共查询到20条相似文献，搜索用时 644 毫秒
1.
Bearings-only target motion analysis is a nonlinear state estimation problem in which the noise corrupted angle of arrival measurements of an emitted signal are used to obtain estimates of the source's range, bearing, course, and speed. The estimation process is complicated by unusual observability properties that render the quality of the estimate highly dependent on both the measurement noise levels and the source-observer geometry. Solutions that use recursive Kalman filtering approach or batch-style algorithms have been reported. The nonlinear batch style estimators for this process require iterative solution methods and under certain scenarios can be sensitive to initial conditions. Pseudolinear solutions that alleviate some of the difficulties with the iterative batch algorithms have been proposed. Although early versions of the pseudolinear filter suffered from biased estimates, subsequent improvements appear to have reduced the bias problem. This paper discusses a new pseudolinear solution based on the observable parameters from individual data segments defined by periods of constant observer velocity (termed “legs”). This solution is a true closed-form solution to the bearings-only target motion analysis problem. Although theoretically interesting, the technique does suffer under conditions of poor observability. A practical pseudolinear estimate, that does not suffer from the same observability problems, is developed and related to the first solution. Algorithm performance results, obtained from computer simulation, are presented. For the scenarios examined, the technique provides good state estimates under conditions of high observability. As observability conditions deteriorate, the solution does develop biases. However, it may still be useful for initializing an iterative nonlinear batch-style estimation algorithm 相似文献
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3.
《Oceanic Engineering, IEEE Journal of》2008,33(2):182-197
4.
Dynamic positioning (DP) is an operation method whereby the position of a surface vessel is maintained in close proximity to a required position in the horizontal plane through the controlled application of forces and moments generated by purposely installed thrusters. When estimating thrust, this kind of conventional control system often uses many acceleration sensors, velocity sensors, environment sensors, and filters. Usually, these sensors have measured electrical errors. To reduce the number of sensors used and to decrease the measurement errors, this article presents an effective control system for estimating thrust and moment commands, which is based on energy and impulsemomentum principles. Donha and Brinati's example is followed to verify the feasibility of the present control system, which performs semisubmersible platform positioning using an LQG controller, and the results are feasible and economical. A simulated coring vessel marine positioning in southern Taiwan is presented, which can estimate the counterthrust and moment commands, and the complex environmental forces and moments are described. The results can provide a valuable control system for dynamically positioned vessels. 相似文献
5.
Dynamic positioning (DP) is an operation method whereby the position of a surface vessel is maintained in close proximity to a required position in the horizontal plane through the controlled application of forces and moments generated by purposely installed thrusters. When estimating thrust, this kind of conventional control system often uses many acceleration sensors, velocity sensors, environment sensors, and filters. Usually, these sensors have measured electrical errors. To reduce the number of sensors used and to decrease the measurement errors, this article presents an effective control system for estimating thrust and moment commands, which is based on energy and impulsemomentum principles. Donha and Brinati's example is followed to verify the feasibility of the present control system, which performs semisubmersible platform positioning using an LQG controller, and the results are feasible and economical. A simulated coring vessel marine positioning in southern Taiwan is presented, which can estimate the counterthrust and moment commands, and the complex environmental forces and moments are described. The results can provide a valuable control system for dynamically positioned vessels. 相似文献
6.
Methods for joint ocean-channel estimation and data recovery are derived using an optimal, maximum likelihood (ML) estimation criterion. The resulting ML problems may be complex, thus iterative algorithms are used, e.g. the expectation-maximization (EM) algorithm. The different methods correspond to different assumptions about the ocean channel. The theoretical derivation of these methods as well as preliminary results on simulated ocean data experiments are presented 相似文献
7.
Reliable analysis of stability and safety level in a flooding emergency onboard a damaged passenger ship is extremely important for making correct decisions on evacuation and abandonment. Thus there is demand for an automated system that detects flooding and analyzes the severity of the situation. This procedure requires estimation of the actual breach in the hull, and calculation of possible progressive flooding to undamaged compartments. A new approach to the breach assessment, based on measurement data from the flood level sensors, is presented. The developed method is complemented by time-domain flooding simulations in order to separate progressive flooding from direct inflow through the breaches in the hull of the damaged ship. The developed approach is tested and demonstrated with a large passenger ship design for various damage scenarios. The results show that the size and location of the breach can be evaluated with reasonable accuracy on the basis of the level sensor data, provided that there are enough well-placed, working level sensors. 相似文献
8.
