通过网格应用算法得到待测试点的ASF值,一定程度上比公式计算的ASF值更准确。在计算过程中,用户四个顶点ASF值的测量误差会传递给用户,同时内插算法本身也会引入误差,此时内插算法的选择尤为重要。本文通过仿真、分析比较几种常用的内插算法,得出结论：反距离插值算法引入的误差最大,双线应插值算法引入的误差最小,而且误差呈现一定层次感,网格从内到外误差逐渐减小。     

多变量全局寻优与智能优化在星座组网中的应用

顶层任务规划通常与星座组网紧密结合,小卫星分散灵活的特性尤其适用于星群规模化在轨运行。针对热点区域覆盖和全球覆盖的不同任务需求,提出了对构型多变量进行全局寻优和利用智能优化技术进行星座构型优化的方法,两种优化方法可分别获得小规模星群最优效能与超大型星群的较优效能。优化方法不受轨道类型和任务目标分布的约束,具有良好的鲁棒性。     

W波段UAV MISAR实时成像运动补偿方法

建立了实时成像正侧视合成孔径雷达(SAR)运动误差模型,采用了一种基于惯导和相位梯度自聚焦(PGA)运动误差估计的中心波束平面运动补偿算法。该算法对回波包络和相位进行分开补偿,利用惯导数据把带有运动误差的回波包络拉直,再利用相位梯度自聚焦算法对回波进行相位误差估计并补偿。针对实时成像的时间少、运算量大、运算资源受限等特点,该算法取消了距离徙动校正的步骤,将运动误差矢量在斜距平面投影并完成包络校正和相位误差估计。该方法运算量小,同时能满足分辨率要求。仿真结果表明:该方法能够得到质量较高的SAR图像。     

100 kWe级空间快堆核电源系统仿真平台开发与应用

空间核反应堆电源作为一种具有竞争力的空间电源方案,正逐渐受到关注及应用。本文针对一个100 kWe级锂冷快堆耦合布雷顿循环的空间堆核动力系统方案,修改了RELAP5程序中的物性程序、换热模型,程序中的中子动力学模块使用蒙特卡洛方法计算快堆物理参数与堆芯控制调节参数,由此集成并建立一个空间快堆核动力系统综合仿真平台,应用该平台对100 kWe级空间堆核动力系统进行了稳态模拟与事故分析。结果表明:在瞬态发生后系统各参数变化符合预期,验证了各部件及控制系统的功能性及有效性;同时,还初步进行了仿真平台用于100 kWe级空间反应堆核动力系统设备的设计优化的实践,为空间快堆设计与安全分析提供了技术储备。     

一种中心型间断有限元MMALE方法

针对多介质可压缩流体动力学问题,提出了一种单元中心型二维MMALE(Multi-Material Arbitrary Lagrangian-Eulerian)方法.在拉氏步,流体力学方程组采用中心型间断有限元方法求解.对于混合网格,采用Tipton压力松弛模型更新物理量,用等参坐标法更新物质中心点坐标.界面重构采用一种...     

Hypersonic reentry trajectory planning by using hybrid fractional-order particle swarm optimization and gravitational search algorithm

This paper proposes a novel hybrid algorithm called Fractional-order Particle Swarm optimization Gravitational Search Algorithm (FPSOGSA) and applies it to the trajectory planning of the hypersonic lifting reentry flight vehicles. The proposed method is used to calculate the control profiles to achieve the two objectives, namely a smoother trajectory and enforcement of the path constraints with terminal accuracy. The smoothness of the trajectory is achieved by scheduling the bank angle with the aid of a modified scheme known as a Quasi-Equilibrium Glide (QEG) scheme. The aerodynamic load factor and the dynamic pressure path constraints are enforced by further planning of the bank angle with the help of a constraint enforcement scheme. The maximum heating rate path constraint is enforced through the angle of attack parameterization. The Common Aero Vehicle (CAV) flight vehicle is used for the simulation purpose to test and compare the proposed method with that of the standard Particle Swarm Optimization (PSO) method and the standard Gravitational Search Algorithm (GSA). The simulation results confirm the efficiency of the proposed FPSOGSA method over the standard PSO and the GSA methods by showing its better convergence and computation efficiency.