共查询到20条相似文献，搜索用时 31 毫秒
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Yan-bo Wu Min Zhu Tao Liang Wei Wang Bo Yang Lin-yuan Zhang Xin-guo Li Ye-yao Liu 《中国海洋工程》2018,32(6):746-754
The Shipborne acoustic communication system of the submersible Shenhai Yongshi works in vertical, horizontal and slant channels according to the relative positions. For ease of use, an array combined by a vertical-cone directional transducer and a horizontal-toroid one is installed on the mothership. Improved techniques are proposed to combat adverse channel conditions, such as frequency selectivity, non-stationary ship noise, and Doppler effects of the platform’s nonlinear movement. For coherent modulation, a turbo-coded single-carrier scheme is used. In the receiver, the sparse decision-directed Normalized Least-Mean-Square soft equalizer automatically adjusts the tap pattern and weights according to the multipath structure, the two receivers’ asymmetry, the signal’s frequency selectivity and the noise’s spectrum fluctuation. The use of turbo code in turbo equalization significantly suppresses the error floor and decreases the equalizer’s iteration times, which is verified by both the extrinsic information transfer charts and bit-error-rate performance. For noncoherent modulation, a concatenated error correction scheme of nonbinary convolutional code and Hadamard code is adopted to utilize full frequency diversity. Robust and low-complexity synchronization techniques in the time and Doppler domains are proposed. Sea trials with the submersible to a maximum depth of over 4500 m show that the shipborne communication system performs robustly during the adverse conditions. From the ten-thousand communication records in the 28 dives in 2017, the failure rate of the coherent frames and that of the noncoherent packets are both below 10%, where both synchronization errors and decoding errors are taken into account. 相似文献
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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 10 min). 相似文献
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This paper presents a method for tracking a distant moving target using only bearing measurements obtained from a tracking platform. The method is an improvement of the Hinich-Bloom passive tracking approach presented in [1]. The target is assumed to be moving at constant speed on a fixed heading, whereas the platform maneuvers during the measurement period. The direction cosines of the bearings are computed with respect to a rotation of the coordinate system that places 0° at the mean estimated target bearing. This is done to minimize the approximation bias due to the linearization of sine bearing as a function of inverse range and time. The coordinate system is rotated back to estimate the target coordinates. When the noise is Gaussian, the estimates of target range and heading are approximately maximum likelihood when the target's relative range is slowly varying during the observation period. In this case the mean square errors of the target parameter estimates are the smallest achievable within the order of the approximation. 相似文献
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A method of extracting wave parameters from surface displacement measured from a moving platform is presented. The article first presents a method for accurately measuring surface displacement using a single beam altimeter and heave sensor. A least squares approach is presented to estimate wave parameters using vessel velocity and perceived wave frequency that eliminates Doppler due to vessel motion. Two techniques for estimating wave frequency are presented: a block data method using MUSIC and a real-time method using demodulation. Sea trial results demonstrate that this method is as effective as a WaveRider buoy for estimating wave parameters. 相似文献
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Multicarrier Communication Over Underwater Acoustic Channels With Nonuniform Doppler Shifts 总被引：3，自引：0，他引：3
《Oceanic Engineering, IEEE Journal of》2008,33(2):198-209
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The autonomous underwater glider "Spray" 总被引：4，自引：0，他引：4
A small (50-kg, 2-m long) underwater vehicle with operating speeds of 20-30 cm/s and ranges up to 6000 km has been developed and field tested. The vehicle is essentially an autonomous profiling float that uses a buoyancy engine to cycle vertically and wings to glide horizontally while moving up and down. Operational control and data relay is provided by GPS navigation and two-way communication through ORBCOMM low-Earth-orbit satellites. Missions are envisioned with profile measurements repeated at a station or spaced along a transect. The initial instrument complement of temperature, conductivity, and pressure sensors was used to observe internal waves and tides in the Monterey underwater canyon 相似文献
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This paper is part of a series of three papers studying passive tracking problems arising in navigation and positioning applications. The basic question here lies with the determination of the position and dynamics of a point source being tracked by an omnidirectional observer, through demodulation of the Doppler effect induced on the radiated signals by the relative motions. A simple model, fitting a finite parameter nonlinear estimation context, is developed, the receiver designed, and its mean-square error performance studied. It is shown that, besides the speed and angle estimation, simultaneous global range passive tracking is possible. The signal model precludes range acquisition from synchronous measurement of the absolute phase reference: the global range estimation is attained by processing the higher order temporal modulations (varying Doppler). Quantifying the statistical and geometric performance tradeoffs, the work presents simple expressions and graphical displays that can be used as design tools in practical passive tracking problems. A subsequent paper considers the space/ time coupling issues, generalizing the study to the context where a moving source is tracked by a directional array. 相似文献
