Research On Underwater Sound Speed Correction Algorithm And Precision Positioning Method

The ocean is a huge treasure house of resources,but it has not been fully exploited.With the gradual depletion of land resources,Marine resources become increasingly important.China put forward the goal of building a maritime power in the report of the 18 th national congress of the communist party of China.However,the existing national space datum and gravity datum have not effectively covered the ocean,and marine geodesy datum and marine navigation technology have lagged behind the new situation of national social and economic development and national defense strategic needs.According to the urgent need of people for underwater positioning technology,this paper conducts researches on some key technical issues in underwater positioning technology under the support of national key research and development program "Marine geodetic datum and new marine navigation technology".It is summarized as follows:1.This paper summarizes the research status of underwater positioning technology,sound speed correction model and underwater positioning model algorithm at home and abroad.,After that,it introduces several common underwater positioning systems,and analyzes the advantages and disadvantages of various systems as well as their applicable conditions.The various error sources in underwater acoustic positioning and the formation principle of the error are described in detail,which lays a foundation for the reduction and even elimination of the acoustic error in the future.2.The most important error source in underwater navigation is sound velocity error,which needs to be corrected in positioning.Therefore,the sound velocity correction algorithm in underwater acoustic positioning is studied.Firstly,several common sound speed correction methods are introduced,and the sound velocity correction algorithm is improved based on above methosds.Secondly,an adaptive stratification method is used to extract the sound velocity profile data reasonably to ensure the sound velocity layer with a large amount of information.Then,an improved sound ray tracking algorithm is proposed.This method uses the sound ray propagation principle along the arc,calculates the sound velocity propagation time integrally,and solves the target position through an iterative method.Finally,the simulation data are used to verify the algorithm,and the following conclusions are obtained: compared with the traditional layered equal gradient sound ray correction algorithm,the improved adaptive hierarchical sound ray tracking algorithm significantly improves the positioning efficiency under the condition of ensuring the positioning accuracy.3.Aiming at the problem of systematic error control in underwater positioning,the semi-parameter model estimation method is applied to underwater acoustic positioning data processing.Firstly,the method of semi-parametric compensation least-squares estimation is described.Secondly,the selection method of smoothing factor and normal matrix in semi-parametric model is introduced.Finally,the effectiveness of the semi-parametric model in underwater location is verified by simulation and measured data.Results show that the semi-parametric model adds a systematic error parameter in every epoch.Then the systematic error can be calculated through compensated least squares and regularization algorithm.The method solved the problem that too many parameters cause the normal equation to be morbid.At the same time,it can weak the influence of systematic error,and improve the accuracy of underwater acoustic positioning.4.It is inevitable that there are gross errors in underwater acoustic positioning,and the traditional least square method cannot achieve robust estimation.To solve this problem,robust estimation is applied to underwater acoustic positioning.Firstly,some common weight functions are introduced,and it is found that IGGIII has good robusteffect under the condition of different gross error.Then the IGGIII is combined with buoy differential positioning and semi-parametric model to get the method of buoy differential positioning model and semi-parametric positioning model based on IGGIII robust estimation.Simulation examples show that the buoy differential positioning model based on IGGIII can weak the influence of systematic error by differential mode.At the same time,it also has good tolerance,effective controls the effects of gross errors,and significantly improves the positioning accuracy.The semi-parametric model based on IGGIII can suppress the effects of both systematic error and gross error at the same time.Compared with the classical semi-parametric compensated least squares estimation method,the new method has broader applicability.