一种基于多普勒频率的恒模信号直接定位方法

相比于传统的差分多普勒(DD)两步定位方法,以Amar和Weiss提出的基于多普勒频率的单步直接定位方法在低信噪比和小样本条件下具有更高的定位精度。在该类新型定位体制的基础上,提出了一种基于多普勒频率的恒模信号直接定位方法。首先,依据最大似然(ML)准则以及恒模信号的恒包络特征,建立相应的直接定位优化模型。然后,根据目标函数的代数特征将全部未知参量分成两组,并提出一种有效的多参量交替迭代算法,用以获得该优化问题的最优数值解。新算法包含了针对这两组未知参量的Newton型迭代公式,用以避免网格搜索,并能实现多维参数的"解耦合"估计。最后,推导出针对恒模信号的目标位置直接估计方差的克拉美罗界(CRB)。数值实验验证了新方法的优越性。     

Flight path estimation using frequency measurements from a wideaperture acoustic array

A narrowband technique based on the acoustical Doppler effect is proposed for estimating the trajectory of a turbo-prop aircraft in level flight with constant velocity as it transits over a ground-based passive acoustic sensor array. The basic principle is to measure the temporal variation of the instantaneous frequency (IF) of the acoustic signal received by each sensor and then to minimize the sum of the squared deviations of the IF estimates from their predicted values over a sufficiently long period of time for all sensors. The technique provides estimates of the propeller blade rate and the five source motion parameters that describe the aircraft trajectory. The six dimensional minimization problem is reduced to a five dimensional maximization problem, which is solved numerically using the quasi-Newton method. A simple method is described that provides the initial parameter estimates required for the numerical maximization. The effectiveness of the motion parameter estimation technique is verified using real acoustic data recorded from a wide aperture microphone array during various transits of a turbo-prop aircraft     

Passive localization of frequency-agile radars from angle andfrequency measurements

It is well known that the position of a stationary radar can be estimated by a single moving observer from angle and/or frequency measurements taken passively at different points in its trajectory. Depending on the measurement set different localization methods result: the bearing method (BM), the frequency method (FM), and the combined method (CM). Previous studies analyze the three methods on the basis of constant emitter frequencies. However, radars with constant emitter frequencies are not realistic. Frequency drift and frequency hopping have to be taken into account. Therefore, to include radars the emitter model has been extended by drift and frequency hopping in this study, and the estimation methods have been reanalyzed. The effects of the model extensions become transparent in a parametric Cramer-Rao (CR) analysis. The results obtained in this way are confirmed by Monte Carlo simulations taking maximum likelihood (ML) as estimation procedure     

传感器位置误差条件下的约束总体最小二乘时差定位算法

 现代定位系统中,传感器往往被安放在运动平台上,其位置无法精确得知,存在估计误差,将严重影响对目标的定位精度。针对这一问题,提出基于约束总体最小二乘(CTLS)的到达时差(TDOA)定位算法。首先通过引入中间变量,将非线性TDOA定位方程转化为伪线性方程,再利用CTLS技术,全面考虑伪线性方程所有系数中的噪声。在此基础上推导了定位方程的目标函数,再根据牛顿迭代方法,进行数值迭代,快速得到精确解。采用一阶小噪声扰动分析方法,对该算法的理论性能进行了分析,证明了算法的无偏性和逼近克拉美-罗下限(CRLB)。仿真实验表明,该算法克服了现有总体最小二乘(TLS)算法不能达到CRLB、两步加权最小二乘(two-step WLS)算法在较高噪声时性能发散的缺陷,在较高噪声时定位精度仍然能达到CRLB。     

一种新的基于TDOA与GROA的无源定位算法

针对基于到达时间差(TDOA)与到达增益比(GROA)的辐射源无源定位问题,提出了一种新的定位算法。首先通过引入一个中间变量,根据TDOA和GROA测量模型,构造一个约束加权最小二乘(CWLS)估计。由于这个CWLS问题是非凸的优化问题,现有的方法不能很好地求解。为此,提出了一种有效的方法可以求解到其全局最优解。最后,所提算法被推广到观测站存在自定位误差时的定位求解。计算机仿真结果验证了所提算法能够获得优于传统两步加权最小二乘法(2WLS)的定位性能,能够在更大的噪声条件下达到克拉美罗下界(CRLB)。     

