INS Fine Alignment With Low-Cost Gyroscopes: Adaptive Filters for Different Measurement Types

Itzik Klein,Yaakov Bar-Shalom

doi:10.1109/access.2021.3079381

Abstract

Inertial navigation system stationary fine alignment process is a critical step in reducing the initial errors of the attitude and sensor biases. While many studies had been made for tactical grade systems, less attention was given to low-cost sensors, which are a major player in today’s inertial sensors market. To fill this gap, a measurement strategy combining different INS aiding types is proposed, analyzed and compared using numerical simulations and field experiments. Additionally, an analytical linear observability analysis is made to support the numerical comparisons. Further, five types of adaptive Kalman filters with the proposed measurement strategy are compared to find the appropriate one to improve the alignment performance. The proposed measurement strategy can be used in other applications of stationary conditions such as land vehicles, robots or shoe-mounted inertial navigation systems.

Highlights

Inertial Navigation Systems (INS) are commonly used in many types of platforms such as autonomous vehicles, quadrotors, ships, airplanes and more
The initial attitude can be provided by external sensors or by using the INS inertial sensors in a process known as analytic coarse alignment
There, when the platform is in stationary conditions, the accelerometers and gyroscopes outputs are compared to the expected values of the gravity and Earth turn rate vectors, to calculate the initial attitude vector

Summary

INTRODUCTION

Inertial Navigation Systems (INS) are commonly used in many types of platforms such as autonomous vehicles, quadrotors, ships, airplanes and more. In stationary alignment conditions the platform has zero velocity This information is used as external measurement in the navigation filter to improve the attitude accuracy [9], [10]. Bar-Shalom: INS Fine Alignment With Low-Cost Gyroscopes can be gained into the parameters involved in the FA process in preliminary design process Another measurement update usually applied is zero angular velocity with a version for gyroscopes capable of measuring the earth turn rate [12], [14] and ones which are not capable [15]. Recent papers combining several measurement types includes [17] which used zero velocity, angular velocity and acceleration measurements for a stationary FA process using a tactical grade INS but without including the sensor error terms in the state vector.

FINE ALIGNMENT

OBSERVABILITY ANALYSIS

CONCLUSION