Research On Key Techniques Of Integrated LBL/USBL Accurate Positioning With High Frame Rate For Underwater Targets

In order to locate underwater moving targets with high-speed accurately and reliably,considering the development trend and actual working environment of underwater acoustic localization system,a measurement platform of integrated long baseline/ultra-short baseline(LBL/USBL)system high frame rate is built in the thesis.Main topics of this thesis are phase unwrapping techniques based on multi-subarray fusion,range ambiguity resolution method of high frame rate synchronous positioning system and multi-parameter fusion based anti-outlier accurate positioning technique in integrated LBL/USBL system.The main research contents are as follows:Aiming at the contradiction between the long-range high-precision requirement of USBL positioning and the phase wrapping problem,two techniques of phase unwrapping based on multi-subarray fusion are proposed.Firstly,a multi-element non-uniform array is constructed and the phase unwrapping problem is transformed into the classification recognition problem of the longest baseline ambiguity number.Then a phase unwrapping technique based on multiple classifier fusion is proposed.Secondly,to increase the tolerance of observational errors,the ambiguity number of the short baseline is estimated by the longest baseline,and a multiple composite hypothesis testing model is constructed.Then a phase unwrapping technique based on the generalized maximum likelihood criterion is proposed.The unambiguous observational conditions are deduced,and the resolution performance of the proposed method is analyzed based on the theoretical evaluation of the nonuniform linear array layout.The results of simulation and lake tests show that the two proposed phase unwrapping methods do not require an inter-sensor spacing less than half the wavelength,and have high tolerance to the phase-difference measurement error.Eventually,the phase wrapping problem can be effectively solved,and thus the long-range positioning capability of USBL system is improved.Aiming at the range ambiguity problem in synchronous underwater acoustic positioning systems with high frame rate,a range ambiguity resolution method based on time of arrival / direction of arrival(TOA/DOA)fusion and differential evolution(DE)algorithm is proposed.Under the maximum likelihood criterion,the optimization model with TOA/DOA fusion is established,which is solved by DE algorithm.The target region is effectively delimited utilizing the unambiguous feature of DOA information,which reduces the risk that the DE algorithm may fall into local minimums.Then the unambiguous positioning of the moving target in a large area is realized.In underwater acoustic multipath channel,a high-frame-rate positioning system faces the problem of range ambiguity and inter-periodic interference from reflecting signals.Aiming at this problem,a range ambiguity resolution method based on the comprehensive support degree is proposed.The time delay and phase difference of pulses received by the integrated baseline system are used to preliminarily estimate the target alternative positions.Then,the majority consistency of the target alternative positions is measured by the comprehensive support degree so as to estimate the ambiguity number corresponding to each pulse signal.The pulse travels in the direct path is selected by the expert system of multipath channel recognition.Finally,the effective discrimination of the ambiguity period number of the direct sound pulse is achieved under the complicated multipath channel.The simulations and lake trial results verify that the two proposed range ambiguity resolution methods do not need the prior information of the initial position of the target and can realize the ambiguous positioning of the moving target in a wide range of observation area.The integrated LL/USBL underwater positioning technique with high reliability and precision is studied.An accurate integrated baseline positioning method based on TOA and phase difference parameter fusion is proposed.Considering the statistical characteristics of the measured TOA and phase difference,a multi-parameter optimization positioning model under the maximum likelihood criterion is constructed,and the complementary advantage of the heterogeneous observation information is achieved,which guarantees the positioning accuracy of the entire measurement area.Complicated underwater environment puts forward high requirements on the fault-tolerant and reliability of underwater acoustic localization systems.In this regard,an anti-outlier localization method based on k-means clustering and decision fusion is proposed.Firstly,the target position is preliminarily estimated by the multi-parameter redundant information measured by the integrated baseline system.Then,the clustering degree of the preliminary measurements is analyzed by k-means clustering.According to the incompatibility between the outliers and the normal parameters,the outliers are identified by the decision fusion method.Furthermore,the impact of outliers on the positioning results is eliminated.Simulation analysis shows that the proposed anti-outlier positioning method fully incorporates the multi-parameter observation information,and the tolerance of outliers and positioning accuracy are better than the existing anti-outlier positioning methods based on time-delay parameter.The results of the lake test further verify the effectiveness and practicability of the method.