A cross-correlation detection method to process backscatter signals of multi-laser beams measuring （MLBM） is presented, which can be firstly filtered by the digital filter composed of average median filter and finit...A cross-correlation detection method to process backscatter signals of multi-laser beams measuring （MLBM） is presented, which can be firstly filtered by the digital filter composed of average median filter and finite impulse response （FIR） digital filter. The processing of backscatter signals using single-pulse and three-pulse cross-correlation detection methods is depicted in detail. From calculation results, the multi-pulse cross-correlation detection could effectively improve signal-to-noise ratio （SNR）. Finally, both wind velocity and direction are determined by the peak-delay method based on the correlation function which shows high measuring precision and high SNR of the MLBM system with the assistance of the digital cross- correlation detection.展开更多
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 underwat...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.展开更多
Beamforming is one of the most important part of signal processing in sonar system.Traditionally, in the analogue system the bearing direction is steered by rotating some kind of time-delay compensator, which is usual...Beamforming is one of the most important part of signal processing in sonar system.Traditionally, in the analogue system the bearing direction is steered by rotating some kind of time-delay compensator, which is usually made by machanic-clectronic components. But,there exists a fixed bias error in target tracking due to the application of discrete tapped delay line. With the development of digital sonar the multi-beamforming technique is extensively used in various sonar systems. In these systems each beam has a fixed bearing direction. The precise DOA (Direction Of Arrival) estimation of the target becomes more important in sonar design. General speaking, if the sampling frequency is high enough, it is possible to get arbitrary number of beams, which steer in any designated direction. But a hardware tradeoff must be taken account for a good designer. In order to obtain higher target spatial resolution and reduce the hardware cost, it is necessary to make some kind of interpolation algorithm in post beamforming. It is proved that in the most interested situation the behavior of directivity function in the neighborhood of main lobe depends on the sinc function and zero order Bessel function. The multi-beam data is actually the spatial sampling to these function. Based on the principle of parabolic interpolation, a simple but high accuracy beam interpolation technique is presented in this paper. The theoretical basis of three-point and five-point interpolation algorithm is described. As an example, the line array and circle array of hydrophones are illustrated to explain this algorithm. The results of system simulation show that the method proposed in this paper has good agreement with the theory. It can be used to improve the behavior of the directivity function and enhance the multi-target resolving ability of digital sonar system. It is also possible to use this technique to implement ATT (Automatic TargetTracking) in real time.展开更多
基金supported by National Natural Science Foundation of China under Grant No. 60425101-1Foundation for Innovative Research Groups of NSFC under Grant No. 60721001
文摘A cross-correlation detection method to process backscatter signals of multi-laser beams measuring （MLBM） is presented, which can be firstly filtered by the digital filter composed of average median filter and finite impulse response （FIR） digital filter. The processing of backscatter signals using single-pulse and three-pulse cross-correlation detection methods is depicted in detail. From calculation results, the multi-pulse cross-correlation detection could effectively improve signal-to-noise ratio （SNR）. Finally, both wind velocity and direction are determined by the peak-delay method based on the correlation function which shows high measuring precision and high SNR of the MLBM system with the assistance of the digital cross- correlation detection.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51179035 and 51279221)the Natural Science Foundation of Heilongjiang Province(Grant No.E201121)
文摘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.
文摘Beamforming is one of the most important part of signal processing in sonar system.Traditionally, in the analogue system the bearing direction is steered by rotating some kind of time-delay compensator, which is usually made by machanic-clectronic components. But,there exists a fixed bias error in target tracking due to the application of discrete tapped delay line. With the development of digital sonar the multi-beamforming technique is extensively used in various sonar systems. In these systems each beam has a fixed bearing direction. The precise DOA (Direction Of Arrival) estimation of the target becomes more important in sonar design. General speaking, if the sampling frequency is high enough, it is possible to get arbitrary number of beams, which steer in any designated direction. But a hardware tradeoff must be taken account for a good designer. In order to obtain higher target spatial resolution and reduce the hardware cost, it is necessary to make some kind of interpolation algorithm in post beamforming. It is proved that in the most interested situation the behavior of directivity function in the neighborhood of main lobe depends on the sinc function and zero order Bessel function. The multi-beam data is actually the spatial sampling to these function. Based on the principle of parabolic interpolation, a simple but high accuracy beam interpolation technique is presented in this paper. The theoretical basis of three-point and five-point interpolation algorithm is described. As an example, the line array and circle array of hydrophones are illustrated to explain this algorithm. The results of system simulation show that the method proposed in this paper has good agreement with the theory. It can be used to improve the behavior of the directivity function and enhance the multi-target resolving ability of digital sonar system. It is also possible to use this technique to implement ATT (Automatic TargetTracking) in real time.
