多引力场小推力引力借力轨道设计与优化

采用序贯法设计优化小推力引力借力轨道(low-thrust gravity-assist,LTGA)时,设计步骤复杂且优化结果最优性条件难以保证.本文提出一种多引力场LTGA问题联立求解框架.首先对多引力场环境和探测器动力学模型进行统一描述和处理.设计初始化策略,利用Radau伪谱法将发射窗口、借力顺序、初始轨道搜索以及轨道优化联立求解,简化设计步骤.利用hp自适应网格精细化策略保证优化结果最优性条件.该联立框架用于求解地木转移任务,得到地球–火星–地球–木星的转移方案.本文提出的联立求解框架,简化了设计步骤,保证了优化结果的最优性条件,得到比序贯求解更优的转移方案.     

基于形状法和伪谱法的小推力借力优化研究

小推力借力飞行轨道优化是一个多变量多约束的非线性优化问题,根据形状法和伪谱法,提出一种混合优化策略,分为全局优化和局部优化两个阶段进行。在全局优化阶段采用LT-PGA模型,即通过求解形状法小推力Lambert问题,搜索满足约束条件的小推力发射窗口,得到发射、借力和到达时间点。在局部优化阶段采用伪谱法得到推力控制率,用连接点设置解决借力行星处状态量的不连续问题。数值仿真结果表明,改进方法不用事先指定推力开关机序列,优化效率高,为初始设计阶段小推力借力飞行的轨道优化问题提供有益参考。     

GSSR成像雷达应用进展及其对我国深空探测的启示

美国GSSR(Goldstone Solar System Radar)成像雷达系统在国际深空探测中扮演重要的角色,已广泛应用于月球地形测绘、火星探测、小行星轨道测定和深空探测器测控等。梳理了GSSR系统研究背景和发展现状,分析了其系统组成及对近地天体主动探测的观测原理,并着重介绍了GSSR在深空探测领域的最新应用进展,最后探讨了GSSR成像雷达对我国深空探测任务和月基雷达对地观测研究的启示。     

亚轨道飞行器任务中止再入轨迹优化设计

针对亚轨道飞行器上升段由于动力故障任务中止时再入返回的问题,考虑飞行模型简化和故障后的燃料处理方案,通过遗传算法优化设计最优返回轨迹,优化时选取经向飞行航程最远作为性能指标,并采用遗传算法,解决用于再入轨迹优化所涉及的关键问题,并进行仿真。仿真结果表明,方法不但满足飞行器返回过程中加热率、过载、动压约束以及终端状态约束,能够通过飞行航程最远消耗飞行器能量从而安全着陆,而且可以较快地搜索到全局最优解,能够用于亚轨道飞行器故障再入轨迹的优化设计。     

基于编队干涉技术的空间测量成像系统

结合干涉成像原理与空间探测中的编队飞行技术,提出一种空间干涉测量成像的方案。首先,建立了基于编队干涉技术的测量成像系统结构,利用ASPRO软件,通过建模和仿真分析了主要系统参数对UV覆盖性能的影响;然后,基于编队干涉系统,针对月球探测任务设计了一种低能耗、高灵活性的干涉成像方案;最后,利用所提方案对目标天体的测量成像进行了模拟重构和仿真分析。所提方案为下一步空间干涉测量任务的设计提供了一定参考。     

基于MVC架构的深空探测任务设计与仿真平台

深空探测任务的高风险、高投入、高复杂性,需要一套专业的软件对其进行设计与评估,因此,自主研发了一套用于深空探测任务设计与仿真的软件平台.平台包括初始轨道设计、引力辅助轨道设计、精确轨道设计、丰富的轨道优化设计算法、任务管理以及实时仿真等功能.平台采用MVC三层架构模式,将视图层和逻辑层解耦,满足软件工程中低耦合、高内聚的设计原则,软件的可扩展性、灵活性得到充分的提升.最后,以地-火精确轨道任务、Cassini任务为例验证了系统的可靠性和精确性,能满足实际工程的设计要求.     

天基发射方案与规划策略仿真研究

为更好地发挥天基系统的能力,研究天基发射方案、相关应用技术以及远程导引路径规划.以空间平台发射追踪器与目标交会问题为例,基于飞行任务提出了三种冲量推进的发射方案及规划算法.重点分析了基于发射窗口的发射方案和基于非线性规划的发射方案,结合所设计的规划流程和规划算法,建立相应的数学模型并进行仿真.仿真结果表明,对于发射窗口的遍历计算方案能够为决策优化提供足够多的发射时机和姿态选择;非线性规划的数值寻优方案可以为规划策略提供多种约束下的最优选择方案.研究结果为天基发射任务和组合机动路径规划提供了有价值的参考.     

