Research On Underwater Multi-Target Cooperative Localization Positioning Algorithm

In recent years,with the development and use of the ocean,autonomous underwater vehicles play an important role in the fields of deep sea resource survey,hydrological environment monitoring,deep water mine clearance and so on.It is an important guarantee for its successful completion and return.When it is necessary to carry out exploration or other operations in the unknown environment for a long time and a long distance,the inertial navigation error will gradually increase with the increase of working time because of its own characteristic positioning error.However,the accuracy of positioning by Doppler velocimeter will gradually decrease with the increase of the voyage distance.It is too expensive to use the mother ship to follow or set up the beacon in advance and calibrate it.And it is easy to be affected by the weather or water environment,resulting in poor positioning effect and so on,which has great limitations.The cooperative localization algorithm is developed to solve these problems.It is defined as the method of position correction and location by using other AUV in the team to deal with the location AUV by transmitting information between each AUV.Because of its necessity and importance,cooperative positioning has gradually become the mainstream research direction and research hotspot of underwater AUV positioning.In this paper,the existing collaborative localization algorithms and experimental cases are analyzed and studied.The existing methods have the following problems: 1.unable to locate multiple AUV at the same time;2.Too much information is transmitted during the positioning process;3.too much information transferred in the localization process,and too much computation of some algorithms when the number of AUV increases.For the master-slave AUV structure,in order to solve the above problems,this paper uses a co-localization algorithm based on Indirect Adjustment and Helmert Variance estimation.The distance information between any two AUV and the velocity information of all AUV itself are used as observations,and the position information of AUV itself with errors is added to the adjustment equation,and the observation is corrected by co-localization algorithm.Allows all AUV in the team to modify their position based on sensors such as distance information during a co-location cycle and to obtain all other AUV position information to adjust their course and formation,And make the position accuracy of AUV in the team reach the same order of magnitude.The effects of ranging error,velocity error and different formation on the positioning accuracy are analyzed one by one.The simulation results show that the main AUV speed error has the greatest influence on the positioning accuracy of the team.When the error is 0.01 m/s,the average relative position error of the team AUV is 150 m,the ranging error and the slave AUV velocity error have little effect on the positioning accuracy,and when the AUV speed error is 0.1m/s,The average relative position error of the team AUV is about 3 m,When the ranging error is 0.3 m and the accuracy is 0.5 m,the average relative positioning error of the team AUV after sailing 50 min is about 4 m.Therefore,in the actual operation,under the premise of reducing the cost of AUV and decreasing the positioning accuracy,we should focus on improving the accuracy of the main AUV speed sensor,and the requirements of the AUV speed sensor and ranging can be reduced relatively.Finally,the experiment data of Songhua Lake are processed,the main AUV is simulated with the water surface carrier,and the experiment is carried out on the lake with four beacons instead of AUV,which verifies the feasibility of the co-location algorithm in practice.The experimental data show that,in the actual scene,the position information of the main AUV is replaced by the GPS information fixed on the water surface carrier with a period of 2s.The accuracy of the information is in the centimeter level,and the position marked by the beacon is taken as the true value.The average positioning errors of the four AUV were 0.503 m,0.543 m,0.571 m and 0.486 mrespectively,and the positioning errors of the four AUV were all less than 1m,which accounted for more than 90% of the total period.The co-location algorithm used in this paper has been verified by simulation and experimental data processing,which can meet the requirements of co-localization of multiple AUV and reducing the amount of information transfer and computation between AUV in practice.When the position information of the main AUV and the velocity accuracy are high enough,on the basis of obtaining the accurate equivalent sound velocity,the real-time cooperative positioning of the slave AUV can be carried out.