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疲劳破坏是海洋结构物发生破坏的一种主要形式,深水半潜平台在海上运输、作业、停滞时会受到交变的风、浪、流载荷作用,进而引起结构关键节点处的疲劳损伤,影响平台安全性。以"海洋石油981"半潜钻井平台为研究对象,利用光纤光栅应变传感器对结构高应力区进行应力监测,获取测点处应力时历数据。将监测位置划分为四个监测板块,采用四点雨流计数法对测点应力进行处理,得到以离散形式给出的应力循环幅度与相应循环周次。参照DNV《海上钢结构疲劳设计规范》推荐的S-N曲线,基于Miner线性疲劳累计损伤原则,得到各个测点处的总体疲劳损伤度。选取具有最大疲劳损伤度的危险测点,并结合海上实测总时长,预测半潜平台的总体疲劳寿命。 相似文献
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Measurements are reported from two side-looking Doppler systems, which were used to study the discharge front located off the mouth of Chesapeake Bay. One system was a commercial 300-kHz narrow-band acoustic Doppler current profiler (ADCP), which was mounted at a depth of 0.6 m on the port side of a research ship. The other was a prototype X-band, vertically polarized, Doppler radar mounted at a height of about 4 m on the starboard side. Both velocity and backscatter intensity were measured along two beams to ranges of 120 m (ADCP) and 200 m (radar), so that by sailing alternately on each side of the front it was possible to make nearly simultaneous across-front measurements with both systems. Despite the differences in acoustic and radar scattering mechanisms, a combined backscatter intensity surface map could be made showing a continuous frontal signature about 10-m wide and 20 dB above background levels. Each system was also able to measure the same large-scale velocity change across the front, which was dominated by the discharging buoyant bay water flowing at about 50 cm/s relative to the ambient continental shelf water. However, within a 60-m wide zone, the radar system measured velocities up to 75 cm/s larger than the ADCP. Such large velocity differences arose from the radar's sensitivity to motions associated with waves reflecting from the region of strongest across-front current convergence. This frontal convergence was resolved only by the ADCP, which showed a horizontal current change of about 25 cm/s over 10 m and appeared to extend over the upper 2 m or so of the water column. These results show that the combined information from the acoustic and radar systems provide a more complete picture of the frontal currents and wave-current interactions than either system could provide alone 相似文献
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Various parameters associated with the track of a stable CW source moving with constant velocity are estimated using synthetic aperture and Doppler processing techniques. These include the source frequency before Doppler distortion by its motion, the relative speed between the source and a constant velocity receiver, the range at closest approach to the source track, and the relative bearing to the source. Different processing techniques are suggested for a range of signal stabilities and observation times. Frequency analysis, or Doppler processing, supplements conventional synthetic aperture processing, and for relatively unstable signals a synthetic Doppler method is recommended. This method makes use of a rapid scan of signals from a succession of sensors in a horizontal line array to stimulate a higher speed motion of the array 相似文献
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从国家安全、海洋开发、监测平台的发展需求方面,阐述了深海监测平台对深海环境监测的意义,以及国内外的发展现状,提出了一种新型的深海监测平台,即深海通讯浮标蜂窝集装式传输平台,概述了该平台系统工作过程,并对其结构、功能,以及各组成系统的作用进行了详细的论述。 相似文献
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《Oceanic Engineering, IEEE Journal of》2009,34(3):294-306
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一个水声扩频通信系统设计与实现 总被引：2，自引：0，他引：2
严重的多途衰落、多普勒频偏是水声通信中引起误码的主要原因。低功耗、远距离、高隐蔽性、低信噪比检测、高可靠性的数据传输是水声通信的一个发展方向。设计并实现了一个水声扩频通信系统,有效地解决了以上问题,并采用快速相关算法,代替传统的矢量与矩阵相乘运算,极大地减少了程序的运行量,从而实时地处理接收信号。通过湖试和海试,验证了此通信系统的优良性能。 相似文献
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An oceanic reverberation model 总被引：1，自引：0，他引：1
A simple model of the surface, volume, and bottom reverberation received by a moving platform as a function of time following the tranmission of a narrow-band pulsed signal is described. Both the time-varying power level and the underlying power spectrum are predicted. The model includes the effects of platform motion, transmit signal windowing, transmit and receive beam patterns, and the environment (surface, volume, and bottom backscattering strengths, the scatterer velocity distributions for surface waves and current layers, and sound absorption). An isospeed sound speed profile is assumed and reflections at the surface and bottom boundaries are not permitted. Also described is a matched filter-envelope detector receiver model for post processing of the reverberation spectra. 相似文献
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一种适用于水声通信的Doppler估计算法 总被引：1，自引：0，他引：1
在水下声通信中,收发双方相对运动产生的Doppler效应会导致信号的伸缩,引起信噪比的降级,需要采用Doppler补偿措施。在补偿前需要得到Doppler估计。文中提出了一种利用DFT进行Doppler估计的有效算法,该算法通过估计频率偏移来计算Doppler率。仿真结果验证了该算法的有效性。 相似文献
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Lipa B.J. Barrick D.E. Isaacson J. Lilleboe P.M. 《Oceanic Engineering, IEEE Journal of》1990,15(2):119-125
CODAR, a high-frequency (HF) compact radar system, was operated continuously over several weeks aboard the semisubmersible oil platform Treasure Saga for the purpose of wave-height directional measurement and comparison. During North Sea winter storm conditions, the system operated at two different frequencies, depending on the sea state. Wave data are extracted from the second-order backscatter Doppler spectrum produced by nonlinearities in the hydrodynamic wave/wave and electromagnetic wave/scatter interactions. Because the floating oil rig itself moves in response to long waves, a technique has been developed and successfully demonstrated to eliminate to second order the resulting phase-modulation contamination of the echo, using separate accelerometer measurement of the platform's lateral motions. CODAR wave height, mean direction, and period are compared with data from a Norwegian directional wave buoy; in storm seas with wave heights that exceeded 9 m, the two height measurements agreed to within 20 cm RMS, and the mean direction to better than 15° RMS 相似文献
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The swell of a moving typhoon has the same Doppler effect as a moving sound source. Both originate from the variations in an energy flux. In a sound source this is called a frequency shift. In a typhoon it is a swell wave height change. A distant typhoon may generate very high waves through the Doppler effect as the typhoon approaches. A modification λ is proposed for engineering practice. 相似文献