天地基联合多星定轨及精度分析

数据中继卫星和双星定位系统通常由2或3颗地球同步卫星和数颗近地卫星组成,这些系统所提供的“星-星”测量数据提出了多星同时定轨的需求。文章介绍了已知天基星星历定轨和未知天基星星历定轨的主要差别,建立了距离和观测量的测量模型,描述了多星同时定轨的技术难点,分析了整个系统的定轨精度。     

Structural optimization for multiple structure cases and multiple payload cases with a two-level multipoint approximation method

This paper is to address structural optimization problems where multiple structure cases or multiple payload cases can be considered simultaneously. Both types of optimization problems involve multiple finite element models at each iteration step, which draws high demands in opti-mization methods. Considering the common characteristic for these two types of problems, which is that the design domain keeps the same no matter what the structure cases or payload cases are, both problems can be formulated into the unified expressions. A two-level multipoint approxima-tion (TMA) method is firstly improved with the use of analytical sensitivity analysis for structural mass, and then this improved method is utilized to tackle these two types of problems. Based on the commercial finite element software MSC.Patran/Nastran, an optimization system for multiple structure cases and multiple payload cases is developed. Numerical examples are conducted to ver-ify its feasibility and efficiency, and the necessity for the simultaneous optimizations of multiple structure cases and multiple payload cases are illustrated as well.     

飞机结构多处损伤研究现状

多损伤是老龄飞机最主要的损伤形式,在文中介绍了多损伤应力强度因子的计算方法和多裂纹连通准则,飞机结构多损伤裂纹扩展模型和可靠性分析研究现状.     

多处损伤的疲劳裂纹扩展分析方法研究

多处损伤（ＭＳＤ）影响老龄飞机结构完整性的重要因素之一。本文以线弹性断裂力学为基础,建立了一套工程适用且具有良好预测精度的ＭＳＤ疲劳裂纹扩展分析方法。     

Trajectory optimization of multiple asteroids exploration with asteroid 2010TK7 as main target

In this study, the Earth’s Trojan asteroid 2010 TK₇ is selected as the rendezvous target. The multiple flyby sequence of asteroid exploration was proposed by optimizing the probe’s orbit. Impulsive maneuvers and low-thrust propulsion were used respectively to design the trajectories of the multiple asteroids exploration mission. Under impulsive maneuvers, gravity assist technique was adopted to reduce fuel consumption. First a reference orbit with only 2010 TK₇ as the rendezvous target was designed. Then five asteroids near the reference orbit were selected as candidates. Finally, we obtained a multiple asteroids exploration sequence of three asteroids based on gravity assist technique and genetic algorithm, and an additional velocity impulse of 0.4?km/s was required. In the subsequent section, a sixth-degree inverse polynomial shape-based method is applied to the low-thrust trajectory design of 2010 TK₇, and the exploration sequence under the action of low-thrust propulsion was provided.     

再入飞行器壳体气动噪声响应分析和试验验证

本文利用再入飞行器壳体气动噪声试验结果和MSC／NASTRAN软件完成了再入飞行器壳体复杂结构气动噪声的响应分析与试验验证，取得了令人满意的结果：0－1000Hz范围的振动加速度响应均方根值的计算值相对试验测量值的相对误差低于30％，响应分析和试验验证的研究表明，利用模态试验结果修正动力学计算模型保证其低阶模态参数准确，同时有限元网格必须满足一定的细化标准，保证包括高阶模态在内的模态数（避免高阶模记的遗漏）才能得到符合实际的计算结果。     

基于地理位置信息的无收敛多测度卫星网络路由算法研究

设计了一种基于地理位置信息的无收敛多测度的卫星网络路由算法CFR,算法根据地理位置关系、延迟和链路丢包率三种测度计算路由,满足不同应用的服务质量要求.当有数据到达时,卫星根据地理位置关系、网络拓扑和链路状态实时计算数据传输路径,避免了路由收敛过程.在此基础上,为有效均衡卫星网络负载,卫星将链路负载信息通告给数据传输路径上各颗卫星,卫星根据负载调节数据传输路径,有效地均衡了网络负载,减少了数据丢失,增加了吞吐量.     

基于角度分集的机载超宽带MIMO天线设计

为了提高机载通信设备信道容量和进一步减小天线安装空间,提出一种采用角度分集技术的超宽带（UWB）多输入多输出（MIMO）天线。该天线将Vivaldi天线和超宽带槽天线进行了集成设计,无需采用解耦结构便可获得较高的端口隔离度,大大提高了数据传输率。通过在Vivaldi天线辐射臂上开一对方形缝隙和在介质板背面增加长方形辐射贴片,可以有效减小天线的尺寸,设计的UWB-MIMO天线尺寸为36 mm×36 mm×0.8 mm。给出了天线的设计流程,加工了天线实物,并对其进行了测量。仿真和实测结果表明MIMO天线具有超宽的阻抗带宽,可以覆盖整个3.1~10.6 GHz超宽带频段。Vivaldi天线阻抗带宽为2.8~15.9 GHz,UWB槽天线阻抗带宽为1.8~12.7 GHz,天线端口隔离度均在-10 dB以下。测量了天线的辐射性能和增益特性,实测结果与仿真结果吻合较好,证明了该天线的有效性。该天线可以应用于超宽带无线通信系统和机载阵列天线系统中。     

Collision free 4D path planning for multiple UAVs based on spatial refined voting mechanism and PSO approach

In this paper, a four-dimensional coordinated path planning algorithm for multiple UAVs is proposed, in which time variable is taken into account for each UAV as well as collision free and obstacle avoidance. A Spatial Refined Voting Mechanism(SRVM) is designed for standard Particle Swarm Optimization(PSO) to overcome the defects of local optimal and slow convergence.For each generation candidate particle positions are recorded and an adaptive cube is formed with own adaptive side length to indicate occupied regions. Then space voting begins and is sorted based on voting results, whose centers with bigger voting counts are seen as sub-optimal positions. The average of all particles of corresponding dimensions are calculated as the refined solutions. A time coordination method is developed by generating specified candidate paths for every UAV, making them arrive the same destination with the same time consumption. A spatial-temporal collision avoidance technique is introduced to make collision free. Distance to destination is constructed to improve the searching accuracy and velocity of particles. In addition, the objective function is redesigned by considering the obstacle and threat avoidance, Estimated Time of Arrival(ETA), separation maintenance and UAV self-constraints. Experimental results prove the effectiveness and efficiency of the algorithm.     

多元掺杂对钡铁氧体吸波性能的影响

用柠檬酸溶胶凝胶法制备了Cu、Zr共掺钡铁氧体前驱体,研究煅烧温度对其物相的影响及Cu、Zr共掺对其吸波性能的影响。研究发现前驱体[BaFe11.2(Cu0.5Zr0.5)0.8O19]在1 200℃煅烧1 h,得到了单相的钡铁氧体。随着Cu、Zr掺量的增加,铁氧体的吸波性能提高。当Cu、Zr掺入量为0.8时,铁氧体的吸波性能最好,在10.4 GHz时,最大反射损耗达-7.81 dB。