基于进化算法的人造卫星轨道优化设计与仿真

进化算法因其较强的搜索能力已被广泛应用于卫星轨道求解当中,但传统的方法是在轨道建模的基础上解微分方程得出,因轨道模型要考虑很多摄动因素,所以运算量巨大,充分运用STK软件强大、精确的卫星轨道机动运算功能,利用STK软件的连接模块将进化算法得到的数据输入到STK的轨道机动模块,算出卫星发射轨道并求出最佳机动方案,使算法简单可靠.最后,通过STK的轨道机动模块、三维显示模块对设计出来的轨道仿真演示.实例结果证明了该方法的有效性.     

卫星编队相对动力学方程数值解法

随着卫星技术的迅速发展,编队飞行技术得到了广泛的应用,而相对动力学数学精确模型是卫星编队飞行首先要解决的问题.为了保证卫星飞行保持稳定轨道,按Hill方程的圆轨道编队设计方法应用于椭圆轨道编队设计中,分析了相对动力学方程的精确模型.在满足椭圆轨道编队周期性运动的一般性初始化条件基础上,采用椭圆轨道编队相对动力学方程中周期解的要求,提出了一种新的数值解法.通过仿真,利用STK仿真工具,得到主从卫星的相对位置变化曲线,并对误差进行了分析,进而验证了方法的有效性和可行性.     

面向深空探测任务的实数遗传编码多星任务规划算法

针对面向深空探测任务的多星任务规划问题,综合考虑卫星对目标时间窗口、卫星姿态机动以及工作能耗等约束条件,建立了面向深空探测任务的多星任务规划问题模型,针对常规01编码在进行大规模卫星任务规划时,存在的编码长度过长等问题,提出了一种基于实数编码方式的遗传算法,以求解面向深空探测的多星任务规划问题.该算法采用了一种以目标为染色体的实数编码方式,相比传统的以时间窗口为染色体的01编码方式,缩短了染色体长度,可有效提高算法的求解效率.通过仿真算例分析,验证了基于实数编码的遗传算法对求解多星任务规划问题的正确性、合理性和有效性,并将其与基于传统01编码方式的遗传算法进行对比分析,其结果表明基于实数编码方式的遗传算法在寻优能力和计算速度上具有明显优势,这为求解面向深空探测任务的多星任务规划问题提供了一种新的思路和方法.     

Scheduling satellite launch missions: an MILP approach

The paper deals with an MILP model to schedule satellite launches with alternative launchers and different mission profiles, subject to resource constraints. The model is part of a simulation tool developed within a joint research project with the European space agency. The focus is on geostationary transfer orbit (GTO) launches of payloads, which are associated with a given time window for launch, a payload mass, and a potential revenue. A launch requires the payload, a launcher compatible with both payload mass and mission profile, a launch complex for that launcher, and a launch range (i.e., resources that are shared by the launch complexes, including a mission control station). We consider three launcher types, which differ in cost and performance, are produced at a limited rate, and cannot be stocked in large amounts. One of the launchers is also able to carry out dual launch missions, i.e., missions in which two payloads are launched together, provided that their joint mass does not exceed launcher’s mass capacity and their time windows overlap. After each launch, the launch complexes and the launch range need some latency time to be reset. Two natural objectives are minimizing the number of lost payloads and maximizing profit. Here we report experiences with a discrete-time MILP model formulation, which is rather flexible and can be extended to cope with additional problem features. Natural concerns, such as computational effort and the effect of time discretization, are addressed in the paper.     

地理信息系统设计及其实现

介绍了以VC6．0为开发工具、利用面向对象技术、以ODBC数据源为后台、运行于Windows系统的基础地理信息系统(GIS)的开发方法。该系统实现了绘制图形的矢量图形系统、管理属性数据的数据库管理系统以及实现空间查询和分析的应用与分析系统，从而实现了对象的地理位置和属性的双向查询，并介绍了空间信息统计和分析功能，以及开发多用户和C／S模式GIS系统的方法。     

VB自绘菜单流程分析

Visual Basic 6.0中使用"菜单编辑器"只能创建"平面"菜单,要得到附带图标、界面美观的菜单,需要调用API函数进行自绘菜单,而主菜单与下拉式菜单的触发事件不一样,需要响应不同的消息,使绘制的复杂性大大增加.在具体绘制过程中,首先确定消息机制,然后选取合适的API函数菜,对于菜单中经常使用的方框线条等基本图形先构造绘图函数,通过主函数调用绘图函数的方式来简化问题的复杂性,巧妙地实现了自绘菜单的期望效果.     

