Study On Optimization-based Alignment For Strapdown Inertial Navigation Systems On Moving Base

With the development of national economics and defense, the strapdown inertialnavigation system (SINS) has been widely used in many military and civil fields.Alignment is one of the most important technologies for SINS and vital to theperformance of SINS, which receive much attentions from navigation. It is believed thatthe static alignment has been well settled. In contrast, the alignment for SINS onmoving base is one of the research hotspots, but most of the studies focus on improvingperformance of the fine alignment. The coarse alignment is lack of serious attentions sofar unfortunately.The thesis pays close attention to the problems of alignment for SINS on movingbase. Starting from the basic alignment theory, the thesis analyzes and compares themoving-base alignment algorithms. Finally, the thesis stresses the analysis andexperiments on the in-motion alignment. The primary works are as follows:1. The traditional SINS alignment algorithms on moving base are studied in detailstarting from the fundamental theory of alignment. The problem in SINS alignmentalgorithms is consequently deduced.2. The thesis investigates the inertial-frame alignment algorithm andoptimization-based alignment from their principle respectively. It validates performanceof two algorithms using both the static data derived from simulation and the swayingdata collected from the swaying table. The results show that the inertial-framealignment can basically meet the need of coarse alignment and the integral strategy canwell restrain the disturbing velocity. At the benefit of fully using the information in thedata, the optimal-based alignment algorithm completely satisfies the requirement ofcoarse alignment and is generally superior to the inertial-frame alignment algorithm.3. Based on the optimization-based idea, the thesis studies two methods forimplementing optimization-based in-motion alignment: integral method and differentialmethod. Two experiments are used, namely, the one with the high-accuracy SINS andthe other with the Micro-electro-mechanical (MEMS) SINS, to validate the performanceof the optimization-based alignment in the in-motion case. The results show that withthe velocity/position provided by Global Positioning System (GPS), theoptimization-based in-motion alignment algorithm can accomplish the coarse alignmentin100s in the high-accuracy SINS experiment. In addition, the integral method is morestable than the differential method. In the MEMS-used experiment, if a proper mobilepath is executed for the vehicle, the optimization-based alignment can reduce the yawerror of to about5degree by the differential method. But the integral method is notsuitable for the low-accuracy MEMS systems.The study of thesis shows that the optimization-based alignment algorithm can meet the requirement of alignment on moving base and thus has a wide applicationprospect.