A Self-Alignment Algorithm for SINS Based on Gravitational Apparent Motion and Sensor Data Denoising.

Yiting Liu,Xixiang Liu,Yiqing Yao,Liang Wu,Xiaosu Xu,Jin Sun

doi:10.3390/s150509827

Abstract

Initial alignment is always a key topic and difficult to achieve in an inertial navigation system (INS). In this paper a novel self-initial alignment algorithm is proposed using gravitational apparent motion vectors at three different moments and vector-operation. Simulation and analysis showed that this method easily suffers from the random noise contained in accelerometer measurements which are used to construct apparent motion directly. Aiming to resolve this problem, an online sensor data denoising method based on a Kalman filter is proposed and a novel reconstruction method for apparent motion is designed to avoid the collinearity among vectors participating in the alignment solution. Simulation, turntable tests and vehicle tests indicate that the proposed alignment algorithm can fulfill initial alignment of strapdown INS (SINS) under both static and swinging conditions. The accuracy can either reach or approach the theoretical values determined by sensor precision under static or swinging conditions.

Highlights

Initial alignment is always a precondition for an Inertial Navigation System (INS) to navigate [1,2].For INS, initial alignment is the acquisition of the initial velocity, position and attitude
The simulation time period is 600 s and the alignment errors are shown in Figure 5 where only constant sensor errors in InertialMeasurement Unit (IMU) can be seen, when the self-alignment for strapdown INS (SINS) based on three vectors of gravitational apparent motion in inertial frame can quickly complete the strapdown inertial navigation initial alignment
The self-alignment for SINS based on three different vectors of gravitational apparent motion in inertial frame is heavily affected by the random sensor errors

Summary

Introduction

Initial alignment is always a precondition for an Inertial Navigation System (INS) to navigate [1,2]. For INS, initial alignment is the acquisition of the initial velocity, position and attitude. Positioning System (GPS), initial alignment mainly refers to the acquisition of initial attitude. INS (SINS) uses a mathematical platform as a navigation platform, where the initial alignment obtains the matrix between the body frame and navigation frame [3,4,5]. The technical manuals of the Octans system developed by the IxBlue Company (Marly le Roi, France) claim that the Octans can complete initial alignment under any swinging conditions within 5 min by observing the drift of gravity in an inertial frame (gravitational apparent motion) [6,7]. Inspired by the alignment idea of tracing apparent motion, many realization methods have been proposed since 2000, which can be divided into two types, namely attitude determination based on dual vectors and vector-operational [8,9,10,11,12,13,14,15,16,17,18,19,20]

Methods

Results

Conclusion