Research On Underwater Passive Detecting And Locating Technologies Based On Acoustic Vector Field

The restrictive effect of complex environment on sonar performance has been alwaysconsidered as one of the most important challenges in underwater acoustic physics filed andunderwater acoustic engineering filed. With the development of acoustic stealth technologyand long-distance countermeasure weapons, passive sonar meets a new challenge of the lowsignal-to-noise ratio detection. Thus, it is imperative to develop newly technology for thelong-distance passive detection in complex ocean environment by utilizing the characteristicsof target’s radiation acoustic field. On the other hand, the passive tracking of underwatermoving target is an important guarantee for the development of quiet submarine’scountermeasure weapons and other underwater vehicles. Under such circumstance, thetheoretical, experimental and applied research on two aspects of the most challenging subjectsin underwater passive detection and positioning technology were studied in this thesis,including the physical basis of passive detection and localization towards the mid-distance orlong-distance quiet targets and the key technologies of high-accuracy tracking and positioningtowards the underwater moving target. The key contributions are:1、Research on the interference structure of shallow water vector acoustic fieldThe normal mode expression of the shallow water vector acoustic field was deduced, andthe energy relations and energy characteristics of vector field was analyzed. The interferencestructural properties of vector acoustic field were researched through simulation. Based on thedefinition of waveguide invariant, the interference structure of vector sound field wasdescribed in waveguide invariant, whose characteristics was studied through theoreticalanalysis and numerical computation, and the verification by sea trials was commenced finally.The measurement fits in with the theoretical and simulation results very well.2、Space-time processing and applied research on interference structure of the shallowwater vector acoustic fieldMathematical expression of the conventional beam-forming output of vector line array inwaveguide conditions was deduced, and the impact mechanism of time-space samplingcoherent process on vector field interference structure was analyzed. The characteristics ofinterference structure in beam field were researched through simulation. It is verified that thenatural invariance of stripe slope remain the same, although several aspects of beam domainoutput interference fringe,including intensity, distribution and so on, would change with themodulation of beam map. The mapping method of interference spectrum and the characteristics of the ridge in mapping space were discussed, and the implement of targetdetection and warning, which was based on the interference structure of vector acoustic field,was proposed. The performance of this implement was analyzed through simulation andchecked through the data measured in sea trial. The research results show that this implementcan detect mobile and immobile targets effectively and can indicate the target’s motion state.3、Research on the key technologies of distributed vector array passive positioningThe impact of motion interference on Distributed Positioning System was analyzed, anda new method of direction estimation based on single vector hydrophone in motioninterference background was put forward, named oriented intensity implement. Theperformance of this implement was analyzed through simulation, and sea trials verify andeffects assessments were done. The statistical properties of pseudo sequence in the directionestimator based on single vector hydrophone was studied, and a multi-station cooperatingmethod based on pseudo sequence analysis in passive locating and tracking distributedsystems was proposed, whose application on track establishment and multi-stationcooperation was discussed.The method can reduce lots of false alarms effectively during theprocess of setting up initial path, and can fuse multi-station information very well. Combinedwith oriented intensity implement, it can also improve the anti-interference capability ofdistributed passive positioning system. The method has been put into practical application.4、Research on the estimation method of effective sound velocity in shallow water and itsapplicationA new estimation method of effective sound velocity in shallow water based onEigen-rays pseudo searching was put forward, and the physical images of the spacedistribution of effective velocity in three kinds of shallow water channel were acquired.According to the concept of effective velocity gradient, the space variable characteristics wereanalyzed. The experiment about effective sound velocity measurement was carried out inshallow water, and the application of effective sound velocity and its estimation method wasdiscussed, such as the forecast of system range, the planning of array position in long baselineacoustic positioning system, the establishment of high-accuracy positioning model, and so on.The application results showed its effectiveness.The forward two aspects of these research results above not only have great significancein improving the robustness of the detection and the recognition toward the quiet targets, butalso have many practical applications in remote passive ranging, underwater environmentalmonitoring and underwater acoustic communication. The backward two aspects can enhancethe performance and capacity of underwater maneuvering target high-accuracy passive location and is useful in underwater acoustic ranging, distributed active positioning systemand channel matching.