Research for enhancing the precision of asymmetrical SBL system for any vessels

The SBL system (Short Baseline System) is usually utilized by offshore working vessels when performing its underwater orientation task so as to facilitate the exploitation of abundant benthal resources, therefore, the precise distance between the vessel and underwater targets for SBL system's estimation module are highly emphasized. However, hydrological data cited in the SBL system's estimation module is not real-time information and is difficult to accurately measure, which causes the calculation errors. Studies with regard to symmetrical SBL system are carried out by most of the researchers these days, yet research in this text shows the advantage to the asymmetrical SBL system's sensor on the vessel's bottom to be installed at discretion to measure and calculate the position. In addition to the locus equation used in the traditional position calculation, Haussiam Elimination, Cramer's rule, 3D geometry relation theory as well as substitution corrections applied to this asymmetrical SBL system to educe the correction for relative geometrical position between the underwater beacon and the sensor on the ship bottom. Through numeric simulation analysis, this SBL system is proved to be a high precision acoustic positioning system based on its quick correction and high precision position calculated by the asymmetrical SBL system established in this study.     

Real-Time Adjustment Underwater Positioning System for Submarines

A rapid real-time adjustment scheme is proposed for improving the precision of the conventional short-base line (SBL) positioning fix system used by submarines and other underwater vehicles. In the proposed approach, an initial position estimate is obtained by solving the conventional SBL tracking equations of the submarine given the assumptions of a constant speed of sound in water and a straight-line propagation path. In the first stage of the real-time adjustment procedure, this initial estimate is corrected using an iterative computation scheme based on a 3D geometry model. The improved position estimate is then used to compute a new, more accurate value of the speed of sound in water. Finally, in the second stage of the real-time adjustment procedure, the corrected speed of sound in water and the discrepancy between the original and corrected position estimates obtained in the first adjustment procedure are applied to update the coordinates of the submarine based on the second signal received from the pinger. The numerical results show that the proposed real-time adjustment system yields a significant improvement in the accuracy of the positioning fix estimates compared to those obtained from the conventional SBL method or the SBL method with the first adjustment procedure only.     

一种低功耗海洋定位信标的研制与应用

研制了一种低功耗的定位信标,用于长期服役于水下的海洋仪器回收出水后的定位搜寻工作。信标基于GPS射频组件开发,与仪器固定在一起,待整体浮出水面后,会启动位置信号发送程序,通过电信网络,将该信标的实时位置发送至终端。经测试表明,信标性能可靠,可为海洋仪器的安全工作和顺利回收提供保障。     

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。     

Robust Range-Only Beacon Localization

In this paper, we present a system capable of simultaneously estimating the position of an autonomous underwater vehicle (AUV) and the positions of stationary range-only beacons. Notably, our system does not require beacon positions a priori, and our system performs well even when range measurements are severely degraded by noise and outliers. We present a powerful outlier rejection method that can identify groups of range measurements that are consistent with each other, and a method for initializing beacon positions in an extended Kalman filter (EKF). We have successfully applied our algorithms to real-world data and have demonstrated a simultaneous localization and mapping (SLAM) system whose navigation performance is comparable to that of systems that assume known beacon locations     

A high-resolution pulse-Doppler underwater acoustic navigation system

A high-resolution underwater acoustic pulse-Doppler navigation system has been developed and tested at sea. The system provides continuous, highly accurate tracking of underwater and ocean-surface platforms in a fixed 50-km²navigation net. Three reference buoys, moored 20 m from the ocean bottom, provide the navigation net used by shipboard processing equipment. Each reference buoy contains an acoustic transponder, used to obtain the acoustic travel times from the transponder to the platform, and a continuous-tone beacon, used to obtain the Doppler shift due to platform motion. The system is capable of determining the position of a platform with respect to the reference net with an error of 2-3 m. The relative position of the platform on a fix-to-fix basis can be determined within several centimeters over short time intervals (approx 10min).     

海洋测量水下拖曳设备的位置计算方法研究

针对海洋测量水下拖曳设备位置确定问题,综合考虑拖缆受力、海流影响以及水下拖体的运动性质,建立了水下拖曳设备的位置计算模型,并仿真计算分析了测量船在不同航行状态下拖曳设备位置确定的规律,探讨了不同海流效应对拖曳设备位置确定的影响。仿真计算结果表明,在海洋动态环境作用下,拖缆各方向的偏移明显呈曲线形状,非简单几何运算所确定。测船各方向的运动均可对水下拖体的位置在相应方向产生一定影响,而水下拖体位置的变化量小于测船拖点位置的变化量。海流对水下拖曳设备定位可造成数米的偏差,需进行相应改正。建议可考虑采取船载式ADCP实时测流辅助水下拖曳设备定位的工作模式。     

