Simulation of an Inertial Acoustic Navigation System With Range Aiding for an Autonomous Underwater Vehicle

This paper presents an integrated navigation system for underwater vehicles to improve the performance of a conventional inertial acoustic navigation system by introducing range measurement. The integrated navigation system is based on a strapdown inertial navigation system (SDINS) accompanying range sensor, Doppler velocity log (DVL), magnetic compass, and depth sensor. Two measurement models of the range sensor are derived and augmented to the inertial acoustic navigation system, respectively. A multirate extended Kalman filter (EKF) is adopted to propagate the error covariance with the inertial sensors, where the filter updates the measurement errors and the error covariance and corrects the system states when the external measurements are available. This paper demonstrates the improvement on the robustness and convergence of the integrated navigation system with range aiding (RA). This paper used experimental data obtained from a rotating arm test with a fish model to simulate the navigational performance. Strong points of the navigation system are the elimination of initial position errors and the robustness on the dropout of acoustic signals. The convergence speed and conditions of the initial error removal are examined with Monte Carlo simulation. In addition, numerical simulations are conducted with the six-degrees-of-freedom (6-DOF) equations of motion of an autonomous underwater vehicle (AUV) in a boustrophedon survey mode to illustrate the effectiveness of the integrated navigation system.     

自主回收UUV水声定位与遥测遥控导引技术研究

针对 UUV 任务结束或能源不足时自主回收的需求,深入研究了 UUV 中远程水声定位与遥测遥控导引技术,完成了水声定位与遥测遥控导引系统方案设计,重点研究了 MFSK、OFDM、扩频等水声遥测遥控调制方式。 通过分析和对比,设计了一种正交混合扩频调制方式,并采用相干二维搜索技术,提高扩频技术多普勒补偿能力。 开展了湖上静态与动态跑船试验,试验数据结果表明:水声水平定位精度优于 0. 5%,水声遥测遥控系统解算误码率达到了 10^-3 数量级,可有效引导 UUV 回收作业。     

ADCP对悬浮沉积物浓度的测量及其误差分析研究

为实时、连续地测量海水中悬浮沉积物,利用声学多普勒海流剖面仪(ADCP),可以在测流的同时,测量海洋悬浮沉积物浓度。描述了利用后散射强度,估计悬浮沉积物浓度的原理。在现场测试中,利用采水器采集水样,通过水样分析并结合声信号的衰减特征对AI)CP的测量结果进行修正。作者还结合现场测试结果,对这一测量方法的精度进行了分析。现场实验表明,经公式校正后,ADCP测得的后散射强度与实测水样所获得的悬浮沉积物浓度之间有很好的相关性,相关系数达0．88,由此证明,此测量方法具有很好的实用价值和应用前景。     

Hypothesis grids: improving long baseline navigation for autonomous underwater vehicles

Navigation continues to fundamentally limit our ability to understand the underwater world. Long baseline navigation uses range measurements to localize a remote vehicle using acoustic time-of-flight estimates. For autonomous surveys requiring high precision navigation, current solutions do not satisfy the performance or robustness requirements. Hypothesis grids represent the survey environment capturing the spatial dependence of acoustic range measurement, providing a framework for improving navigation precision and increasing the robustness with respect to non-Gaussian range observations. Prior association probabilities quantify the measurement quality as a belief that subsequent observations will correspond to the direct-path, a multipath, or an outlier as a function of the estimated location. Such a characterization is directly applicable to Bayesian navigation techniques. The algorithm for creating the representation has three main components: Mixed-density sensor model using Gaussian and uniform probability distributions, measurement classification and multipath model identification using expectation-maximization (EM), and grid-based spatial representation. We illustrate the creation of a set of hypothesis grids, the feasibility of the approach, and the utility of the representation using survey data from the autonomous benthic explorer (ABE).     

Installation of ocean bottom bases for observation of seafloor crustal movement

Abstract

Ocean bottom bases (OBBs) have been installed on both sides of the axis of the Sagami Trough east of the Izu Peninsula, central Japan, as the first step toward long‐term geodetic and geophysical observations at the plate boundary (subduction zone). The OBB is a platform for seafloor measurements; otherwise it is difficult to find an appropriate place for precise seafloor measurements in the subduction zones. It is made of a nonmagnetic concrete block of size 1100 × 1100 × 500 mm. It was lowered from a ship using a winch wire and installed on a predetermined place with its position being monitored by an acoustic transponder system and a 30‐kHz bottom pinger with an accuracy of about 2 m.

