Research On Three-dimensional Laser Doppler Velocimeter And Its Application In Inertial Navigation

At present,the inertial navigation system(INS)has been widely used in the field of navigation,but it has the following two main shortcomings:(1)The horizontal positioning error of INS accumulates with time;(2)The altitude channel of INS is not damped,so the altitude is completely divergent.To make up for the shortcomings of INS,the integrated navigation has become a developing trend of inertial navigation technology.Our team has been committed to the development of vehicle-mounted laser Doppler velocimeter(LDV),in order to achieve high-accuracy horizontal and altitude positioning with the integrated navigation of INS.This paper takes three-dimensional(3D)laser Doppler velocimetry as the research objective,aiming to further expand the application range of LDV and improve the integrated navigation accuracy.The research work includes the following four aspects:1.Structure design of 3D LDV and performance test of single probe.From the application characteristics and symmetrical redundancy of LDV,a 3D LDV with four-beam based on the reference-beam structure is designed.The values of the beam inclinations and included angles of the 3D LDV with four-beam are selected from the aspects of normalized scattered light power,total detection sensitivity and unidirectional detection sensitivity.According to the design,the manufacture of the 3D velocimeter is completed.A series of experiments are carried out to evaluate the performance of each single probe and the velocity measurement accuracy,the length measurement accuracy,the measurement linearity,the depth of field and the lower velocity limit of each probe are measured.2.The random error and filtering algorithm of LDV.The random error characteristics of LDV are studied.To reduce the random error,the traditional time series method is improved,and the metabolic time series model is put forward.On this basis,three filtering methods including the metabolic double time series model,the metabolic grey-time series model and the metabolic time series-grey model,which can reduce the static and dynamic random error of LDV in real time,are proposed,and the filtering effects of these three models are analyzed and compared in detail.3.Calibration method of LDV in integrated navigation.With the 3D LDV with four-beam,the calibration problems of five kinds of LDVs are systematically studied and a secondary filtering calibration method is proposed.The velocity error models of the one-dimensional(1D)LDV with single-beam,1D LDV based on Janus Configuration,two-dimensional(2D)LDV,3D LDV with three-beam and 3D LDV with four-beam are derived.The calculation processes of the secondary filtering calibration method in the parameter calibration of the five kinds of LDVs are given.The effects of vehicle jolts and load variations on the calibration parameters of the 1D LDV with single-beam,1D LDV based on Janus configuration,2D LDV are described.The observability of the relative error parameters of these two kinds of 3D LDVs is analyzed,and the condition that all the relative error parameters can be observed is obtained:loading different direction velocities for the integrated system.The applicability of the secondary filtering calibration method is verified by simulation experiments.4.Integrated navigation experiments of LDV.A series of vehicle integrated navigation experiments for the five kinds of LDV are carried out.The advantages and disadvantages of the 1D LDV with single-beam,1D LDV based on Janus configuration,2D LDV are further verified and analyzed.Through the rotation of the integrated system of 3D LDV relative to the vehicle,the purpose of loading different direction velocities for the system is realized,and all the relative calibrated parameters of 3D LDV converge.Eight groups of the vehicle integrated navigation experiments of 2D LDV,3D LDV with three-beam and 3D LDV with four-beam are presented,and the horizontal positioning accuracies are between D0.063‰ and D0.113‰ and the altitude positioning accuracies are between D0.006‰ and D0.025‰,where D is the total travel.The universality of the calibrated parameters is verified by cross navigation.Combined with the practical application of the integrated navigation system,a redundant integrated navigation scheme of the 3D LDV with four-beam is presented to improve the reliability of the integrated navigation system and ensure that the integrated navigation system can work normally when one or several probes of the LDV are unable to measure the velocity normally,and the correctness of the scheme is verified.