基于形状规划理论的小行星探测方法

小推力轨迹优化过程的控制率设计是典型的非线性动力学最优控制问题。针对具体的问题背景,直接优化算法和间接优化算法已被广泛应用。为了简化问题的优化模型,采用形状规划理论来模拟小推力的作用轨迹,将动力学最优控制问题转化成多项式的参数优化。结合小行星群的探测,利用粒子群优化与微分进化混合优化算法进行全局优化,为满足精度要求,再采用模式搜索局部优化算法进行二次优化。     

Analysis of noncommensurate sampling effects on the performance of PN code tracking loops

Noncoherent early-late processing (NELP) code tracking loops are often implemented using digital hardware for digital global positioning system (GPS) receivers. Noncommensurate sampling technology is widely used because it is viewed as an effective solution to cope with the drawback of digital effects. However, the relationship between the sampling rate and auto-correlation function (ACF) is not adequately characterized by traditional analysis. The principles for selecting the sampling rate are still not apparent. In order to solve this problem, we first analyzed the effects of different sampling rates on ACF and obtained the analytical form of a discrete auto-correlation function (DACF) for a noncommensurate sampling rate. Based on the result, the relationship between the step variation in DACF and NELP parameters such as sampling rate, integration time, and correlator spacing was determined. The maximum step variation size of DACF was also determined. However, considering the actual situation, additional factors such as code Doppler shift, precorrelation filter, and thermal noise may degrade the step variation of DACF. The relationship between the step variation and these factors was analyzed separately. An appropriate sampling rate and appropriate correlator spacing were proposed to achieve the typical accuracy of measurement. The numerical simulation verified the validity of the above theoretical analyses, and finally, the conclusions and design constraints for the digital GPS receiver are summarized.     

A novel method for estimating the track-soil parameters based on Kalman and improved strong tracking filters

A tracked vehicle has been widely used in exploring unknown environments and military fields. In current methods for suiting soil conditions, soil parameters need to be given and the traction performance cannot always be satisfied on soft soil. To solve the problem, it is essential to estimate track-soil parameters in real-time. Therefore, a detailed mathematical model is proposed for the first time. Furthermore, a novel algorithm which is composed of Kalman filter (KF) and improved strong tracking filter (STF) is developed for online track-soil estimation and named as KF–ISTF. By this method, the KF is used to estimate slip parameters, and the ISTF is used to estimate motion states. Then the key soil parameters can be estimated by using a suitable soil model. The experimental results show that equipped with the estimation algorithm, the proposed model can be used to estimate the track-soil parameters, and make the traction performance satisfied with soil conditions.     

粒子群算法的航天器初始轨道优化模型

为提高航天器发射段的初始轨道确定精度,及时精确地进行早期轨道段的测控,满足航天器用户的需求,提出一种基于粒子群优化算法的航天器初始轨道确定方法,将各种冗余备份设备的测量数据及测量精度等作为航天器初始轨道确定的输入元素,建立优化算法模型,以粒子群算法确定最优轨道.实验结果表明:大量实时冗余备份的不同测量精度、不同测量体制...     

电磁频谱监测数据运用研究

电磁频谱监测数据运用是频谱监测获取的数据信息服务于频管业务不可或缺的关键环节。文章提出了电磁频谱监测数据的典型存储形式,归纳梳理了不同存储形式对应的显示方式和不同显示方式的优劣特点及应用场合,并指出了频谱监测数据运用要注意的若干问题。     

基于自适应核窗宽的红外目标跟踪算法

针对传统均值漂移算法无法对对比度低、尺度变化的红外目标进行有效跟踪的问题,提出一种改进MeanShift算法.首先融合灰度和纹理两方面的信息,并分别定义背景灰度和纹理加权系数,实现了目标的准确定位;然后,提出一种基于背景和前景目标相似度的核窗宽选取算法,自动选取窗口缩放比例,得到与目标尺度一致的跟踪窗口.实验结果表明,所提出的算法能够实现对红外目标的跟踪,并且对尺度变化的目标具有较好的适应性.     

基于伽利略系统的二进制偏移载波调制技术

论文针对伽利略卫星导航信号相对于传统卫星导航信号的不同,论述了该系统中采用的BOC调制技术和BOC调制信号的一些基本特性,提出应采用余弦副载波类型的BOC信号,并在此基础上对BOC信号的多径误差进行仿真验证。仿真结果表明,余弦副载波类型的BOC（1,1）和BOC（1.5,1）的抗多径能力要优于相同参数的正弦副载波类型BOC信号。     

多测速系统最优弹道估计方法及应用

应用最优弹道估计方法,研究了多测速系统数据的融合处理技术,获得了最优弹道结果,并与高精度GPS数据进行了比对计算,发现两弹道分速度比对差值极小,计算精度达到厘米级。结果表明,最优弹道估计方法能够更好地获取高精度的弹道结果,是一种多测速系统数据处理的有效方法,在试验任务中得到了成功应用,提供了可靠的数据处理结果。     

“金属风暴”武器的耦合膛压测试弹设计

为了获得“金属风暴”武器发射过程中的耦合内弹道参数,以达到武器系统优化改进目的,设计测试“金属风暴”武器相邻弹丸之间耦合膛压的测试弹。针对30 mm小口径武器弹上空间有限、耦合膛压导致弹丸同时受弹底压力、弹前压力,力学特性复杂的问题,设计了测试弹的机械结构,将薄膜压电传感器、加速度传感器、信号采集调理、信息处理和存储、通信传输、电池等电路系统集成一体,制成了耦合膛压测试弹; 为了提高耦合膛压的测量准确性,利用加速度测试结果对薄膜传感器压力测量结果中的惯性力进行了修正。利用“金属风暴”武器开展了射击试验,检验了耦合膛压测试弹的性能。试验结果表明:耦合膛压测试弹的机械强度满足发射及回收要求,测试弹机械结构可以保护薄膜传感器不被火药气体烧蚀,经过加速度传感器修正处理可以得到弹丸发射期间的弹底压力与弹前压力,耦合膛压测试弹能够获得“金属风暴”武器的耦合内弹道参数。     

基于API调用管理的SDN应用层DDoS攻击防御机制

软件定义网络(SDN,software defined network)针对北向接口安全研究少,加之缺乏严格的访问控制、身份认证及异常调用检测等机制,导致攻击者有机会开发恶意的应用程序,造成北向应用程序接口(API,application programming interface)的滥用,不利于SDN的全面推广.针对...