ATS-6 Interferometer

The Applications Technology Satellite-6 (ATS-6) RF interferometer is utilized primarily as a precision 3-axis attitude sensor having an unambiguous field of view of 350°. This function requires two separated ground transmitters, each using one of the two available frequency channels or sharing a single channel by time multiplexing. For 3-axis control, one uplink transmitter can provide 2-axis attitude (pitch and roll) with other sensors (e.g., a Polaris tracker) providing yaw attitude. By utilizing two uplink transmitters and the Earth sensor or three time multiplexed uplink transmitters, the interferometer can also provide measurements of ATS-6 spacecraft orbit position. Uplink frequencies are 6.150 and 6.155 GHz. The receiving antennas are spaced at 19.95 wavelengths (?) for the vernier baseline and 1.66 ? for the coarse baseline. Spacecraft system weight is 8.39 kg (18.5 lb) and power requirement is 15.5 W. Flight evaluation results are given for the interferometer including R F link budgets, modulation of uplink carrier, signal-to-noise ratio, and dropout behavior. A hardware calibration model is described, containing major biases in the phase measurements. Techniques for flight calibration as both an attitude and spacecraft position sensor are outlined . Flight testing has shown that on-line calibration of receiver/converter biases must be performed on a short term routine basis. Interferometer resolution was found to be 0.00140 space angle with negligible noise (jitter) at transmitted power levels above 72 dBW. As an attitude sensor, the interferometer has demonstrated the ability to provide stabilization to better than 0.     

Aircraft flight parameter estimation using acoustic multipath delays

The signal emitted by an airborne acoustic source arrives at a stationary sensor located above a flat ground via a direct path and a ground-reflected path. The difference in the times of arrival of the direct path and ground-reflected path signal components, referred to as the multipath delay, provides an instantaneous estimate of the elevation angle of the source. A model is developed to predict the variation with time of the multipath delay for a jet aircraft or other broadband acoustic source in level flight with constant velocity over a hard ground. Based on this model, two methods are formulated to estimate the speed and altitude of the aircraft Both methods require the estimation of the multipath delay as a function of time. The methods differ only in the way the multipath delay is estimated; the first method uses the autocorrelation function, and the second uses the cepstrum, of the sensor output over a short time interval. The performances of both methods are evaluated and compared using real acoustic data. The second method provides the most precise aircraft speed and altitude estimates as compared with the first and two other existing methods.     

一种针对恒模信号的运动单站直接定位算法

相比于常规的"测向+位置估计"两步定位模式,以Weiss等提出的目标直接位置确定(DPD)算法具有估计精度高、分辨能力强和无需数据关联等诸多优点。基于该类定位算法的基本理念,提出了一种利用单个运动天线阵列对恒模(即相位调制)信号的DPD算法。首先,依据最大似然(ML)准则以及恒模信号的恒包络特征,建立了相应的直接定位优化模型;接着,根据优化函数的代数特征提出了一种有效的多参量交替迭代算法,用以获得ML估计器的最优数值解;此外,推导了针对恒模信源的位置直接估计方差的克拉美罗界(CRB),从而为新算法的定位精度提供定量的理论下界。仿真实验表明:相比于已有的基于单个运动天线阵列的直接定位算法以及传统的两步定位算法,通过利用恒模信号的恒包络特征可以明显提高目标直接定位的估计精度。     

Passive Array Tracking of a Continuous Wave Transmitting Projectile

Differential Doppler measurements by a passive array are used to track an unstable continuous wave (CW) source moving in a ballistic trajectory, e.g., a projectile carrying a proximity fuse. The ballistic equations of motion couple frequency measurements at various sections along the track with the track parameters at any arbitrary time, e.g., at impact. A nonlinear weighted leastsquare method is used to estimate the track parameters, and the resulting error covariance matrix is derived. A numerical example demonstrates the relative contributions of various frequency measurements to the estimation accuracy.     

Periodic acoustic source tracking using propagation delayed measurements

There exist a large class of acoustic sources which have an underlying periodic phenomenon. Unlike the well-studied Bearings-Only Tracking(BOT) of an aperiodic acoustic source,this paper considers the problem of tracking a periodic acoustic source. For periodic acoustic tracking, the signal emission time is known. However, the true measurement reception time is unknown because it is corrupted by noise due to propagation delay. We augment the sensor’s signal reception time onto bearing measuremen...     