Dosso S.E. Brooke G.H. Kilistoff S.J. Sotirin B.J. McDonald V.K. Fallat M.R. Collison N.E. 《Oceanic Engineering, IEEE Journal of》1998,23(4):365-379
Array element localization (AEL) surveys are often required to accurately localize acoustic instruments (transponders or sensors) in the ocean. These are typically based on transmitting or recording acoustic signals from or at a set of well-known positions. A significant limiting factor in many AEL surveys is the uncertainty inherent in these “known” positions. In this paper, an inversion algorithm is developed which properly treats both transponder and sensor positions as unknowns, subject to available a priori information in the form of position estimates and uncertainties. The algorithm essentially consists of an iterative linearized inversion of the raytracing equations employing the method of regularization. The approach is applied to independently localize transponders and vertical line array (VLA) sensors that form part of a three-dimensional sensor array in the Arctic Ocean. Confidence limits estimated via Monte Carlo simulation indicate that transponders and sensors are localized to less than 1 m in three dimensions. The VLA sensor motion, monitored over a seven-week period, appears to be predominately driven by tidal currents and is consistent with historical current measurements for the region 相似文献
9.
Bok Kyoung Choi Bong -Chae Kim Byoung -Nam Kim Suk Wang Yoon 《Ocean Science Journal》2006,41(4):195-199
Comparative study was carried out for an acoustic iterative inverse method to estimate bubble size distributions in water.
Conventional bubble sizing methods consider only sound attenuation for sizing. Choi and Yoon [IEEE, 26(1), 125–130 (2001)]
reported an acoustic iterative inverse method, which extracts the sound speed component from the measured sound attenuation.
It can more accurately estimate the bubble size distributions in water than do the conventional methods. The estimation results
of acoustic iterative inverse method were compared with other experimental data. The experimental data show good agreement
with the estimation from the acoustic iterative inverse method. This iterative technique can be utilized for bubble sizing
in the ocean. 相似文献
10.
Marine risers are susceptible to sustained vortex-induced vibration (VIV) because of their slenderness and light damping. Commonly used tools for analyzing VIV and the associated fatigue damage are based on the finite element method and rely on simplifying assumptions on the riser's physical model, the flow conditions, and characteristics of the response. In order to assess the influence of VIV and to ensure the integrity of the riser, field monitoring campaigns are often undertaken wherein data loggers such as strain sensors and/or accelerometers are installed on such risers. Given the recorded riser's dynamic response, empirical techniques can be used in VIV-related fatigue estimation. These empirical techniques make direct use of the measurements and are intrinsically dependent on the actual current profiles. Damage estimation can be undertaken for the different current profiles encountered and can account explicitly even for complex riser response characteristics. With a significant amount of data, “short-term” fatigue damage probability distributions, conditional on current, can be established. If the relative frequency of different current types is known from a separate metocean study, the short-term fatigue damage distributions can be combined with the current distributions to yield an integrated “long-term” fatigue damage model, which then can be used to predict the long-term cumulative fatigue damage for the instrumented riser. Non-parametric statistical techniques (that do not assume a specific function for the underlying distribution as parametric techniques do) are employed to describe the short-term fatigue damage data. In this study, data from the Norwegian Deepwater Programme (NDP) model riser experiments are used to demonstrate the effectiveness of empirical procedures and non-parametric statistics applied to field measurements to predict long-term fatigue damage, life, and probability of fatigue failure. 相似文献
11.
The often poor quality of ocean bottom seismic data, particularly that observed on horizontal seismometers, is shown to be the result of instruments responding to motions in ways not intended. Instruments designed to obtain the particle motion of the ocean bottom are found to also respond to motions of the water. The shear discontinuity across the ocean floor boundary results in torques that cause package rotation, rather than rectilinear motion, in response to horizontal ground or water motion. The problems are exacerbated by bottom currents and soft sediments. The theory and data presented in this paper suggest that the only reliable way of obtaining high fidelity particle motion data from the ocean floor is to bury the sensors below the bottom in a package with density close to that of the sediment. Long period signals couple well to ocean bottom seismometers, but torques generated by bottom currents can cause noise at both long and short periods. The predicted effects are illustrated using parameters appropriate for the operational OBS developed for the U. S. Office of Naval Research. Examples of data from ocean bottom and buried sensors are also presented. 相似文献
12.