基于高阶滑模控制器的水下潜器运动控制

水下环境复杂多变,由于水流的不可预知性和多变性,潜器的水动力系数往往无法准确获取,使得依赖这种参数的潜器运动控制算法的应用受到了很大的局限。为了解决控制器对模型参数的依赖,设计了一种基于高阶滑模控制算法的模型无关控制器,并通过设置合理的过渡过程,解决了这种控制算法依赖初值的弊端。仿真结果表明,位置和姿态的控制能够快速的收敛,误差很小并且不依赖于初始条件,控制器需调节参数很少,并且算法简单,适用于工程的实际需要。     

Underwater Navigation Based on Real-Time Simultaneous Sound Speed Profile Correction

Precise sound speed profile (SSP) information is critical when using sonar for underwater terrain navigation. Nevertheless, acquiring SSP information in real-time is difficult, especially in underwater navigation environment. To account for this problem, this paper presents an underwater navigation method that applies real-time SSP correction to the terrain measurements. The method uses a probe to measure the surface sound speed simultaneously. Meanwhile, redundancy of topographic measurement data is exploited to derive the equivalent SSP information. The acquired equivalent SSP is updated continuously with particle filter algorithm. The terrain measurements can be corrected in real-time with the equivalent SSP to improve the performance of underwater terrain navigation. By removing the impact of inaccurate SSP from the terrain measurements, the proposed method can achieve precise and robust underwater navigation result without using an underway-profiling instrument. Simulated results confirm the good performance of the proposed method.     

Autonomous underwater vehicles - challenging developments and technological maturity towards strategic swarm robotics systems

ABSTRACT

Reliable power supply, precise position determination and effective communication are the key requirements for strategic autonomous underwater vehicles (AUV) involved in long duration scientific missions, search operations and when operated as a swarm. The paper presents the challenging range of AUV developed for deep water, Polar and intervention applications; demanding technical requirements for strategic AUV; reliability modeling done on the lithium-ion batteries to identify the redundancy requirements for achieving near-zero failures; navigation model to estimate the achievable level of position accuracies using the state-of-the-art navigation system; limitations in underwater communication; and their importance in realizing vehicle autonomy and swarm intelligence. It is identified that a strategic grade Doppler velocity- aided inertial navigation system could provide position accuracies of about 0.5% of the distance travelled when navigated using sea bottom or ice reference, and a 38?kWh lithium-ion battery pack requires about 7% redundant battery capacity to achieve a failure probability of <?1% in a period of 1 year.     

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.     

基于ICCP匹配算法的海底地形匹配辅助导航

利用海底地形辅助导航是水下载体导航技术致力研究的新方向,采用ICCP算法作为对准匹配算法,利用实测地形数据和已知地形数据库,进行仿真计算,修正惯性导航系统累计误差,得到水下载体的最佳匹配位置,以提高水下载体的导航精度。     

Survey of underwater robot positioning navigation

Underwater robot positioning and navigation achieve autonomous underwater robot movement based on the premise that positioning obtains the coordinates of the relative position of the underwater robot using a sensor, and navigation yields a known location to the destination path planning. Due to the location of an underwater robot and the complex and changing environment in which it operates, it is difficult to achieve precise positioning using the traditional positioning method. This paper systematically analyzes and summarizes several typical localization and navigation methods of underwater robots, such as multisensor information fusion technology, underwater acoustic localization and navigation methods, GPS buoy, underwater vision, SLAM and coordinate localization and navigation of multiple underwater robots. Multisensory information fusion technology integrates the advantages of the above methods, enhances the system stability and robustness, overcomes the disadvantages of traditional positioning and navigation, and enables the autonomous navigation and positioning of underwater robots. Underwater acoustics enable flexible and convenient positioning, whereas GPS can achieve high-precision and high-positioning navigation information, and visual positioning effectively overcomes the problem of error accumulation. Multirobot cooperative positioning resolves the problem of positioning failure caused by the collapse of a single system and completes complex tasks that cannot be completed by a single robot, thus enhancing the stability and robustness of the system. This paper systematically describes the realization of these methods, presents an actual analysis of their respective advantages and problems, and discusses the development of the field of research prospects and application prospects.     

基于GNSS方位辅助惯性导航系统的水下地形精密测量技术

多波束测深技术是目前水下地形测量的主要技术手段,测量平台的瞬时姿态及方位是影响多波束测深系统最终成果准确度的重要因素。GNSS方位辅助惯性导航系统,作为目前应用较为广泛的方位、姿态、及位置综合测量系统,不仅能够提供高精度位置信息,同时也能提供测量平台的瞬时姿态及方位数据,而且因为具有GNSS方位辅助测量,使得最终方位测量结果比传统方位测量精度大大提高,这对于多波束最终测量成果精度提高具有重要意义。文中从GNSS方位辅助惯性导航系统原理及技术优势出发,结合Trimble RTX后处理技术,从姿态测量、方位测量及辅助高程测量方面分析了在多波束水下地形测量中的应用,并以实际测量成果来展现其在水下地形精密测量技术方面的优势,结果显示,定位精度可以达到优于2 cm级别,方位精度可以优于0.01°(依赖于双GNSS天线之间的基线长度),该技术对水下地形测量准确度提升作用显著。     

Accurate current measurement using drogued buoys employing DeccaNavigator and Argos