基于定位误差修正的运动目标TDOA/FDOA无源定位方法

针对时差(TDOA)、频差(FDOA)无源定位的两步加权最小二乘(TSWLS)方法定位均方根误差(RMSE)和定位偏差适应测量噪声能力差的问题,在分析了影响两步法定位性能的因素基础上提出一种基于一阶泰勒级数展开的定位误差修正方法。该方法的第1步和两步法相同;其第2步避免了两步法第2步中引入估计偏差的平方运算,利用一阶泰勒级数展开得到第1步定位误差的线性最小均方估计,修正第1步定位结果得到目标位置和速度的最终估计,从理论上证明了该方法可以达到定位的克拉美罗下限(CRLB)。计算机仿真对比了新方法和TSWLS方法、基于泰勒级数(TS)展开的迭代极大似然(ML)方法以及约束总体最小二乘(CTLS)方法的定位性能,新算法复杂度和两步法相当,且均方误差和定位偏差低于两步法、泰勒级数法和CTLS方法。     

Radar Measurement Noise Variance Estimation with Several Targets of Opportunity

A number of methods exist to track a target's uncertain motion through space using inherently inaccurate sensor measurements. A powerful method of adaptive estimation is the interacting multiple model (IMM) estimator. In order to carry out state estimation from the noisy measurements of a sensor, however, the filter should have knowledge of the statistical characteristics of the noise associated with that sensor. The statistical characteristics (accuracies) of real sensors, however, are not always available, in particular for legacy sensors. A method is presented of determining the measurement noise variances of a sensor, assumed to be constant, by using multiple IMM estimators while tracking targets whose motion is not known---targets of opportunity. Combining techniques outlined in [2] and [6], the likelihood functions are obtained for a number of IMM estimators, each with different assumptions on the measurement noise variances. Then a search is carried out over a varying grid of IMMs to bracket the variances of the sensor measurement noises. The end result consists of estimates of the measurement noise variances of the sensor in question.     

基于Mu-leval法的湍流猝发频率检测技巧研究

条件采样技术是目前最成熟、使用最广的湍流猝发频率检测方法,其中的Mu-level法以其原理简单、门限无关区域宽等优点,长期被湍流研究者所使用。针对Mu-level法分析结果易受试验及检测参数影响的问题,论文详细探讨了该方法用于湍流猝发频率检测的适应性和提高其检测精度的技巧。文中所用湍流流场数据是由配备单直丝探头的IFA300恒温热线风速仪在某小型专用风洞试验段中心截面处测量获得。通过对不同法向检测位置、采样频率、采样时间、门限值L及附加判定条件下湍流猝发频率的检测和对比分析,获取了各因素对湍流猝发频率检测的影响规律,探讨了提高湍流猝发频率检测准确性的可行途径,并总结了一套基于Mu-leval法的湍流猝发频率四步测试方法（试采样、试分析、采样、检测分析）。     

The Galileo Plasma wave investigation

The purpose of the Galileo plasma wave investigation is to study plasma waves and radio emissions in the magnetosphere of Jupiter. The plasma wave instrument uses an electric dipole antenna to detect electric fields, and two search coil magnetic antennas to detect magnetic fields. The frequency range covered is 5 Hz to 5.6 MHz for electric fields and 5 Hz to 160 kHz for magnetic fields. Low time-resolution survey spectrums are provided by three on-board spectrum analyzers. In the normal mode of operation the frequency resolution is about 10%, and the time resolution for a complete set of electric and magnetic field measurements is 37.33 s. High time-resolution spectrums are provided by a wideband receiver. The wideband receiver provides waveform measurements over bandwidths of 1, 10, and 80 kHz. These measurements can be either transmitted to the ground in real time, or stored on the spacecraft tape recorder. On the ground the waveforms are Fourier transformed and displayed as frequency-time spectrogams. Compared to previous measurements at Jupiter this instrument has several new capabilities. These new capabilities include (1) both electric and magnetic field measurements to distinguish electrostatic and electromagnetic waves, (2) direction finding measurements to determine source locations, and (3) increased bandwidth for the wideband measurements.Deceased     

高级波束成形在旋转声源定位中的应用

为了使高级波束成形中的函数波束成形、压缩感知波束成形、正交波束成形在旋转声源定位中获得广泛应用,对3种高级波束成形在旋转声源定位中的应用进行了研究,从声源空间分辨率,动态范围以及声源功率积分上与传统旋转波束成形和DAMAS(deconvolution approach for the mapping of acoustic sources)反卷积作对比。仿真与实验结果表明:3种高级波束成形均可以应用到旋转声源定位中,并且均能显著提升旋转声源空间分辨率和动态范围以及拥有较高的计算效率。函数波束成形在低频段的空间分辨率低于DAMAS并且容易产生较高的声源功率积分误差。压缩感知波束成形整体性能与DAMAS相近,并且在低频段的空间分辨率比DAMAS有优势。正交波束成形在低频段容易产生声源定位位置误差,抗干扰能力较弱,并且声源功率积分整体低于DAMAS。      

