一种基于锚系垂直阵列的水下移动目标警戒方法

提出了一种基于锚系垂直阵列的对水下移动目标警戒的方法，论述了基于锚系垂直阵列时频瞬态特性探测和空间相关性探测的原理。利用海洋环境与目标噪声在时-频域与空间上的差异，对水下移动目标探测警戒，探测概率高且计算相对简便。垂直阵列悬挂于锚系潜标的系留缆或直接作为潜标的系留缆，布放机动灵活、适应水深范围广，可用于对水下移动目标的长周期、定点、大范围实时监测。     

基于四阶累积量的被动测向声纳高分辨力算法研究

利用高阶累积量的阵列扩展和抑制高斯噪声特性,提出1种基于四阶累积量的逆波束形成算法,并通过滑动平均进一步改善了算法。仿真结果和实验数据表明:逆波束形成算法较常规波束形成方法在空间方位分辨力和噪声抑制能力上明显提高,可以更有效地应用于被动测向声纳中。     

水下主动电场面形阵列布置及成像方法研究

随着人们对海洋资源的不断开发,水下探测技术的所需要求越来越高,为了综合解决水下黑暗复杂环境快速探测成像需求及装置安装便捷性问题,对一种水下主动电场探测阵列布置及其成像方法进行了研究。主要依据水下主动电场定位探测原理,仿照弱电鱼探测活动进行阵列布置,通过搭载发射电极与接收电极阵列模仿弱电鱼电场发射器官与电场接收器官实现目标探测。使用 FFT 处理信号得到各接收电极的幅值, 通过差分得到水下阵列接收信号的强度变化,再运用插值算法画出阵列强度图从而对目标物体进行二维成像。 实验对不同形状的金属物体进行探测并成像,验证了方法的可行性与有效性。     

基于分数阶傅里叶变换的水下目标速度估计

在高斯白噪声背景下,匹配滤波器作为线性调频信号的最优检测器,在水声信号处理中被广泛应用。 当发射信号为线性调频信号时,由水下目标径向速度引起的多普勒频移会造成回波和样本之间失配, 使匹配滤波器的检测性能下降,增加了目标速度估计的难度。 利用分数阶傅里叶变换对于线性调频信号的聚焦特性,提出了应用分数阶傅里叶变换的水下运动目标线性调频回波检测算法,完成对目标速度的估计, 推导目标运动速度与分数阶傅里叶变换阶数之间的关系,并对测量结果进行误差分析。 仿真测试表明,该算法可有效地估计混响背景下的目标径向速度,且具有良好的估计性能。     

UUV定深控制模型参数优化设计方法

合适的控制模型参数能够保证被控对象在较快的响应时间和较小的超调量下达到控制目标,无人水下航行器定深控制模型参数的优化设计对提升水下航行器使用性能具有重要意义。首先,建立了水下航行器空间运动学方程,基于 Modelica 建模语言构建了航行器虚拟样机及其定深控制模型。然后,以响应时间和超调量最小为优化目标,采用非支配排序差分进化算法建立了水下航行器定深控制模型参数多目标优化流程,基于 OPTIMUS 平台构建了水下航行器定深控制模型参数优化设计工作流。以某水下航行器为对象的实验结果表明：所提方法可快速获得较优的 PID 控制模型参数,优化后的水下航行器定深运动控制特性显著改善。     

基于恒虚警检测的图像声呐目标跟踪

无人化、智能化的目标探测与跟踪是未来水下探测的必然趋势。针对水下移动小目标,通过固定位置的声呐接收的角度与距离二维信息,提出了一套自动跟踪方法。首先,对图像声呐进行恒虚警处理, 同时引入时域参量,通过在门限计算中增加之前时间的权重,抑制位置恒定的静态强背景干扰。之后,基于空间上目标的连续运动,提出了小目标的自动跟踪算法。湖试数据实验处理表明：该方法能有效抑制干扰, 实现水下小目标的自动探测跟踪。     

高精度和高分辨率水下地形地貌探测技术综述

为提高我国水下地形地貌探测技术水平,促进对海洋的科学认知和高效开发利用,文章综述高精度和高分辨率水下地形地貌探测技术研发进展,并分析关键技术发展方向。研究结果表明:采用机载激光、多波束、侧扫声呐、浅地层剖面、双频识别声呐、合成孔径声呐和水下三维扫描声呐等探测技术以及无人船、水下机器人和海底观测网等探测平台,可获取高精度和高分辨率水下地形地貌信息;应在提高设备性能、减小探测误差和完善数据算法等方面加大研究力度,重点发展综合探测技术,从而全面和清晰地反映水下地形地貌。     