Free-floating drogued buoys have been developed for detailed studies of tidal processes, frontal circulation, eddies, and mixing in the North Sea. They are equipped with two independent tracking systems-Decca Navigator and Argos. Decca Navigator, a hyperbolic radio navigation system with extensive coverage in Western Europe, provides accurate and frequent fixes, and the Argos satellite system is used to monitor progress in real time and to assist recovery. The low power consumption microprocessor-based Decca Navigator receiver designed specifically for this application synchronizes to the precisely timed Decca transmission and then goes into sleep mode, waking briefly at 10-min intervals to take position fixes. The position data are stored in a 2-Mb memory card that has a three-month capacity at the 10-min rate. The recovery procedure, using both Argos and a small VHF beacon, is described, together with other recent developments. A typical buoy track from a study in the North Sea is included     

基于北斗定位导航系统的水下监测平台出水报警定位信标机设计与实现

由于海洋内部环境复杂多变,加之渔业捕捞作业范围和深度的逐步扩大,对水下监测平台的安全构成了极大威胁。而且,在水下平台的海上回收作业过程中,恶劣海况、海雾、海面光反射等不利因素无不给回收过程造成很大麻烦,一旦平台浮出海面后漂出视距范围,将面临丢失风险。文中借助北斗定位导航系统,结合压力检测电路,设计并实现了一种可用于水下平台意外出水报警、出水后实时定位的卫星定位信标机系统,经多次应用,证明性能稳定可靠。     

Underwater Terrain Positioning Method Based on Least Squares Estimation for AUV

To achieve accurate positioning of autonomous underwater vehicles, an appropriate underwater terrain database storage format for underwater terrain-matching positioning is established using multi-beam data as underwater terrainmatching data. An underwater terrain interpolation error compensation method based on fractional Brownian motion is proposed for defects of normal terrain interpolation, and an underwater terrain-matching positioning method based on least squares estimation(LSE) is proposed for correlation analysis of topographic features. The Fisher method is introduced as a secondary criterion for pseudo localization appearing in a topographic features flat area, effectively reducing the impact of pseudo positioning points on matching accuracy and improving the positioning accuracy of terrain flat areas. Simulation experiments based on electronic chart and multi-beam sea trial data show that drift errors of an inertial navigation system can be corrected effectively using the proposed method. The positioning accuracy and practicality are high, satisfying the requirement of underwater accurate positioning.     

Underwater Terrain Positioning Method Based on Least Squares Estimation for AUV

To achieve accurate positioning of autonomous underwater vehicles, an appropriate underwater terrain database storage format for underwater terrain-matching positioning is established using multi-beam data as underwater terrain-matching data. An underwater terrain interpolation error compensation method based on fractional Brownian motion is proposed for defects of normal terrain interpolation, and an underwater terrain-matching positioning method based on least squares estimation (LSE) is proposed for correlation analysis of topographic features. The Fisher method is introduced as a secondary criterion for pseudo localization appearing in a topographic features flat area, effectively reducing the impact of pseudo positioning points on matching accuracy and improving the positioning accuracy of terrain flat areas. Simulation experiments based on electronic chart and multi-beam sea trial data show that drift errors of an inertial navigation system can be corrected effectively using the proposed method. The positioning accuracy and practicality are high, satisfying the requirement of underwater accurate positioning.     

A precise and continuous monitoring system of the distance between the near-bottom instruments and the sea floor

A relatively simple and inexpensive distance monitoring system (DMS) was devised to monitor continuously and accurately the position of an underwater camera with an attached pinger relative to the sea floor. Although the precision graphic recorder (PGR) or precision depth recorder (PDR) have hitherto been used to record the pinger to bottom distance, these complicated and expensive instruments are not always expected on all vessels.This newly developed system, which measures with a counting timer the interval between the direct sound pulses generated by a pinger and the bottom echoes, yielded results equal to or better than that of the PGR. The distance information thus obtained was accurate within ±2.5% under good conditions (calm weather and flat and level topography) just above the sea bed. This system simplified the photographing operations and made it possible to obtain a precise and quantitative assessment of the epibenthic fauna with the use of a single camera.The DMS is also applicable for determining the precise location of a bottom water sampler, grab sampler, or other underwater oceanographic equipment as well as that of an underwater camera.A part of this research was supported by science research fund from the Ministry of Education.     

适用于中国近海观测研究浮标的北斗/GPS双模信标系统的研制与应用

为了提高海洋观测研究浮标在位运行的安全性,自主设计了一种北斗/GPS双模定位信标。该信标采用传统的GPS技术进行定位结合“北斗”卫星特有的报文通信和定位功能,通过解决传统GPS信号盲区问题,为中国近海海洋观测研究浮标安全运行提供了更加有力的保障,同时提高了数据保密能力。该系统采用外部供电和内部自主供电相结合的模式,即使外部供电中断,也可保证正常运行不低于1 a,而且基本上不需要对信标进行专门维护,大大降低了运行和维护成本。与该信标配套的岸站管理系统具备发送和短信和邮件报警的功能,可实现浮标运行状态实时监控。