It was confirmed later during the divings on board the submersible Shinkai 2000 that the OBB was installed on a flat mud bottom in normal condition. No change has been recognized in the installation condition in 3 years; the OBB is stable enough to be used for acoustic range measurements on the seafloor as well as for several geophysical measurements.

The resolution of seafloor range measurement can be improved by two orders by using phase measurement techniques with the aid of pulse compression. Precise acoustic range measurement of the order of 10^?5 is feasible under the following conditions: two‐way measurements between the two OBBs installed on the slope facing each other with angles larger than 1.5°. Correction is necessary for the effect of long‐term temperature variation.     

Active rapid geoacoustic characterization using a seismic survey source

A survey of received acoustic energy levels from a seismic profiler were performed in Long Beach Harbor, CA, for compliance with the Marine Mammal Protection Act (MMPA). In addition to direct acoustic measurements, a rapid geoacoustic inversion algorithm was applied to the data to estimate the sediment properties acoustically. This inversion algorithm has matching criteria based on time spread, range-frequency interference patterns, and the range dependence of transmission loss. Self-consistency was checked by comparing acoustic measurements with predictions based on the inversion. With an estimated geoacoustic profile, predictions of received levels as a function of position in the range-dependent environment of Long Beach Harbor were then performed.     

多波束与单波束测深数据融合处理方法

受声线弯曲的影响,多波束测深的边缘波束的数据质量较低,而单波束测深受声线弯曲的影响比较小。结合多波束覆盖面大和声速剖面误差对单波束影响相对较小的特点,研究了多波束和单波束的测深数据融合方法,利用同一位置单波束和多波束测深数据的差值,拟合一个与坐标位置相关的误差模型,并利用该误差曲面对多波束测深数据进行综合改正,从而提高多波束测深的数据质量。     

多波束测深误差源对测点位置归算影响研究

针对Rob Hare提出的多波束测点位置归算精度估计模型的不足,建立了顾及各项改正数之间相关性的改进模型.在多波束测点位置归算模型的基础上,分析了影响测点位置归算的各项误差来源,推导了各误差源对测点位置归算精度估计的影响量,结合算例,分别利用两种模型计算了各误差源对测点位置归算精度的影响量级,绘制了各误差源的误差曲线图与总位置误差曲线图,通过对计算结果的分析比较,得出了两种模型在评估多波束测点位置归算精度时存在的差异,由于顾及到改正数间的相关性,认为改进模型更加科学合理.     

An adaptive-hybrid algorithm for geoacoustic inversion

This paper presents an adaptive hybrid algorithm to invert ocean acoustic field measurements for seabed geoacoustic parameters. The inversion combines a global search (simulated annealing) and a local method (downhill simplex), employing an adaptive approach to control the trade off between random variation and gradient-based information in the inversion. The result is an efficient and effective algorithm that successfully navigates challenging parameter spaces including large numbers of local minima, strongly correlated parameters, and a wide range of parameter sensitivities. The algorithm is applied to a set of benchmark test cases, which includes inversion of simulated measurements with and without noise, and cases where the model parameterization is known and where the parameterization most be determined as part of the inversion. For accurate data, the adaptive inversion often produces a model with a Bartlett mismatch lower than the numerical error of the propagation model used to compute the replica fields. For noisy synthetic data, the inversion produces a model with a mismatch that is lower than that for the true parameters. Comparison with previous inversions indicates that the adaptive hybrid method provides the best results to date for the benchmark cases     

基于倒置声学基阵的INSUSBL组合导航算法研究

文中关注水下潜航器导航定位时,电磁波传播途径中能量衰减、惯导系统长航时积累误差以及提高水下潜航器定位精度等问题。基于倒置的超短基线声学基阵,分析声波往返传播时间(RTT)、平面波近似方法和USBL导航解算方法及其坐标转换过程,结合INS误差方程,建立INS/USBL松组合模型。为进一步提高系统精度、动态性能和抗干扰性,考察USBL的原始斜距、斜距差以及声学基阵的空间分布信息,提出基于USBL原始输出信息的INS/USBL紧耦合组合导航方法。通过MATLAB仿真对导航算法进行验证,结果表明两种算法能充分抑制纯惯导误差随时间积累问题,且有效地估计出姿态、速度和位置误差角;其中紧耦合方法状态估计误差最小,导航参数精度相对松组合提高30%以上,对于提高水下载体导航定位精度、海洋探测具有重大意义。     

