Research On Key Technology For Fast Initial Alignment Of Vehicle-mounted Fiber Strapdown Inertial Navigation System

The focus of INS research is to improve the performance of initial alignment.Especially in the military field,navigation equipment with high accuracy,strong anti-jamming,and quick response is an inevitable requirement for modern high-tech warfare.The rapidity,strong antijamming capability and high accuracy of navigation equipment are inevitable in modern hightech warfare.The goal of this research is to shorten the initial alignment time of the vehiclemounted strapdown inertial navigation system.The performance index of the initial alignment to be finally achieved is: when the alignment accuracy is better than 0.06°/cos?,the alignment time is less than 5min.The main contents and contributions of this research include the following aspects:1.The equations,attitude update algorithms and error equations of the strapdown inertial navigation system are derived.2.The hardware circuit of the orientation component is designed,including the design of the navigation computer circuit and the design of the core processing circuit.3.The interference signal in the case of vehicle shaking base is analyzed.And the necessity of alignment pre-filtering in the case of vehicle shaking base is explained.Then the least squares fitting,FIR,IIR filtering and wavelet alignment pre-filtering methods are theoretically analyzed.By comparison,EMD filtering is selected for pre-filtering method research.In order to solve the problem of EMD end effect and modal aliasing,the end effect is suppressed based on the correlation of extreme points,and the modal aliasing is suppressed based on singular value decomposition,and the EMD filtering method is improved.An on-vehicle alignment experiment was carried out,the output data of the inertial instrument under the on-board base was collected,and it was filtered,and the effectiveness of the improved pre-filtering scheme was verified.The designed EMD pre-filtering scheme is conducive to the subsequent rapidity of this topic Alignment method.4.The alignment errors of the three coarse alignment methods are deduced and analyzed.Finally,for the actual application of the swaying base-vehicle in this paper,the coarse alignment of the inertial fixed frame is selected as the coarse alignment scheme.5.Considering the rapid alignment in the case of large azimuth misalignment angle,a nonlinear error equation is established.The convergence speed and calculation amount of several nonlinear filter fine alignment methods were analyzed and compared,and UKF filter fine alignment is chosen as the optimal method of nonlinear fast alignment.Considering that the UKF algorithm has the disadvantage of large amount of calculation,it needs to be improved.The conditional linearity of the nonlinear model is used to reduce the Sigma sample points in the traceless transformation process,thereby reducing its calculation amount and shortening the alignment time.Simulation experiments were carried out.Finally,a quick alignment solution applied to the vehicle is given.6.An experiment is designed to verify that the vehicle-mounted quick alignment scheme meets the accuracy index requirements.Firstly,the static base alignment test is designed: horizontal base alignment accuracy test,tilt base alignment accuracy test,high and low temperature experiment,and the alignment performance of the vehicle-mounted rapid alignment algorithm is tested under the static base;then on-vehicle alignment experiment is designed: idle-speed alignment experiments,navigation experiments.And the experimental results met the expected goals.