Key Technologies Research On Independent Alignment Of Strap-down Inertial Navigation Syetem

Strap-down Inertial Navigation System(SINS), which is an integration of goodreliability,maintainability,providing more navigation information,and lowmanufacturing costs,is a new research and development trend of inertial navigationfield.Initial alignment is required before the Inertial Navigation System(INS) startsthe navigation.The independent alignment method of initial alignment which isindependent of external auxiliary equipments,gradually becomes outstanding for itsfine autonomy,strong concealment and low mechanical complexity and etc. Basedon the basic principle of the SINS, this paper proposed different autonomousalignment methods according to different stages of independent alignment under thecondition of static base, with simulations implemented,which verify their scope ofapplication, pros and cons.Independent alignment of SINS aims at building the mathematical platformand determining the carrier’s initial information.It’s inevitable that a variety oferrors will be introduced during alignment process,which brings unknown affectionto aligning accuracy and time.So this paper made a whole-system analysis on termsof SINS errors,with error equation of the system established.The precision ofnavigation calculating,which is the key step in the initial alignment,directly affectsalignment accuracy.Thus the navigation calculation was simulated in the article.Generally,coarse and fine aligning are two stages of independentalignment.During the coarse aligning stage,conventional method has loweralignment accuracy. So this paper presents an improved analytical method forcoarse alignment, with simulations given to test its rationality and effectiveness.Onprecision alignment stage, suppose that the misalignment after coarse aligning issmall, velocity error is not a good observables.Thus this paper proposes that gyro’sangular velocity error is measured as an extended volume.Under conditions of thestate equation unchanged,a measurement equation is established,with simulationsdone.When the misalignment after coarse aligning is large,or when coarse aligningis not convenient or not necessary, precise aligning should be considered. Focusingon the condition of large azimuth misalignment angle, this paper determined anonlinear independent alignment method. And this paper researched on KF,EKF and UKF filtering algorithm implementation process,with state and measurementequation deduced. Based on this, comparison of the three filtering algorithm isgiven by simulation.Results show that on condition of large azimuth misalignmentangle,KF is no longer applicable,UKF is better than EKF.At last,the core idea of HLA and its main components are introduced.And themain interface functions and debugging process of CEE simulation platform basedon HLA are studied while summarizing the relationship between alignment moduleand others.Based on that,the independent alignment is performed on the CEEsimulation platform, which meets the project indicators and lays the foundation forrealizing the missile simulation system.