Integrated track maintenance for the PMHT via the hysteresis model

Unlike other tracking algorithms the probabilistic multi-hypothesis tracker (PMHT) assumes that the true source of each measurement is an independent realisation of a random process. Given knowledge of the prior probability of this assignment variable, data association is performed independently for each measurement. When the assignment prior is unknown, it can be estimated provided that it is either time independent, or fixed over the batch. This paper presents a new extension of the PMHT, which incorporates a randomly evolving Bayesian hyperparameter for the assignment process. This extension is referred to as the PMHT with hysteresis. The state of the hyperparameter reflects each model's contribution to the mixture, and thus can be used to quantify the significance of mixture components. The paper demonstrates how this can be used as a method for automated track maintenance in clutter. The performance benefit gained over the standard PMHT is demonstrated using simulations and real sensor data     

Mixture Reduction Algorithms for Point and Extended Object Tracking in Clutter

The Bayesian solution to the problem of tracking a target with measurement association uncertainty gives rise to mixture distributions, which are composed of an ever increasing number of components. To produce a practical tracking filter, the growth of components must be controlled by approximating the mixture distribution. Two mixture reduction schemes (a joining algorithm and a clustering algorithm) have been derived for this purpose. If significant well spaced mixture components are present, these techniques can provide a useful improvement over the probabilistic data association filter (PDAF) approach, which reduces the mixture to a single Gaussian component at each time step. For the standard problem of tracking a point target in uniform random clutter, a Monte Carlo simulation study has been employed to identify the region of the problem parameter space where significant performance improvement is obtained over the PDAF. In the second part of this paper, the formal Bayesian filter is derived for an extended target consisting of an array of measurement sources with association uncertainty. A practical multiple hypothesis filter is implemented using mixture reduction and simulation results are presented.     

Sensitivity Analysis of Finite-Lag Receivers

This paper presents the sensitivity analysis of a class of receivers called finite-lag receivers, introduced by the authors in [1] through [3]. Since these receivers are based on the use of fixed-lag smoothing techniques, algorithms for the calculation of large-scale and small-scale sensitivities of fixed-lag smoothing are derived using a state augmentation approach. Steady-state analysis of these algorithms shows that an explicit relation can be obtained between sensitivity coefficients of fixed-lag smoothing and filtering. The specific case of sensitivity to variations in the measurement (channel) noise is considered as an example. These results are applied to study the sensitivity performance of the finite-lag receivers for analog communication. It is shown, for example, that finite-lag receivers for AM signals, besides being superior in performance [1]-[3], [11], in terms of output SNR or error variance, are also much less sensitive to the additive noise power level, compared to zero-lag receivers.     

着陆小行星的视线测量自主光学相对导航算法及其可观性分析

 以软着陆小行星为工程应用背景,提出了基于视线(LOS)测量的自主光学相对导航算法,并对导航算法的可观性进行了比较深入的分析研究。首先,基于透视投影模型的共线方程,给出了导航测量方程和测量敏感矩阵;接着,通过多个视线矢量的测量,应用高斯最小二乘微分修正(GLSDC)和龙贝格-马尔塔(LM)算法对探测器的位置和姿态参数进行了估计。然后,通过对误差方差阵逆矩阵秩的分析,比较详尽地分析了不同数量视线观测条件下导航算法的可观度和可观性。最后,通过数学仿真对所提出的自主导航算法的可行性进行了验证。     

Comment on "Gyro Misalignment and Encoder Quantization Effects During Multi-Axis Evaluation of Strapdown Gyros"

A recent paper1 discusses certain aspects of strapdown attitude error sources. It is pointed out here that the long term effects of these and several additional sources have previously been determined, within the framework of a complete attitude reference [4] and navigation [5] system.     

基于步进式运动模型的单兵协同导航算法设计

基于足部微惯性测量单元(MIMU)和超宽带测距的协同导航技术是一种解决卫星信号受限环境下单兵自主导航难题的有效途径.根据零速修正辅助的惯性解算特点,建立了一种单兵协同导航模型,协同导航状态为各单兵的位置和航向,系统输入为足部MIMU提供的每步位移和航向增量.将算法与相关文献中提出的两种算法进行了对比分析,该算法的优点是...     

