Analytic Alignment Methods For SINS Based On Vector-Calculation In Inertial Frame

Initial alignment is a classic and critical topic of strapdown inertial navigation system(SINS).In this dissertation,the analytical inertial alignment method based on vector computation is studied under different conditions.This paper mainly includes four parts as follows:Firstly,the basic knowledge of SINS is introduced,and the differential equations of attitude updating algorithm is analyzed in detail.Conventional dual-vector attitude determination method is summarized,and its application conditions are pointed out by simulation analysis,which derives initial alignment problem based on inertial frame under swinging condition.Secondly,in order to solve the initial alignment problem under swinging condition,the chain rule is used to split the attitude matri Cbn into Ce(t)n(t)?Ce0e(t)?Cib0e0 and Cb(t)ib0,then it becomes the problem of finding solutions for Cib0e0,the dual-vector attitude determination method is used to solve this.The parameter identification and reconstruction method of recursive least square method is briefly introduced to estimate the effects of accelerometer measurement noise on alignment accuracy..Furthermore,the method of parameter identification and reconstruction based on Newton-Lagrange iteration method is introduced.However,the method mentioned above need the accurate latitude information during the alignment.In this scenario,the problem of initial alignment is to find the solution for Cib0n and the three-vector attitude determination method is used to solve this.Simulation results show the effectiveness of all the proposed algorithm.Thirdly,for the initial alignment problem under moving condition,external velocity and position reference information is introduced.The initial alignment problem is simplified to the problem of Wahba attitude based on multi vector,and attitude determination is completed by Q-method;The mechanism that the eigenvectors corresponding to the minimum eigenvalue of the matrix is the optimal estimation for the initial quaternion is analyzed in detail.The simulation results show the effectiveness of the proposed algorithm.At last,to estimate the lever arm length and instrument errors in the process of initial alignment,the instrument error and lever model under moving condition is established.Through transposition/integration/discretization on the basic equations of SINS,the problem of instrument error and lever parameters can be solved by the calculation of the extremum of multivariate function using the Newton-Lagrange iteration algorithm.Under different motion states and simulation conditions,the algorithm is verified by simulation.