The flexible riser top connection is a critical region for lifetime assessment due to large tension/curvature variations and modeling uncertainties. The bend stiffener polyurethane mechanical response not only presents a nonlinear loading rate and temperature dependency but is also subjected to weather ageing during operation, which may affect its mechanical behavior over time. The top tension, employed for riser local cross-section stress calculation, is usually obtained from global dynamic analyses performed under selected environmental conditions, if direct measurement is not available. As a consequence, both the bend stiffener effect on the curvature distribution and the top tension time series present inherent uncertainties for riser lifetime (re)assessment. In the present work, a proposed monitoring approach composed by gyrometers installed along flexible riser/bend stiffener top connection system length combined with an inverse problem methodology is numerically investigated to estimate the following parameters: (i) polyurethane hyperelastic response and (ii) effective top tension. The top connection system is modeled using a large deflection beam bending model and the parameters are estimated using a damped least-square minimization approach with the Levenberg–Marquardt algorithm. For the preliminary feasibility investigation, the gyrometer experimental data is numerically estimated through Monte Carlo simulations. A case study is carried out to investigate the influence that the number of sensors, sensors arrangement, loading conditions and top connection model have on the inverse parameters estimation. The results indicate that the proposed monitoring approach and inverse parameter estimation methodology may effectively reduce flexible riser lifetime calculation uncertainties. 相似文献
13.
Wen-Hui Cheng 《Ocean Engineering》2006,33(10):1271-1282
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. 相似文献
14.
《Ocean Engineering》2007,34(14-15):1909-1917
Low frequent motions of vessel may cause motion sickness in rough seas. These undesirable effects induce fatigue of crews during the navigation. The motion sickness is always an important criterion for the high-speed craft design. Modern ferry designs have been marketed with a great emphasis on the seakeeping performance. This research has been carried out by investigating the results on the vertical motion sickness incidence (MSI) study for a 40 m wave-piecing catamaran at seas. The primary purpose of this research is to investigate the vertical motion sickness characteristics of a high-speed catamaran ferry. Two mathematical models, three-dimensional translating–pulsating source distribution technique and three-dimensional pulsating source distribution technique, are used for predicting the vertical acceleration responses of the wave-piecing catamaran in oblique waves. The comparison between numerical predictions and experimental data shows a good agreement except that around the pitch resonance region in FP vertical acceleration motions. Based on the experimental observation, the discrepancies may be caused by the nonlinear effects of centre bow during large pitch motions in waves. The comfort assessments are based on the ISO-2631/1997 standard with the hydrodynamic analysis for determining the acceleration levels in different locations on the vessel. The effects of seating location, wave heading and duration of motion exposure on seasickness are discussed. 相似文献
15.
To establish viable earthquake counterplans for ports in Korea, data regarding earthquake motion on the ground and in buildings must be collected using acceleration monitoring systems. Acceleration monitoring-based strategies for port facilities are useful not only for ensuring rapid responses during and after earthquakes but also for regional data collection to assist reliable seismic design. Acceleration monitoring systems were installed at coastal facility sites in target ports, including a soil site to represent the facility and a rock site as a reference. The systematic earthquake alert software was designed to help them in decision-making about a possible seismic hazard and its reporting. The earthquake alert system was composed of two sequential functional software systems sharing an acceleration monitoring database applied to the target ports. The earthquake response software system triggers an alarm based on the peak ground acceleration per second computed from the monitored data. Then, the earthquake hazard estimation software system evaluates possible earthquake-induced site-specific geotechnical hazards linked to the peak ground acceleration. The integrated system was successfully operated and was able to rapidly provide an emergency report containing event records and geotechnical earthquake hazards during the September 2016 Gyeongju earthquake, the largest recorded earthquake in Korea. 相似文献
16.
Geometric distortions in side-scan sonar images: a procedure fortheir estimation and correction 总被引：1，自引：0，他引：1
A procedure is introduced for the estimation and correction of geometric distortions frequently observed in side-scan sonar images as a result of motion instabilities of the sonar towfish. This procedure estimates geometric distortions from the image itself, without requiring navigational or altitude measurements. Estimates of the local degree of geometric distortion are obtained by cross-correlating segments of adjacent lines of the image. A mathematical model for the distortions is derived from the geometry of the problem and is applied to these estimates to reconstruct the sampling pattern on the seabed, under the assumption of a planar bottom. The estimated sampling pattern is then used for resampling the image to correct the geometric distortions. The model parameters may also be used for calculating approximate estimates of the attitude parameters of the towfish. A simulation is employed to evaluate the effectiveness of this technique and examples of its application to high-resolution side-scan sonar images are provided 相似文献
17.