直线的Bresenham并行绘制算法

本文对直线的Bresenham并行绘制进行了研究,并从概率上计算了当斜率k属于（0,1/2）时,每条扫描线上的平均像素个数,发现采用并行绘制方法在该区间可节约3/4的绘制时间.根据理论分析,结合经典Bresenham画直线算法,实现了并行Bresenham画直线算法,并将绘制结果与windows绘图程序和经典的Bresenham画直线算法结果进行了比较,其绘图结果完全相同.对于扫描线多点并行绘制而言,具有很好的效果,便于硬件实现,以增强对实时绘图的响应.     

线段二维裁剪与绘制的算法性能分析

分析与讨论了几种线段二维裁减和绘制算法,为了提高图形绘制的精确度和计算速度,通过实验在Windows平台上利用C语言和DirectDraw接口实现了这些算法。针对不同的实验参数,对各个算法性能作出了比较。分析结果显示：在实现过程中可以对直线裁剪的累计误差处理,对整数除法的四舍五入处理等细节改良,从而使得绘制的图形更加精确,付出的代价非常小。实验结果表明,采用最优树裁剪算法对线段进行二维裁剪并利用步距长度片算法进行绘制,能够高效完成显示任务,结果具有较好的参考价值。     

标准JAVA中如何实现图形按钮

Java虽然已风靡全球,但用户界面在某些地方还不太令人满 意。比如说没有图形按钮,没有象Windows系统中漂亮的Teb头等,针对这一情况,介绍了如 何利用组件事件传递方法和自绘制来实现标准Java的图形按钮。 同时还介绍了特定组件在J ava中产生的相应事件。 文中所列程序已全部在Windows 98平台上JDK1.1.1.2编译中运行 通过。     

MFC应用程序拆分窗口的同步更新方法研究

本文首先介绍在MFC单文档应用程序中的基本绘图方法,以及拆分窗口如何实现同步更新的问题,然后通过一个引例逐步阐述如何提高拆分窗口更新效率的方法。     

A model, a heuristic and a decision support system to solve the scheduling problem of an earth observing satellite constellation

China plans to launch four small optical satellites and four small SAR satellites to form a natural disaster monitoring constellation. Data can be obtained by the constellation in all weather conditions for disaster alert and environmental damage analysis. The scheduling problem for the constellation consists of selecting and timetabling the observation activities to acquire the requested images of the earth surface and scheduling the download activities to transmit the image files to a set of ground stations. The scheduling problem is required to be solved every day in a typical 1-day horizon and it must respect complex satellite operational constraints as well as request preferences, such as visibility time windows, transition time between consecutive observations or downloads, memory capacity, energy capacity, polygon target requests and priorities. The objective is to maximize the rewards of the images taken and transmitted. We present a nonlinear model of the scheduling problem, develop a priority-based heuristic with conflict-avoided, limited backtracking and download-as-needed features, which produces satisfactory feasible plans in a very short time. A decision support system based on the model and the heuristic is also provided. The system performance shows a significant improvement with respect to faster and better scheduling of an earth observing satellite constellation.     

Analysis of disturbances in a leg of pitch-up maneuvering

A complex model of disturbances for a leg of pitch-up maneuvering by a carrier aircraft in launching a launch vehicle was constructed. The model incorporates the atmospheric disturbances (wind gust, jet wind, and density variations), errors in the motion parameters at the point of beginning the maneuver, and the deviation of the initial mass of a launcher aircraft from the design mass. Such a model is required for a priori estimation of the operational requirements (in normal load factor and attack angle), as well as for determination of possible initial errors in the motion of the launch vehicle due to the air launch. We present majority estimates of errors for the most unfavorable combination of disturbances and the results of statistical analysis for the disturbed-motion trajectories by the Monte Carlo method.     

Application of Genetic Algorithms for biped robot gait synthesis optimization during walking and going up-stairs

Selecting an appropriate gait can reduce consumed energy by a biped robot. In this paper, a Genetic Algorithm gait synthesis method is proposed, which generates the angle trajectories based on the minimum consumed energy and minimum torque change. The gait synthesis is considered for two cases: walking and going up-stairs. The proposed method can be applied for a wide range of step lengths and step times during walking; or step lengths, stair heights and step times for going up-stairs. The angle trajectories are generated without neglecting the stability of the biped robot. The angle trajectories can be generated for other tasks to be performed by the biped robot, like going down-stairs, overcoming obstacles, etc. In order to verify the effectiveness of the proposed method, the results for minimum consumed energy and minimum torque change are compared. A Radial Basis Function Neural Network is considered for the real-time application. Simulations are realized based upon the parameters of the 'Bonten-Maru I'humanoid robot, which is under development in our laboratory. The evaluation by simulations shows that the proposed method has a good performance.