考虑高斯能量分布的复杂表面航天器激光雷达散射特性分析

针对复杂表面航天器在激光雷达照射下散射特性模拟不准的问题,通过表面建模和激光特性修正进行了解决。该方法首先通过高斯能量分布法对激光光束模型进行修正;然后基于有限元的思想,针对航天器复杂表面非光滑、非连续以及多材质等特性,利用改进Z-buffer的消隐算法解决了复杂航天器表面建模问题;最后建立了面向激光雷达的复杂表面航天器激光雷达散射截面的计算方法。仿真分析表明:航天器不同姿态下的激光雷达散射截面精度提升了14.58%,为后续面向激光雷达的隐身设计奠定了基础。     

考虑测量约束的非合作目标近距离快速导引控制方法

研究了考虑测量约束的非合作目标近距离快速导引控制方法。首先,基于C-W方程建立了解析形式的径切联合近距离快速导引控制模型,并采用微分修正方法将解析结果进行修正;然后推导了任意初始条件下,径切联合控制双脉冲与视场角的解析关系;最后基于相对偏心率矢量建立了径切联合控制的控后效果评估模型。仿真结果表明:提出的控制方法和控后效果评估模型有效。     

月球探测任务测控系统总体设计技术研究

我国的探月工程采用"绕、落、回"三步走发展战略,测控系统作为工程五大系统之一,通过探月工程建成了全球布站的深空测控网和18 m测控网,并圆满完成了历次任务对探测器的测控,在任务分析与设计、测定轨和链路设计等方面积累了大量实战经验.本文以嫦娥四号中继星和探测器两次发射任务为例,系统梳理了我国深空测控网和18 m测控网现状...     

Towards intelligent design optimization: Progress and challenge of design optimization theories and technologies for plastic forming

Plastic forming is one of enabling and fundamental technologies in advanced manufacturing chains. Design optimization is a critical way to improve the performance of the forming system, exploit the advantages of high productivity, high product quality, low production cost and short time to market and develop precise, accurate, green, and intelligent (smart) plastic forming technology. However, plastic forming is quite complicated, relating to multi-physics field coupling, multi-factor influence, multi-defect constraint, and triple nonlinear, etc., and the design optimization for plastic forming involves multi-objective, multi-parameter, multi-constraint, nonlinear, high-dimensionality, non-continuity, time-varying, and uncertainty, etc. Therefore, how to achieve accurate and efficient design optimization of products, equipment, tools/dies, and processing as well as materials characterization has always been the research frontier and focus in the field of engineering and manufacturing. In recent years, with the rapid development of computing science, data science and internet of things (IoT), the theories and technologies of design optimization have attracted more and more attention, and developed rapidly in forming process. Accordingly, this paper first introduced the framework of design optimization for plastic forming. Then, focusing on the key problems of design optimization, such as numerical model and optimization algorithm, this paper summarized the research progress on the development and application of the theories and technologies about design optimization in forming process, including deterministic and uncertain optimization. Moreover, the applicability of various modeling methods and optimization algorithms was elaborated in solving the design optimization problems of plastic forming. Finally, considering the development trends of forming technology, this paper discusses some challenges of design optimization that may need to be solved and faced in forming process.     

R/S方法求解网络流量自相似参数的实现与应用

基于网络流量具有统计自相似性的理论,通过计算自相似参数Hurst值来检验流量的自相似程度。采用R/S方法对流量数据进行分析,给出了R/S方法详细的实现算法,通过实验的分析与比较,验证了自相似性的存在。自相似性是正常网络流量具备的特征,当流量发生异常时,Hurst值会出现明显的变化,本文将这一变化应用于DDoS攻击检测做了初步的探讨。基于自相似理论的网络流量异常检测技术与传统的基于统计异常技术和数据包特征匹配等方法相比,具有更高的准确性和可靠性。     

非结构网格二维理想MHD绕流逆风格式解法

在非结构网格上发展了针对二维理想磁流体方程组的逆风格式求解方法.控制方程中的对流项采用AUSM格式处理,时间推进采用显式5步龙格-库塔方法.为了消除计算中产生的磁场散度的影响,引入了双曲型散度清除方法.通过对磁流体激波管问题的求解验证了该方法对激波的捕捉能力,对有均匀磁场干扰下的喷管流动情况进行了数值模拟,并与文献中结果进行了对比.计算结果显示了磁场对磁流体流动的干扰效应,该结果与参考文献中的数值模拟结果相吻合.     

