金属磁记忆微观机理试验研究

金属磁记忆检测机理中指出:地磁场环境中受载荷作用的铁磁试件,其内部会发生具有磁致伸缩性质的磁畴组织定向和不可逆的重新取向。将未经磁化且弯曲不同角度的无取向硅钢片和未经磁化且施加不同载荷的20#钢压缩试件制作成金相观察试样,利用B itter粉纹法观察受力程度不同的硅钢片和20#钢试件的磁畴结构,对比同种材料不同载荷试样的磁畴结构照片,分析应力对磁畴的影响。试验表明:未受力或应力集中较小时,晶粒内磁畴以片状畴为主,同一晶粒内畴壁相互平行,随着应力集中程度的增加,磁畴结构出现迷宫畴。且应力集中程度越大,迷宫畴个数越多,同时畴壁长度和间距发生改变。     

纳米CeO2/Zn复合粉末的高能球磨法制备与表征

采用高能球磨法制备了用于热浸镀锌的纳米C eO2/Zn复合粉末,并利用X射线衍射(X-ray d iffraction,XRD)、X射线光电子能谱(X-ray photoe lectron spectroscopy,XPS)、透射电镜(T ransm iss ion e lectron m i-croscopy,TEM)、扫描电镜(Scann ing e lectron m icroscopy,SEM)以及能谱分析(X-ray energy d ispers ive spec-trum,EDS)等方法,对复合粉末的显微结构、表面成分、晶粒大小、微观形貌以及元素分布进行了研究。结果表明,随着球磨时间的延长,纳米C eO2硬团聚体逐渐解聚,Zn晶粒不断细化,形成层片状复合粉末;球磨120 m in后纳米C eO2粒子分散良好,呈理想的单个均匀弥散分布状态包覆在Zn颗粒上形成近似球形的复合粒子,其粒径分布均匀。     

一种低轨星座高精度相位保持方法

针对大型低轨星座在轨运行的高精度构型保持问题,提出了一种基于极限环的高精度相位保持方法。首先,推导了实际轨道与参考轨道的平相位角偏差与半长轴偏差的关系；然后,建立了基于极限环的相位保持周期以及半长轴改变量计算方法；最后,基于推导的半长轴偏差与相位偏差的关系,提出了一种相位保持实施方法。考虑地球非球形和大气阻力的数值仿真表明：本文提出的相位保持方法能够在卫星定轨数据精度不高、数据采样间隔较大的情况下,实现低轨星座系统的高精度相位保持。     

动能拦截器运动伪装末制导律设计

针对动能拦截器末制导问题，基于运动伪装理论设计了末制导律和相应的脉冲宽度脉冲频率(PWPF)调节器。根据拦截器和目标在视线旋转坐标系下的相对运动关系建立了动力学模型。通过运动伪装特性得出的拦截条件推导出作用在视线法向上的制导指令表达式。在动能拦截器制导推力受限情况下，利用PWPF调节器调节制导指令。考虑系统的可控条件和拦截条件，对调节器参数进行了理论设计。运动伪装末制导律保证动能拦截器在制导过程起到伪装作用，具有较高的制导精度和较小的命中过载，同时经过参数设计后的PWPF调节器可以节省燃料。最后，通过数值仿真校验了所设计末制导律的正确性和有效性。     

Research on High-Precision Measurement Systems of Modern Aircraft

High-precision measurement systems of modern aircraft are studied in this paper. A measurement system with correction in the structure of inertial navigation system is introduced for highprecision aircraft. In the correction algorithms, a linear error model of the navigation system is usually used. With the aim of increasing the accuracy of the navigation system, we propose a nonlinear correction algorithm based on the state dependent coefficient representation of the nonlinear model.     

Analysis of BDS-3 distributed autonomous navigation based on BeiDou system simulation platform

Satellite autonomous navigation is an important function of the BeiDou-3 navigation System (BDS-3). Satellite autonomous navigation means that the navigation satellite uses long-term forecast ephemeris and Inter-Satellite Link (ISL) measurements to determinate its own spatial position and time reference without the support of the ground Operation and Control System (OCS) for a long time to ensure that the navigation system can normally maintain the time and space reference. This paper aims to analyze the feasibility of distributed autonomous navigation algorithms. For the first time, a ground parallel autonomous navigation test system (GPANTS) is built. The performance of distributed autonomous navigation is then analyzed using the two-way ISL ranging of BDS-3 satellites. First, the BDS simulation platform and the GPANTS are introduced. Then, the basic principles of distributed satellite autonomous orbit determination and time synchronization based on ISL measurements are summarized. Preliminary evaluation of the performance of the BDS-3 constellation autonomous navigation service under ideal conditions through simulation data. Then the performance of autonomous navigation for 22 BeiDou-3 satellites using ISL measurements is evaluated. The results show that when satellites operate autonomously for 50 days without the support of any ground station, the User Range Error (URE) of autonomous orbit determination is better than 3 m, and the time synchronization accuracy is better than 4 ns.     

近壁区流向涡生成的数值模拟

对于在湍流边界层近壁区,作为相干结构的主要特征的流向涡的产生及发展的全过程进行了研究.采用准二维的共振三波作为湍流边界层近壁区相干结构初值,用直接数值模拟方法模拟了准二维波发展到明显的三维扰动以及其中流向涡生成的整个过程,经分析发现,在该过程中,由于非线性作用,相干结构出现了明显的三维性,并产生了马蹄涡,与实验结果相一致,而且也研究了压力梯度对于流向涡生成以及发展的影响, 在逆压梯度下,流向涡的生成得更早、更快,相干结构幅值增长较快,结构变得更加复杂.这些都说明了逆压梯度对相干结构具有激励作用.     

Hardware-In-the-Loop Simulations of spacecraft attitude synchronization using the State-Dependent Riccati Equation technique

A nonlinear control technique pertaining to attitude synchronization problems is presented for formation flying spacecraft by utilizing the State-Dependent Riccati Equation (SDRE) technique. An attitude controller consisting of relative control and absolute control is designed using a reaction wheel assembly for regulator and tracking problems. To achieve effective relative control, the selective state-dependent connectivity is also adopted. The global asymptotic stability of the controller is confirmed using the Lyapunov theorem and is verified by Monte-Carlo simulations. An air-bearing-based Hardware-In-the-Loop Simulator (HILS) is also developed to validate the proposed control laws in real-time environments. The SDRE controller is discretized for implementation of a real-time processor in the HILS. The pointing errors are about 0.2° in the numerical simulations and about 1° in the HILS simulations, and experimental simulations confirm the effectiveness of the control algorithm for attitude synchronization in a spacecraft formation flying mission. Consequently, experiments using the HILS in a real-time environment can appropriately perform spacecraft attitude synchronization algorithms for formation flying spacecraft.     

太阳能飞机方案设计阶段建模与仿真

建立了太阳能飞机方案设计阶段的仿真模型,包括能量流动、太阳能采集、蓄电池、飞机运动及能量管理等部分.通过仿真比较了太阳能电池固定安装和可转动安装两种飞机方案的太阳能采集效率和续航性能.仿真结果表明,方案2的设计采集效率优势明显,在光照匮乏时飞机飞行时间较长.该模型可用于太阳能飞机方案设计阶段的验证分析,为方案的选择和改...