Impact of one satellite outage on ARAIM depleted constellation configurations

Advanced Receiver Autonomous Integrity Monitoring(ARAIM) is a new technology that will provide worldwide coverage of vertical guidance in aviation navigation. The ARAIM performance and improvement under depleted constellations is a practical problem that needs to be faced and researched further. It is a shortcut that improves the availability in position domain whose key idea is to replace the conventional least squares process with a non-least-squares estimator to lower the integrity risk in exchange for a slight increase in nominal position error. The contributions given in this paper include two parts: First, the impacts of one satellite outage on different constellations are analyzed and compared. The conclusion is that GPS is more sensitive and vulnerable to one satellite outage. Second, a constellation weighted ARAIM(CW-ARAIM)position estimator is proposed. The position solution is replaced by a constellation weighted average solution to eliminate the constellation difference. The new solution will move close to the constellation solutions with respect to the accuracy requirement. The simulation results under baseline GPS and Galileo dual-constellation show that the one GPS satellite outage will knock the availability from 91% to only 50%. The performance remains stable with one Galileo satellite outage. With the assistance of the CW-ARAIM method, the availability can increase from 50% to more than80% under depleted GPS configurations. Even without any satellite outage, the proposed method can effectively improve the availability from 91.29% to 98.75%. The test results under optimistic constellations further verify that a balanced constellation is more important than more satellites on orbit and the superiority of CW-ARAIM method is still effective.     

小卫星结构的发展与展望

从结构构型、结构材料、结构连接方式和结构评价指标四个方面论述了小卫星结构的发展现状,分析了小卫星球形或准球形壳体结构、箱板式卫星平台结构、框架式立方星结构、基于特殊需求的专用化结构及多功能一体化结构的特点及其适用范围,指出了未来小卫星结构通用化、小型化、专用化、多功能一体化的多元发展趋势,提出了小卫星结构材料、连接方式和评价指标方面的发展建议,旨在为小卫星结构的创新发展提供参考。     

基于ZAM-GTFR和Hough Transform的LFM信号检测

对于诸如电子对抗、电子情报等领域，噪声环境下的未知参量信号检测是一个关键问题。本文提出了ZAM-GTFR结合霍夫变换对线性调频信号的一种新的检测方法。对于特定的复高斯白噪声环境下的线性调频信号，检测的过程等效于对ZAM-GTFR沿瞬时频率直线作积分，再用积分值与门限做比较。仿真结果证实了此检测方法的有效性。     

编队队形的等交点周期设计方法

在分析编队构形一般设计方法设计效果的基础上，提出一种等交点周期法，对一般方法进行了改进。该法编队中卫星以一个相等的角速率运行在轨道上，能实现长期的编队飞行，并给出了编队设计算例及J2摄动下的队形演变，仿真表明，用等交点周期法设计的构形，能部分地消除J2摄动的影响。     

一种热释电红外传感器控制芯片的设计

阐述了一种采用0.6μm CMOS工艺的热释电红外传感器控制芯片的设计。该芯片在[4.0 V,6.0V]电源范围内稳定工作,具有较高的电源电压抑制比和较低的温漂,并且作了抗噪声和抗交流电源干扰处理。这种控制芯片用于接收、放大、处理、控制热释电红外传感器信号,应用前景广阔。     

发动机镀镉螺栓连接件的失效分析

对一种固体发动机安全机构上的螺栓连接失效件断口进行了扫描电子显微镜、金相组织、化学成分和Ｘ射线微区元素分析。基本朝该螺栓件失效断裂原因，由于钢制螺镀之后，低熔点金属镉从螺纹根部缺陷处渗入到基体内部引起晶界脆化，在应力的作用睛导致螺栓件失效断裂。     

自抗扰技术在船载天线伺服系统中的应用研究

为减小船摇扰动对船载天线伺服系统指向及跟踪精度的影响，引入线性自抗扰控制器（LADRC）对伺服系统位置环进行改进。首先对天线伺服系统模型进行简要分析，建立系统状态空间方程；然后利用LADRC对系统进行改进，并对其参数设计进行了详细介绍，同时为提高系统动态跟踪性能，利用TD微分器提取目标速度信息进行前馈补偿；最后经实验测试验证，LADRC相对于传统PID控制器能够保持天线伺服系统动态性能不下降，同时有效提高系统的抗船摇性能。     

差分方程yn+1=A+yn/(kΣi=1αiyn-i)的全局吸引性

研究差分方程yn+1=A+yn/(kΣi=1αiyn-i),N=0,1,...正解的稳定性,其中,A∈(0,∞),αi∈(0,∞),kΣi=1αi=k,k≥1且是整数,初始条件y-k,...,y0为任意正数.阐述并证明该方程的惟一正平衡点是全局吸引子且吸引域取决于方程的系数.     

Solar-photon sail hovering orbits about single and binary asteroids

Solar-photon sails can be useful for missions towards and about asteroids. Indeed, for the interplanetary transfer phase, missions to asteroids often require a large variation in inclination and solar-photon sails perform very well for such high energy missions. In the same way, solar-photon sails are also expected to perform well in the phase about the asteroid. This paper studies single and binary asteroids’ hovering regions by using a sailcraft. In order to consider a sailcraft with its own mass and shape, the mutual polyhedral method (usually used to study asteroid dynamics) is used; therefore, the sailcraft is designed by means of tetrahedra. The procedure to obtain the hovering regions about a single asteroid is presented and an accurate analysis of the control variables is carried out. Moreover, control torques required to maintain hovering orbits are obtained by considering the gravitational torques acting on the sailcraft due to the asteroid. In the end, the theory for hovering orbits is extended to binary-asteroid systems and applied to the binary system 1999 KW4.