壁面催化条件对气动热环境的影响研究

为考察再入过程中壁面催化效应对气动热环境的影响,针对高超声速热化学非平衡流动条件下不同壁面条件（全催化壁面/非催化壁面）对气动加热的影响规律展开了研究。基于热化学非平衡流动特征构造了数值算法,并通过激波-膨胀风洞中开展的高焓高超声速地面试验结果进行了验证,然后考察了不同飞行高度下和典型几何外形下不同壁面条件对气动热环境的影响并分析了其影响机制。研究结果表明在50 km的飞行高度上催化效应明显,此时全催化/非催化壁面条件下热流存在明显差异,这种差异随着高度降低而减小。     

密闭金属空腔中多孔介质相变耦合传热模型研究

针对外加瞬间高能热源,由密闭金属空腔、腔体中多孔介质、多孔介质中可相变工质组合成的耦合态目标传热特性在航空航天领域的特殊应用需求,基于金属腔体、多孔介质中不可压缩流动相变工质的能量守恒、动量守恒、质量守恒等原理,以低气压环境下应用的复杂物理结构的密闭金属腔体为研究对象,建立了由高能高效热源-金属空腔-多孔介质-多孔介质中可相变工质的相变过程的传热特性的数值计算模型,通过典型物理参数状态的仿真,获取了密闭腔体内温度、压力、相变等特征参数随时间和空间变化的数值模拟结果,关键参数的仿真结果与已有试验结果对比一致性好,同时温度、压力、相变等特征参数的变化规律与传热传质理论相吻合。结果表明该建模方案思路的正确性以及仿真结果的有效性。该传热模型可推广应用于激励热源的优化设计、密闭耦合态目标的综合性能优化。     

基于肖特基二极管的太赫兹准光探测器设计方法与成像性能研究

设计了一款太赫兹准光探测器, 该探测器主要由砷化镓肖特基二极管芯片以及高阻硅透镜组成.为了减小所设计芯片的欧姆损耗, 将天线图案生长在了半绝缘砷化镓层上.在335～350GHz频率范围内, 准光探测器的实测电压响应率为1360～1650V/W, 双边带变频损耗为10.6～12.5dB.对应估算的等效噪声功率为1.65～2pW/Hz1/2.基于所设计的准光探测器进行了成像实验, 该实验分别在直接检波和外差探测两种模式间进行, 成像结果表明所设计的太赫兹准光探测器能够满足太赫兹成像方面应用.     

蛇形机器人直线运动的研究

提出一种由6个关节组成的蛇形机器人,研究了蛇形机器人的直线运动机理,在机械系统动态仿真软件ADAMS中建立蛇形机器人的运动模型,设置直线运动的关节角度时间函数。通过在ADAMS中添加各种驱动,设定运动函数,分析了地面摩擦跟蛇体的运动关系,并进行了仿真验证。结果表明,所提出的蛇形机器人能够完成设定的直线运动。     

Experimental Investigation on the Specific Heat of Carbonized Phenolic Resin-Based Ablative Materials

As typical phenolic resin-based ablative materials, the high silica/phenolic and carbon/phenolic composites are widely used in aerospace field. The specific heat of the carbonized ablators after ablation is an important thermophysical parameter in the process of heat transfer, but it is rarely reported. In this investigation, the carbonized samples of the high silica/phenolic and carbon/phenolic were obtained through carbonization experiments, and the specific heat of the carbonized samples was determined by a 3D DSC from 150 \(^{\circ }\hbox {C}\) to 970 \(^{\circ }\hbox {C}\). Structural and compositional characterizations were performed to determine the mass fractions of the fiber and the carbonized product of phenolic which are the two constituents of the carbonized samples, while the specific heat of each constituent was also measured by 3D DSC. The masses of the carbonized samples were reduced when heated to a high temperature in the specific heat measurements, due to the thermal degradation of the carbonized product of phenolic resin in the carbonized samples. The raw experimental specific heat of the two carbonized samples and the carbonized product of phenolic resin was modified according to the quality changes of the carbonized samples presented by TGA results. Based on the mass fraction and the specific heat of each constituent, a weighted average method was adopted to obtain the calculated results of the carbonized samples. Due to the unconsolidated property of the fiber samples which impacts the reliability of the DSC measurement, there is a certain deviation between the experimental and calculated results of the carbonized samples. Considering the similarity of composition and structure, the data of quartz glass and graphite were used to substitute the specific heat of the high silica fiber and carbon fiber, respectively, resulting in better agreements with the experimental ones. Furthermore, the accurate specific heat of the high silica fiber and carbon fiber bundles was obtained by inversion, enabling the prediction of the specific heat of the carbonized ablators with different constituent mass fractions by means of the weighted average method in engineering.     