基于多源信息融合的浅海超低频声源目标探测关键技术及实现

以多传感器信息融合理论为指导,结合现代信息处理技术与数据驱动建模及科学计算技术,研究浅海超低频声源目标激发共存地震波的复合声场中超低频声波传播特性和数据驱动建模的水下目标深度识别等关键技术,并论证了技术实现方案及路径。结果表明:以复合矢量水听器、地震波监测仪等多传感器信息融合理论为指导研究前海超低频声源目标可以克服传统声场建模存在的问题,有助于浅海超低频声源目标探测及改善海洋水下声学监测手段。在提高声呐探测设备的测量准确度、精度方面具有重要的理论意义,对周边海域为浅海的我国海防具有实战价值。     

基于稀疏贝叶斯学习的水下电场测向方法

水下电场是一种可用于对水下目标进行探测和识别的重要物理场,通过高灵敏度、低自噪声的水下电场探测系统,可实现对水下目标电场信号的远程测向。针对水下目标测向问题,提出了一种基于稀疏贝叶斯学习的水下电场测向方法。该方法采用多个探测单元同时采集处理水下目标辐射的交变电场信号,再通过稀疏贝叶斯学习方法,实现对目标电场信号波达方向的估计,最终估计出目标与探测系统的相对方位。通过湖上试验,验证了该方法的可行性与鲁棒性。相对于常规波束形成算法,在一定测试场景下,该方法对 16 Hz 频率的正弦波电场信号的测向精度提高了 4.8°。     

基于AUV的声纳水下目标实时探测机制研究

针对传统船载声纳探测水下目标存在成像分辨率低、主观性强、耗时长、应用区域局限,以及自主式水下潜航器(autonomous underwater vehicle, AUV)受水声通信限制导致数据无法实时回传、处理及目标实时探测的问题,提出了一种基于AUV的声纳水下目标实时探测机制。首先对基于AUV搭载声纳设备实施水下目标探测的系统进行了阐述;然后提出了基于AUV的声纳水下目标实时探测实施流程和关键技术;最后通过海上试验,验证了该机制在一定程度上克服了水声通信限制,实现实时、高效、智能的水下目标探测,具有较强的实际指导意义。     

Range and Doppler information from fourth-order spectra

In an active sonar system setting, a novel method is evaluated that extracts range and Doppler information from a Doppler-spread active sonar echo. The Doppler spreading is based on H. Van Trees' (1971) Gaussian amplitude modulating model, and the new method is based on the Fourier transform of a special case of the fourth-order cumulant. Specifically, from the envelope of the Gaussian amplitude modulated echo of a transmitted coded pulse train, the second-order spectrum and the Fourier transform of a special case of the fourth-order cumulant are derived and analyzed for this ability to extract range and Doppler information. It is shown that the method can theoretically extract range and Doppler information without degradation. The reason for this result is that a special case of the fourth-order cumulant is independent of the covariance of the Gaussian amplitude modulating function. These methods are also simulated and compared with the simulated results of the range-Doppler ambiguity function. This shows that the ambiguity function and the second-order spectrum are degraded due to the Gaussian amplitude modulation. The results are further demonstrated by simulating the three range-Doppler extraction methods for the received echo in noise     

Response cumulant analysis of a linear oscillator driven by Morison force

A frequency-domain cumulant spectral analysis method is developed in this study to estimate the higher-order statistics of the linear oscillator responses driven by Morison wave force. The fourth-order cumulant function of the nonlinear drag force is formulated in terms of the autocorrelation functions of water particle velocity. Price's theorem is applied to evaluate the associated higher-order joint moments. Three-dimensional Fourier Transforms are employed to obtain the trispectra of Morison force and oscillator responses. The estimated force and response kurtosis are in good agreement with those obtained from time-domain simulations; while the proposed method is found to be much more efficient. The numerical results also show that the drag force cubicization based on the least square approximation results in an overestimation of the kurtosis values; in addition, it is necessary to include the joint moments of order higher than eighth.     

Multichannel moment detectors for transients in shallow-water noise

This paper presents an evaluation of second, third, and fourth-order moments for the passive detection of transient signals in both simulated Gaussian noise and measured noise. The measured noise was recorded by a vertical array located near the San Diego, CA, harbor and is dominated at low frequencies by ship-generated noise. The detectors assume neither noise nor signal stationarity and can use single or multiple channels of data. Simulation results indicate that the fourth-order moment detector often performs better than the energy detector in the correlated measured noise, with increasing channel contributions to the moment function, resulting in increased gain. The results in simulated Gaussian noise likewise favor the fourth-order moment detector, at least for the signals with significant fourth-order moments, but the ability of the higher order detector to discriminate against correlated noise is evident. Analysis over a 30-min segment of the measured noise with selected signals demonstrates that fourth-order detection gains can be reliably expected as the noise statistics change.     