Vilibic I. Dadic V. Ivankovic D. Beg Paklar G. Cupic S. 《Oceanic Engineering, IEEE Journal of》2007,32(2):428-435
This paper encompasses the analyses of sea level data measured at four tide gauges situated in the city of Split, Croatia. Two old long-term stations comprise float-type instruments in stilling wells, with analog recording on a chart, while two modern stations were installed in 1999 and 2000, calculating sea level height from the measured sea and air pressure. Although analog recording devices with a drum may suffer from inaccuracy in timing and drum rotation speed, clock errors, and vertical pencil position, the largest errors in the data came from the digitizing process, which is subjected to the individual work of a technician. Although, the data collected with pressure systems are supposed to be more homogeneous and accurate, after several years of work, the sensors usually have a drift in time. This problem turned out to be accompanied with lower quality sensors being part of wider automatic measuring systems, whereas the station which has been specially designed for sea level measurements showed no drifts in four years of operating. Therefore, one should be careful in choosing measuring equipment between various manufacturers. In addition, the equipment should be regularly checked since the malfunction in global positioning system (GPS) clock resulted in time drift of sea level data of more than an hour. 相似文献
18.
船只目标SAR、HFSWR和AIS多手段融合探测的点迹关联分析 总被引：3，自引：1，他引：2
A space-borne synthetic aperture radar （SAR）, a high frequency surface wave radar （HFSWR）, and a ship automatic identification system （AIS） are the main remote sensors for vessel monitoring in a wide range. These three sensors have their own advantages and weaknesses, and they can complement each other in some situations. So it would improve the capability of vessel target detection to use multiple sensors including SAR, HFSWR, and A/S to identify non-cooperative vessel targets from the fusion results. During the fusion process of multiple sensors＇ detection results, point association is one of the key steps, and it can affect the accuracy of the data fusion and the efficiency of a non-cooperative target＇s recognition. This study investigated the point association analyses of vessel target detection under different conditions： space- borne SAR paired with AIS, as well as HFSWR, paired with AIS, and the characteristics of the SAR and the HFSWR and their capability of vessel target detection. Then a point association method of multiple sensors was proposed. Finally, the thresholds selection of key parameters in the points association （including range threshold, radial velocity threshold, and azimuth threshold） were investigated, and their influences on final association results were analyzed. 相似文献
19.
基于AIS信息校准的双频地波雷达的船只融合跟踪 总被引：2，自引：0，他引：2
高频地波雷达（HFSWR）和自动船只确认系统（AIS）是船只跟踪的重要传感器。高频地波雷达可以用来跟踪探测区域的所有船只，而AIS只能用来确认合作船只的信息。由于海杂波的干扰，使用单频率地波雷达的船只跟踪会淹没在布拉格峰值的盲区里，改变探测频率是克服这一缺点的有效手段。在这种背景下，我们提出一种基于AIS校准的双频雷达融合探测算法。因为不同频率的地波雷达测量与AIS的测量值存在系统误差，所以AIS信息可以用来估计和校准地波雷达的每个频率的系统误差。首先，将合作目标的点迹测量与地波雷达的点迹测量通过JVC分配算法进行点迹关联。从合作船只的点迹关联结果中，双频雷达的系统误差可以估计和校准。其次，基于校准的双频雷达数据，使用融合JPDA-UKF算法进行船只跟踪。通过真实探测的数据的实验结果显示所提算法可以实时跟踪船只，相比单频率跟踪可以进一步提高跟踪能力和跟踪精度。 相似文献
20.
The Hawaii-2 Observatory 总被引：2，自引：0，他引：2
Petitt R.A. Jr. Harris D.W. Wooding B. Bailey J. Jolly J. Hobart E. Chave A.D. Duennebier F. Butler R. Bowen A. Yoerger D. 《Oceanic Engineering, IEEE Journal of》2002,27(2):245-253
A permanent deep ocean scientific research facility-the Hawaii-2 Observatory (H2O)-was installed on the retired HAW-2 commercial submarine telephone cable in September 1998. H2O consists of a seafloor submarine cable termination and junction box in 5000 m of water located halfway between Hawaii and California. The H2O infrastructure was installed from a large research vessel using the Jason ROV and standard over-the-side gear. The junction box provides two-way digital communication at variable data rates of up to 80 kbit/s using the RS-422 protocol and a total of 400 W of power for both junction box systems and user equipment. Instruments may be connected by an ROV to the junction box at 8 wet-mateable connectors. The H2O junction box is a "smart" design, which incorporates redundancy to protect against failure and allows full control of instrument functionality from shore. Initial instrumentation at the H2O site includes broad-band seismometer and hydrophone packages 相似文献