基于单水声信标距离量测的匹配定位方法

水声通信和测距能力是实现水下航行器准确定位的重要技术手段。当前基于水声定位的方法主要有利用测距和测向功能的水声定位技术以及水声测距辅助导航技术,二者的系统物理复杂度都比较高。本文提出了一种基于单水声信标距离量测的匹配定位方法,航行器在水声信标测距覆盖范围内,利用航行过程中多次测距信息构建测距圆序列形成位置约束,基于航位推算导航信息,将航行器在连续测距时间段内的相对航迹在圆序列上进行最优匹配,从而获得位置估计,通过对测距误差进行补偿可进一步提升定位精度。本方法所需物理系统结构复杂度低、可操作性强,仿真实验表明,该方法可以独立实现较高精度的定位。     

Localization of autonomous underwater vehicles by floating acoustic buoys: a set-membership approach

This paper addresses localization of autonomous underwater vehicles (AUVs) from acoustic time-of-flight measurements received by a field of surface floating buoys. It is assumed that measurements are corrupted by unknown-but-bounded errors, with known bounds. The localization problem is tackled in a set-membership framework and an algorithm is presented, which produces as output the set of admissible AUV positions in a three-dimensional (3-D) space. The algorithm is tailored for a shallow water situation (water depth less than 500 m), and accounts for realistic variations of the sound speed profile in sea water. The approach is validated by simulations in which uncertainty models have been obtained from field data at sea. Localization performance of the algorithm are shown comparable with those previously reported in the literature by other approaches who assume knowledge of the statistics of measurement uncertainties. Moreover, guaranteed uncertainty regions associated to nominal position estimates are provided. The proposed algorithms can be used as a viable alternative to more traditional approaches in realistic at-sea conditions.     

Forward Scattering From a Rippled Sand/Water Interface: Modeling, Measurements, and Determination of the Plane Wave, Flat Surface Reflection Coefficient

In this paper, modeling results are presented demonstrating that, using an ensemble of forward-scattering measurements from a rippled sand/water interface, it is possible to accurately estimate the plane wave, flat surface reflection coefficient. The modeling effort was carried out in preparation for a sediment acoustics experiment in 2004 (SAX04). Guided by the modeling results, forward-scattering measurements were made during SAX04. The measurement instrumentation and procedure are presented. The plane wave reflection coefficients derived from these measurements are given and compared to reflection coefficients calculated using a fluid model and an approximation to the Biot porous medium model for the sand known as the effective density fluid model (EDFM). The model reflection coefficients were calculated using acoustic parameters determined from environmental measurements carried out by other researchers involved in SAX04. The reflection coefficient data/model comparison indicates that the sand at the SAX04 site is most accurately viewed as a porous medium for acoustic modeling purposes.      

A study of increasing the precision of navigation position for submerged body

Currently, most submerged bodies use the long-baseline acoustic position system (LBL) to identify the navigation position for submerging. A precise navigation position is always the target pursued by underwater technology. The conventional long-baseline acoustic position systems normally use Kalman filter correction to handle the problem of positional errors. This article proposes a new modification, which is based on the periodically measured actual navigation distance, and associated with the three-dimensional geometrical relations between the transponder on the seabed and the navigation distance. This new modification employs the iterative approximation to modify the errors of the measured navigation position from the conventional long-baseline acoustic position system. In order to verify the availability of the modified model by the essay, the study uses the navigation position for an underwater surveying submerged body as the study object. After the numerical simulation analysis, the result shows that the modification was presented by the article can only use very few iterations to precisely modify the errors of the measured navigation position from the conventional long-baseline acoustic position system, which is highly applicable for positioning in long-term and long-distance submersion. Moreover, the modification method proposed by the paper can also help submersion positioning for the underwater vehicle, as well as the military submerged body.     

高浓度悬浮泥沙的声学观测

在分析高浓度悬浮泥沙的声衰减机理和进行实验研究的基础上,研制了两种型号的超声波观测仪器(UBD-500/1500超声重度计)用于悬浮泥沙浓度剖面的连续和实时观测,并且已经在长江口航道的浮泥探测、黄河小浪底水库的泥沙观测中得到应用.讨论了测量原理和仪器的设计、标定等问题.这种基于声衰减测量原理的观测仪器的主要优点是标定简便和稳定,含沙量观测范围为10～800kg/m3,标定后的测量误差可达±5%(F.S).     