用推力矢量控制技术改进超声速飞行器空气动力特性

为了提高某超声速飞机的空气动力学效率和机动性能,本文采用低阶的三维板块法和DATCOM半经验公式,在亚声速和超声速条件下,对不同马赫数和迎角情况计算了基本气动外形的飞机空气动力学特性、表面压力分布以及最大升力。此外还开发了一套软件以实现由引进的先进气动操纵面（如鸭翼等）控制的二维推力矢量技术。试验结果表明：气动操纵面结合推力矢量技术能够产生足够的低头力矩,且有能力满足高度机动飞行时的稳定性要求。此外,不论是亚声速还是超声速飞行,气动操纵面均可以提高气动效率5％-6％。     

Fast cooperative trajectory optimization and test verification for close-range satellite formation using Finite Fourier Series method

The process of formation reconfiguration for close-range satellite formation should take into account the risk of collisions between satellites. To this end, this paper presents a method to rapidly generate low-thrust collision-avoidance trajectories in the formation reconfiguration using Finite Fourier Series (FFS). The FFS method can rapidly generate the collision-avoidance three-dimensional trajectory. The results obtained by the FFS method are used as an initial guess in the Gauss Pseudospectral Method (GPM) solver to verify the applicability of the results. Compared with the GPM method, the FFS method needs very little computing time to obtain the results with very little difference in performance index. To verify the effectiveness, the proposed method is tested and validated by a formation control testbed. Three satellite simulators in the testbed are used to simulate two-dimensional satellite formation reconfiguration. The simulation and experimental results show that the FFS method can rapidly generate trajectories and effectively reduce the risk of collision between satellites. This fast trajectory generation method has great significance for on-line, constantly satellite formation reconfiguration.     

Simulation study of motion of charged particles trapped in Earth’s magnetosphere

This article aims to understand the motion of the charged particles trapped in the Earth’s inner magnetosphere. The emphasis is on identifying the numerical scheme, which is appropriate to characterize the trajectories of the charged particles of different energies that enter the Earth’s magnetosphere and get trap along the magnetic field lines. These particles perform three different periodic motions, namely: gyration, bounce, and azimuthal drift. However, often, the gyration of the particle is ignored, and only the guiding center of the particle is traced to reduce the computational time. It is because the simulation of all three motions (gyro, bounce, and drift) together needed a robust numerical scheme, which has less numerical dissipation. We have developed a three-dimensional test particle simulation model in which the relativistic equation of motion is solved numerically using the fourth and sixth-order Runge-Kutta methods. The stability of the simulation model is verified by checking the conservation of total kinetic energy and adiabatic invariants linked with each type of motion. We found that the sixth-order Runge-Kutta method is suitable to trace the complete trajectories of both proton and electron of a wide energy range, 5 keV to 250 MeV for L = 2 – 6. We have estimated the bounce and drift periods from the simulations, and they are found to be in good agreement with the theory. The study implies that a simulation model with sixth-order Runge-Kutta method can be applied to the time-vary, non-analytical form of magnetic configuration in future studies to understand the dynamics of charged particles trapped in Earth’s magnetosphere.     

闪电成像仪的实验室定标

闪电成像仪是对地静止的天底成像遥感器,被优化适于在白天和夜间探测和定位闪电。实验室定标是发射前的业务,其作用在于保证遥感器在轨运行的性能。文章着重讨论实验室性能定标。