Digital twin-based smart assembly process design and application framework for complex products and its case study

With rapid advances in new generation information technologies, digital twin (DT), and cyber-physical system, smart assembly has become a core focus for intelligent manufacturing in the fourth industrial evolution. Deep integration between information and physical worlds is a key phase to develop smart assembly process design that bridge the gap between product assembly design and manufacturing. This paper presents a digital twin reference model for smart assembly process design, and proposes an application framework for DT-based smart assembly with three layers. Product assembly station components are detailed in the physical space layer; two main modules, communication connection and data processing, are introduced in the interaction layer; and we discuss working mechanisms of assembly process planning, simulation, predication, and control management in the virtual space layer in detail. A case study shows the proposed approach application for an experimental simplified satellite assembly case using the DT-based assembly application system (DT-AAS) to verify the proposed application framework and method effectiveness.     

Effect of Al2O3 content on the synthesized products by the laser ignited self-propagating high-temperature synthesis reaction of Al2O3–Ti–C system

The effect of Al₂O₃ content on ignition temperature and combustion temperature, the phase composition, the density of the products and the grain size of TiC was investigated by self-propagating high-temperature synthesis reaction of Al₂O₃–Ti–C system. The results show ignition temperature increases and combustion temperature decreases with the increasing of Al₂O₃ content; the density of the products varies with Al₂O₃ content, TiC and Al₂O₃ are the two stable phases after SHS, TiC particle size decreases with the increasing of Al₂O₃ content, furthermore, the fracture type of the sintered specimens is a nearly completely intergranular mode.     

一种导弹终端侵彻多约束最优制导方法

针对地面目标精确打击及高效毁伤的需求,提出一种满足终端位置、落角及攻角约束的最优制导方法。利用比例导引项、落角约束项及加速度约束项保证终端命中多种约束条件,并且设计制导阶次实现全程加速度指令的优化分配,保证命中目标时的加速度指令收敛为小量。通过仿真计算验证了该制导方法能够满足精度、落角及攻角等终端约束条件,同时具有更好的加速度指令特性,有利于增强导弹的精确毁伤能力。     

再入飞行器禁飞区规避近似解析制导方法

针对再入飞行器的禁飞区规避问题,提出了一种基于近似解析解的禁飞区规避制导方法.所设计的制导方法,在对飞行器转弯能力分析的基础上,结合Dubins曲线的路径规划方法,求解规避需用倾侧角的近似解析解,生成禁飞区规避指令;然后为修正规避引起的航程及高度误差,通过基于能量的运动模型,进行航程及高度的解析预测-校正制导;最终实现...     

基于高斯伪谱法和有限差分结合的飞行器燃料最优轨道转移优化

为解决最优轨道短时快速转移优化问题,将高斯伪谱法和有限差分法相结合,求解最优控制的直接法和间接法,提出基于Lambert边值求解的初值范围,加快高斯伪谱法的收敛速度.并利用伪谱法得到的协态变量初值带入有限差分求解两点边值问题的精确解.仿真结果表明,对于短时间轨道转移,同伪谱法相比,改进方法的控制过程稳定无误差,精度更高...