Deep Sea AUV Navigation Using Multiple Acoustic Beacons

Navigation is a critical requirement for the operation of Autonomous Underwater Vehicles (AUVs). To estimate the vehicle position, we present an algorithm using an extended Kalman filter (EKF) to integrate dead-reckoning position with acoustic ranges from multiple beacons pre-deployed in the operating environment. Owing to high latency, variable sound speed multipath transmissions and unreliability in acoustic measurements, outlier recognition techniques are proposed as well. The navigation algorithm has been tested by the recorded data of deep sea AUV during field operations in a variety of environments. Our results show the improved performance over prior techniques based on position computation.     

嵌入式硬件在环UUV模拟器的设计及实现

针对 UUV 对高逼真仿真的需求,设计了嵌入式硬件在环 UUV 模拟器。 选用 XMC4800 作为模拟器的主控芯片,设计了最小系统电路和通信接口电路。 给出了数据流图和主要软件算法,包含任务调度算法、任务优先级设计、UUV 模型选择、干扰模型选择和 CAN 应用层协议设计。 模拟器具有多种工作模式, 可以根据不同的应用场景,完成相应的硬件在环仿真,对 UUV 的研制、生产和使用具有一定的参考价值。     

Experimental study of the ballast in situ sediment acoustic measurement system in South China Sea

The mechanical structure, the function modules, the working principles, and a sea trial of the newly developed ballast in situ sediment acoustic measurement system are reported in this study. The system relies on its own weight to insert transducers into seafloor sediments and can accurately measure the penetration depth using a specially designed mechanism. The system comprises of an underwater position monitoring and working status judgment module and has two operation modes: self-contained measurement and real-time visualization. The designed maximum working water depth of the system is 3,000?m, and the maximum measured depth of seafloor sediment is 0.8?m. The system has one transmitting transducer with the transmitting frequency band of 20–35?kHz and three receiving transducers. The in situ acoustic measurement system was tested at 15 stations in the northern South China Sea, and repeated measurements in seawater demonstrated good working performance. Comparison with predictions from empirical equations indicated that the measured speed of sound and attenuation fell within the predicted range and that the in situ measured data were reliable.     

一种基于伽利略搜救系统的联合定位算法

分析了伽利略搜救系统的地面站定位模型。提出了一种适用于该系统的,在存在多余观测的情况下,基于信号的时间延迟和多普勒频率测量值加权后,共同参与平差计算的联合定位算法模型及其误差分布模型。仿真结果表明,与单纯使用一种观测值的定位算法相比,该算法可以提高定位精度,是一种适合伽利略搜救地面站使用的定位算法。     

Measurement of Ocean Surface Currents by the CRL HF Ocean Surface Radar of FMCW Type. Part 2. Current Vector

The Communications Research Laboratory (CRL) has been developing high-frequency ocean surface radars (HFOSRs). The CRL dual-site HFOSR system can clarify the distribution of surface currents with a nominal range of 50 km. This paper presents a theoretical and experimental analysis of the measurement error of the current vector obtained by the CRL HFOSR system, using a comparison of instantaneous current vectors acquired by the HFOSR system and current meters moored at a depth of 2 m, taking account of the vertical current shear. The theoretical analysis shows that the probability distribution of the measurement error of the current vector forms concentric ellipses at a spatial scale that depends on the RMS measurement error of radial current velocity and with an aspect ratio that depends only on the azimuthal difference of the radar beams. When the azimuthal difference is a right angle, the measurement error of the current vector is at a minimum. A comparison between instantaneous current vectors measured by the CRL HFOSR system and moored current meters shows that the distribution of the difference vector between the radar current and the meter current agrees well with the theoretical measurement error of the current vector and that the RMS of difference vector length is about 10 cm s^–1 while the azimuthal difference between two radar beams is between 45 and 135 degrees. The accuracy of current measurement by the dual-site HFOSR system is therefore considered to be less than 10 cm s^–1 in this range of azimuthal difference. The theoretical analysis will be applicable for a wider range of the azimuthal difference of the radar beams.