Research on navigation of satellite constellation based on an asynchronous observation model using X-ray pulsar

Pulsar navigation is a promising navigation method for high-altitude orbit space tasks or deep space exploration. At present, an important reason for restricting the development of pulsar navigation is that navigation accuracy is not high due to the slow update of the measurements. In order to improve the accuracy of pulsar navigation, an asynchronous observation model which can improve the update rate of the measurements is proposed on the basis of satellite constellation which has a broad space for development because of its visibility and reliability. The simulation results show that the asynchronous observation model improves the positioning accuracy by 31.48% and velocity accuracy by 24.75% than that of the synchronous observation model. With the new Doppler effects compensation method in the asynchronous observation model proposed in this paper, the positioning accuracy is improved by 32.27%, and the velocity accuracy is improved by 34.07% than that of the traditional method. The simulation results show that without considering the clock error will result in a filtering divergence.     

利用微波探测仪(ATMS)对在轨微波辐射计观测精度的模拟分析

微波辐射计的观测精度及其对数值模式同化应用的影响评估是微波辐射计观测指标设计的重要参考。基于微波探测仪(ATMS)资料,利用三维变分同化系统模拟分析在轨微波辐射计的观测精度指标。针对ATMS观测误差特征,在其观测基础上增加均值为零、标准偏差分别为0.5,1.0,1.5,2.0K的正态随机扰动,进而获得不同精度的观测模拟值序列,然后利用Harris和Kelley的辐射资料偏差订正经验方法订正不同精度的观测资料。偏差订正后,利用三维变分同化模式(WRFDA)直接同化ATMS资料。通过2016年6月6h预报场的同化试验,评估了不同观测精度的模拟资料对数值模式的同化影响。     

Orbital stability close to asteroid 624 Hektor using the polyhedral model

We investigate the orbital stability close to the unique L4-point Jupiter binary Trojan asteroid 624 Hektor. The gravitational potential of 624 Hektor is calculated using the polyhedron model with observational data of 2038 faces and 1021 vertexes. Previous studies have presented three different density values for 624 Hektor. The equilibrium points in the gravitational potential of 624 Hektor with different density values have been studied in detail. There are five equilibrium points in the gravitational potential of 624 Hektor no matter the density value. The positions, Jacobian, eigenvalues, topological cases, stability, as well as the Hessian matrix of the equilibrium points are investigated. For the three different density values the number, topological cases, and the stability of the equilibrium points with different density values are the same. However, the positions of the equilibrium points vary with the density value of the asteroid 624 Hektor. The outer equilibrium points move away from the asteroid’s mass center when the density increases, and the inner equilibrium point moves close to the asteroid’s mass center when the density increases. There exist unstable periodic orbits near the surface of 624 Hektor. We calculated an orbit near the primary’s equatorial plane of this binary Trojan asteroid; the results indicate that the orbit remains stable after 28.8375?d.     

一种针对局部结构的有限元模型修正方法

针对实际结构有限元模型（FEM）的建模误差通常仅存在于局部区域，提出了一种对局部结构单独进行模型修正的方法。首先，根据频响函数（FRF）解耦理论得到由残余结构频响函数与包含待修正参数的局部结构动刚度所重构的整体结构频响函数的拟合值，然后通过迭代优化使其与测量值的残差最小化，从而得到参数的极大似然估计。在此基础上，将残差关于参数的灵敏度以局部结构动力学矩阵表示，建立了模型修正的基本方程，利用整体结构的测试数据即可直接对分离出来的局部结构进行模型修正。最后，对喷气式飞机和三角机翼飞机分别进行了数值模拟和实验研究，验证了所提方法的可行性和有效性。结果表明，所提方法可以成功地用于仅局部区域含有建模误差的实际结构有限元模型的修正，修正后的有限元模型的动态特性与实际结构有较好的一致性。     

多种工质下螺旋波等离子体源波场结构数值模拟

针对螺旋波等离子体放电机理，开展了多种工质条件下的螺旋波放电等离子体内波场结构数值模拟研究。计算发现:氦气等离子体的Er分量在径向边界处的峰值更为突出，有利于等离子体在径向的输运，波电场径向分量决定了电流密度径向分量在内部的表现。在0.266 Pa和1.064 Pa两种气体压强条件下，通过波场结构验证了气压对于波阻尼影响的结论。波场结构是螺旋波在等离子体内传播以及能量沉积的微观体现，研究螺旋波波场结构是揭示其高电离效率的重要途径。初步探索了功率耦合机制，为实验系统优化及实验方案设定奠定理论基础。     

基于变马赫数的五孔探针三维插值方法

探讨了五孔探针气动数据的插值方法,为提高插值精度,开发了基于传统线性插值法的三维线性插值法。该方法把同一探针在不同马赫数下的校准图形成三维数据库,将实验数据通过三维图进行插值。并使用改进前后的两种插值方法分别对校准风洞测得的数据进行整理,对比结果证明:在实验工况连续变化的情况下,三维线性插值法在插值精度上要优于传统线性插值法。特别是在来流马赫数变化较大时,该方法可以改善单一校准文件处理造成的数据精度问题,可用于自动化流场采集系统,为流场高速高精度采集奠定基础。     

FDI飞机舵面损伤故障全局检测的非线性数学模型

阐述了飞机在单舵面损伤故障下 ,建立故障状态下的数学模型 ,以及同样输入条件下飞机正常运动时的数学模型 ,得到飞机在相同飞行条件下损伤时的气动系数和无损伤正常时的气动系数 ,最终得到气动系数的残差。这将为以后飞机过载残差和角加速度残差奠定基础。论文中结合一定的算例给予证实推论的正确性。     

Wave-Particle-Electric Field Synergetic Auroral Electron Acceleration

Space Science Reviews - We discuss afresh the problem of the auroral electron acceleration based on the controversy reports of Bryant, D. A. et al.: 1992, Phys. Rev. Lett. 68, 37, and Borovsky, J.:...     

对地定向三轴稳定卫星的圆锥扫描地球敏感器的数学模型

本文介绍了对地定向三轴稳定卫星的圆锥扫描式地球敏感器的姿态测量原理、输出几何关系和数学模型，并以实际例子说明大角度姿态控制时必须注意敏感器输出的轴间耦合问题     

虚拟环境系统中复杂模型的建立--3D资源在快速开发虚拟环境系统中的应用

对利用3D资源在快速开发虚拟环境系统中的方法进行了研究。在开发虚拟环境系统的过程中，复杂模型的建立是必不可少的，仅仅利用OpenGL函数编程来实现仿真是很困难的，针对该问题提出了利用3D资源进行3D文件读取和转换的两种方案，分析了虚拟环境中复杂模型的建立以及处理的基本方法，并对数控车床的仿真进行了详细介绍。