基于声发射的铝蜂窝板超高速撞击损伤模式识别方法

为通过声发射技术识别铝合金蜂窝板超高速撞击(HVI)的损伤状态,提出一种基于神经网络的损伤模式识别方法。通过超高速撞击实验获取声发射信号,结合精确源定位技术、时频分析技术、小波分析技术及模态声发射技术,提出了10个与损伤相关的特征参数,通过非参数检验分析其与损伤的关系,设计了一种基于贝叶斯正则化BP神经网络的超高速撞击损伤模式识别方法。建立最优网络模型,通过不同参数组合识别能力分析,优选出2种特征参数组合,通过非同源样本对其损伤模式识别能力进行验证。结果表明:传播距离与损伤模式无关,却是识别损伤模式的重要参数;125~250kHz频域的自动加窗小波能量比会降低损伤模式的识别能力;采用贝叶斯正则化的BP神经网络可以较好地识别蜂窝板超高速撞击损伤模式,参数组合为传播距离、上升时间、持续时间、截止频率、4个自动加窗小波能量比及小波能量熵,共9个参数,对任意选取非同源样本识别错分率仅为9.38%。     

Track formation with bearing and frequency measurements in clutter

Target motion analysis from a narrowband passive sonar that yields bearing and frequency measurements in the presence of false detections (clutter) in a low-SNR (low signal-to-noise ratio) environment is discussed. The likelihood function used to compute the maximum likelihood estimation of the track parameters (localization and frequency) incorporates the false alarms via the probabilistic data association technique. The Cramer-Rao lower bound is calculated and results obtained from simulations are shown to be compatible with it. A test of track acceptance is also presented     

A fault tolerant model for multi-sensor measurement

Multi-sensor systems are very powerful in the complex environments.The cointegration theory and the vector error correction model,the statistic methods which widely applied in economic analysis,are utilized to create a fitting model for homogeneous sensors measurements.An algorithm is applied to implement the model for error correction,in which the signal of any sensor can be estimated from those of others.The model divides a signal series into two parts,the training part and the estimated part.By comparing the estimated part with the actual one,the proposed method can identify a sensor with possible faults and repair its signal.With a small amount of training data,the right parameters for the model in real time could be found by the algorithm.When applied in data analysis for aero engine testing,the model works well.Therefore,it is not only an effective method to detect any sensor failure or abnormality,but also a useful approach to correct possible errors.     

GNSS驯服芯片级原子钟方法研究CSCD

芯片级原子钟是一种体积小且功耗低的高精度时钟源,具有广泛的用途。针对这一特点,设计了基于GNSS的芯片级原子钟驾驭算法。以GNSS系统时作为参考,测量芯片级原子钟与GNSS系统时间的钟差,并对芯片级原子钟进行钟差建模,获取其特征参数。通过乒乓法计算出钟驾驭调整量,对芯片级原子钟进行控制,最终将芯片级原子钟驾驭到GNSS系统时间上。经过实验验证,在驾驭时间常数为100s的情况下,芯片级原子钟与GNSS系统时间的时钟同步误差在-7.5~7.5ns之间;1h频率准确度为5.8×10-13;平均时间为10000s时的频率稳定度为3×10-13。     

A Linear-correction Least-squares Approach for Geolocation Using FDOA Measurements Only

  A linear-correction least-squares(LCLS) estimation procedure is proposed for geolocation using frequency difference of arrival (FDOA) measurements only. We first analyze the measurements of FDOA, and further derive the Cram閞-Rao lower bound (CRLB) of geolocation using FDOA measurements. For the localization model is a nonlinear least squares(LS) estimator with a nonlinear constrained, a linearizing method is used to convert the model to a linear least squares estimator with a nonlinear constrained. The Gauss-Newton iteration method is developed to conquer the source localization problem. From the analysis of solving Lagrange multiplier, the algorithm is a generalization of linear-correction least squares estimation procedure under the condition of geolocation using FDOA measurements only. The algorithm is compared with common least squares estimation. Comparisons of their estimation accuracy and the CRLB are made, and the proposed method attains the CRLB. Simulation results are included to corroborate the theoretical development.