Self-monitoring sonar transducer array with internal accelerometers

To achieve the maximum detection range for active sonars, it is desirable to maximize their acoustic power. In attempting to do so, there are two limitations which are caused by cavitation on the face of the transducer and an interaction effect between transducer elements of the array. To avoid these limitations, a method is proposed for driving the array elements in phase with a uniform velocity to yield the desired radiation. For this purpose, a sonar transducer array which has internal accelerometers for monitoring the motion of the transducer element is being developed. This paper presents an outline of this sonar array and a method of high-speed numerical calculation which was developed for the prediction of the radiation characteristics of the array using the fractional Fourier transform algorithm     

Asymptotic detection performance of discrete power and higher-order spectra estimates

Several detection statistics are compared in the frequency domain based on the asymptotic probability of detection (APD) criterion. They include second-order, fourth-order, normalized fourth-order, and kurtosis estimates. The results show that for randomly occurring signals which can be characterized as non-Gaussian, the fourth-order, normalized fourth-order, and kurtosis estimates can have higher asymptotic probability of detection levels compared with second-order estimates. But only for the normalized fourth-order and kurtosis estimates do the results seem significant. Moreover, if a second-order estimate of the noise is available to normalize a fourth-order estimate of signal and noise, the resultant normalized fourth-order estimate has higher asymptotic probability of detection levels even for Gaussian signals. This result holds only when there is a significant positive covariance between the numerator and the normalizing noise sample in the denominator. On the other hand, if an independent noise sample is used to normalize a second-order or fourth-order estimate, the overall performance based on the asymptotic probability of detection will be degraded compared with the unnormalized second-order or fourth-order estimates, respectively.     

基于圆型基阵的水下声信标搜寻仪性能测试

基于声信标信号特征的快速识别技术、远距离微弱信号的快速定位技术、空域时域组合的多目标分辨技术,研发了基于圆型基阵的水下声信标搜寻仪"天科寻海一号"。通过消声水池、海上现场等试验,对其各项指标和整体性能进行了测试。该设备探测距离达3 000 m、方向分辨力达0.5°,具备同时搜寻多个声信标的能力。通过实时交会定位方法,可对大面积海域进行快速搜索及准确定位,具有重要的工程应用价值。     

Multi-Bernoulli Filter for Tracking Multiple Targets Using Sensor Array

This paper presents a multi-Bernoulli filter for tracking the direction of arrival(DOAs) of time-varying number of targets using sensor array. Our method operates directly on the measurements of sensor array and does not require any detection. Firstly, more information is reserved and compared with the after-detection measurements using a finite set of detected points. It can significantly improve the tracking performance, especially in low signal-to-noise ratio. Secondly, it inherits the advantages of the multi-Bernoulli approximation which models each of the targets individually. This allows more accurate multi-target state estimation, especially when targets cross. The proposed filter does not need clustering step and simulation results showcase the improved performance of the proposed filter.     

基于水声环境空间中多模态深度融合模型的目标识别方法研究

随着对水下目标特性研究的深入和声学探测技术的发展,基于单模态的阵列式信息融合或基于空间信息的分布式信息融合的水下目标识别方法研究已有一定成果,但针对复杂海况导致单一物理场或单一融合层次的系统识别性能提高有限等方面影响的水下目标识别方法研究还有所不足,因此,开展基于多模态深度融合模型的水下目标识别方法研究可利用模态互补,共享信息而提升识别率。文中在国内外研究基础上,深入研究了基于到达时差法和多模态方法组合的检测方法,初步形成了基于水声环境空间中多模态深度融合模型的识别框架,开展了海洋中典型自然与人为事件的信号分析与特征提取,并在此基础上,设计新型基于海底基站的被动识别系统。该系统同步记录和由位置等组成的时间序列标记声、磁和压数据,可实现高精度、高分辨率的识别。本研究可满足未来海洋观测对高性能水下目标探测、定位和跟踪系统的迫切需要,为海洋安全监管、海洋突发事件应急响应等领域提供新的技术手段和科学参考。     

基于高阶累积量的自适应波束形成

常规波束形成器仅限于利用信号的二阶统计特性。作者采用高阶累积量估计期望信号的导向矢量 (Steering Vector) ,实现了一种基于高阶累积量的自适应波束形成器 (HCAB)。该波束形成器利用信号的更高阶统计特性 ,减少了对阵列流型的依赖 ,具有较好的容差性 ,能自动跟踪信号。数值模拟实验表明该波束形成器工作良好。