Enhanced space integrated GPS/INS (SIGI)

Safe, reliable, and low cost space-based navigation is being provided with embedded INS/GPS systems such as the space integrated GPS/INS (SIGI). The SIGI is being used for various space vehicle applications such as launch vehicles, orbital vehicles, and re-entry vehicles. This paper describes current space vehicle navigation capabilities. The SIGI is being enhanced to provide additions to these existing capabilities with such items as higher processing and a commercial-off-the-shelf operating system. This will allow hosting of various software applications such as advanced navigation functions, flight control, guidance and vehicle management algorithms. The SIGI can host redundancy management functions by incorporating a cross channel data link card (CCDL) using a high speed firewire bus. The SIGI can then be used as a redundancy management platform which has application to current space vehicle avionics topologies incorporating distributed processing architectures     

综合导航系统信息融合模拟仿真平台设计CSCD

为解决综导系统的信息融合问题,设计了一种新型的综导系统信息融合模拟仿真研究平台。平台包括综导信息融合模拟评估导调台、惯性类导航设备模拟器、非惯性类导航设备模拟器、综合导航模拟器、电子海图系统和数据分析服务器六大模块。导调台采取一种新的船舶运动参数发生器模拟生成多种海况条件下船舶运动参数;综合导航模拟器采取多种融合算法并行运行方式,以方便比较不同算法的性能;数据分析服务器采用高性能计算机模拟公共计算环境,可研究适应未来船舶软硬件计算资源的信息融合方法。系统测试表明,基于平台的导航信息融合流程和效果满足要求,所设计的平台系统功能正常,可直接用于舰船信息融合算法的设计、分析、测试评估等工程研发工作。     

Propagation and System Accuracy Impact of Major Sensor Errors on a Strapdown Aircraft Navigator

A strapdown system is considered as an unaided inertial navigator aboard an aircraft. Presented here are simulation results detailing the propagation of navigation errors (in nautical miles) due to strapdown sensor errors for four trajectories. They indicate the type of performance that can be expected from a strapdown system utilizing good ?off the shelf? gyros and accelerometers, and dramatically illustrate the improvements necessary in these components to obtain navigation performance comparable to that available from a good gimballed inertial system. The total navigation error for each trajectory is broken down to show the contribution from each of the various error sources. This breakdown quickly reveals which are the critical error sources for a given trajectory class, and also points up the relationship that exists between each individual error source, aircraft maneuvers, and the resulting navigation error. Several of the error mechanisms are discussed at length and a set of linearized differential equations which can be used to analyze error propagations is presented. These results should be of particular interest to the system designer who is faced with the problem of specifying the sensor error parameters necessary to meet mission performance requirements. With an analysis similar to the one presented here, but structured around his own expected mission trajectories, the designer should be able to confidently predict system accuracies and intelligently perform tradeoffs on the critical system parameters.     

发动机故障诊断的主成分算法

 给出了两种基于主成分分析的发动机故障诊断算法,即主成分估计算法和主成分降维算法。这两种算法可以有效地解决发动机故障诊断中的两个技术难点,即减少故障方程中故障因子的个数以及克服故障方程的多重共线性的不良影响．在主成分估计算法中提出了最优主成分个数的概念,解决了主成分个数选择的难题．还以JT9D发动机故障诊断问题为例说明主成分分析算法的应用。研究结果表明,利用主成分降维方法可以将JT9D发动机的26个故障因子压缩到9个,或者将5个单元体的10个故障因子缩减到５个综合变量。所给出的两种算法可以在故障方程存在严重多重共线性而又无约束条件可供利用的情况下给出满意的故障诊断结果。     

准实时性前斜视INS/SAR组合导航滤波算法研究

为消除常规利用正侧视SAR图像辅助导航信息对惯性误差进行修正时的滞后影响,结合前斜视SAR成像工作特性,本文分析提出了新的准实时性组合导航滤波方案和算法,以解决SAR/INS组合导航系统中的量测滞后影响;本文分析了前斜视SAR成像辅助导航系统工作特点,分析了SAR量测输出模型;建立了准实时性前斜视INS/SAR组合导航滤波算法模型,并通过仿真分析了组合导航系统性能。仿真结果表明：采用所提出的惯性/SAR组合方案和算法,可以有效克服成规正侧视SAR辅助匹配输出滞后的影响,有效满足组合系统性能要求。     

Reflection-Free Electronic Positioning System

Many electronic positioning systems, such as hyperbolic navigation and terminal guidance, suffer large errors from reflection and diffraction of their transmitted waves. The hyperbolic system described herein is free of these errors. Utilizing a pair of frequency-swept transmitters, it discriminates against reflections by separating the direct and reflected received signals into distinct sets of beat-frequency components. It is concluded that the system can suppress multipath reflections and provide flight information particularly useful in a high-density environment.     

海上薄雾条件下退化图像的快速Retinex增强算法

目前基于Retinex 理论的各种算法对海上薄雾条件下拍摄到的退化图像有很 好的增强效果,但是这些算法主要是采用在RGB 色空间对3 个颜色通道进行高斯卷积方 法,导致处理较大尺寸图像速度慢,现针对上述现象,提出一种改进的Retinex 快速增强 算法来处理海上薄雾条件下的退化图像,此方法改变了传统Retinex 算法利用二维高斯核 进行卷积的办法, 并且考虑到HSV 空间更适于人眼视觉特征, 先将RGB 色空间转换到 HSV 空间,再将二维高斯函数简化成一维迭代高斯函数,然后应用一维迭代高斯函数对 亮度V 分量进行卷积,并对饱和度S 做相应的拉伸。根据时间复杂度理论对改进的方法 进行了分析,并经过实验验证,此算法的处理速度有明显的提高,去雾效果较明显,图 像质量得到了改善,为视觉导航系统后续的工作提供了保证。     

Real-Time Shipboard Orbit Determination Using Kalman Filtering Techniques

The real-time tracking and orbit determination program used on board the NASA tracking ship, the USNS Vanguard, is described in this paper. The computer program uses a variety of filtering algorithms, including an extended Kalman filter, to derive real-time orbit determinations (position-velocity state vectors) from shipboard tracking and navigation data. Results from Appolo missions are given to show that orbital parameters can be estimated quickly and accurately using these methods.     

基于小波域贝叶斯估计模糊萎缩的SAR图像降斑算法

提出了基于小波域高斯混合模型贝叶斯估计模糊萎缩的SAR图像降斑算法.该算法分析了SAR图像在平稳小波变换(SWT)域中的统计模型,并用高斯混合模型对其进行描述,推导出基于贝叶斯估计的信号最小均方误差(MMSE)的模糊萎缩因子.籍此再根据小波域相邻尺度间小波系数的相关性,采用分区域模糊萎缩思想,很好地得到无斑点真实信号小波系数的估计值.仿真结果表明该算法在大大抑制斑点噪声的同时,有效地保持了边缘,其性能优于改进Lee滤波、小波软阈值和SWT萎缩降斑算法.     

Multi-computer VXIbus system set up and use

VXI has matured into a flexible bus architecture with which to develop various types of instrumentation systems. This paper details the multi-computer approach used in the VXI-based system that CACI developed for the Air Force. The system, the Engine Test/Trim Automated System II (ETTAS II) is designed to test: all Air Force jet engines. The paper discusses how to integrate multiple computers in a VXI-based system, including discussions on: setting up the computers; selecting register-based versus message-based computers; setting up and using shared-memory; defining and separating tasks for each computer. The shared memory discussion talks about different ways to structure the shared memory, including setting up a system-level “Current-Value Table” (CVT) for all instruments, as well as how other devices, including another computer can access the shared memory space. The paper shows how Commercial-Off-the-Shelf (COTS) software products NI-VXI, LabVIEW, and NI-VISA (National Instruments) can be used to satisfy all these requirements. The paper shows how the multi-computer approach can be cost-effective in many cases     

Gravity modeling in aerospace applications

The science of inertial navigation has evolved to the point that the traditional gravity model is a principal error source in advanced, precise systems. Specifically, the unmodeled vertical deflections of the earth's gravitational field are a major contributor to CEP (circular error probable) divergence in precise terrestrial inertial navigation systems (INS). Over the years, several studies have been undertaken to the development of advanced techniques for accurate, real-time compensation of gravity disturbance vectors. More complex on-board gravity models which compute vertical deflection components will reduce the CEP divergence rate, but imperfect modeling due to on-board processing limitations will still cause residual vertical deflection errors. In order to eliminate or reduce gravity-induced errors in the INS requires measurement of gravity disturbance values and in-flight compensation to the inertial navigator. It is assumed in this paper that gravity disturbance values have been measured prior to the airborne mission and various techniques for compensation are to be considered. As part of a screening process in this study, several gravity compensation techniques (both deterministic and stochastic models) were investigated. The screening process involved identification of gravity models and algorithms, and developments of selection criteria for subsequent screening of the candidates.     

双视线测量相对导航方法误差分析与编队设计

空间非合作目标的相对导航是在轨维护和近距离监视任务中的关键技术,目前的研究表明仅有视线测量条件下中距离相对导航沿距离方向的观测度较差,而基于双视线测量的相对导航方法可以有效解决该问题。为此,研究了两个追踪航天器所组成的编队,在双视线测量条件下进行自主相对导航的方法。首先,详细地介绍了双视线测量相对导航方案的构成以及具体的导航算法;其次,根据两个追踪航天器与目标航天器的几何构型,推导双视线测量方法中的误差传递规律,并分析其中的影响因素;然后,对两个追踪航天器的编队构型进行设计,并分析编队构型对该方法导航性能的影响;最后,通过数值仿真对上述相关的结论进行验证。     

GNSS干扰信号检测方法研究

研究了GNSS导航接收机在干扰源条件下的干扰检测和识别技术。除常见的卫星干扰如脉冲干扰、扫频干扰、BPSK干扰、宽带高斯白噪声干扰外,还添加了QPSK和8PSK干扰进行建模分析,并提取了常见的特征参数,如信号3dB带宽和频谱峰度等。通过研究,高阶累积量被提取作为MPSK干扰类内识别的特征参数。研究了基于决策树和BP神经网络等分类器算法的干扰盲识别,并分析比较了这些分类算法的识别准确率,为抗干扰领域的研究提供了重要参考。