Feasibility study on strapdown stellar-inertial navigation system using star tracker

Abstract

Automated celestial navigation systems based on modern star trackers could serve to augment GPS during normal operations, while also providing an effective navigation alternative in situation where GPS is denied or unavailable. In spite of importance, however, the aided stellar-inertial system has been hardly studied in domestic field. It is continuously required to examine the feasibility of stellar-inertial navigation system. So, this paper discusses the feasibility of strapdown stellar inertial systems as autonomous navigators for spacecraft. Even though proposed stellar-inertial navigation system is used in a spacecraft, it can be expand its application for manned aircraft, ships, and missiles. This study develops an algorithm for the autonomous identification of stars from imaginary image. This algorithm uses a triangle-identification technique, coupled with a optimized parallel search to give an rapid identification of many stars from large catalog with minimal processing and storage requirements. After identifying stars, useful navigation information is extracted from star observations by using vector observation and celestial fix technique. Research for fusing inertial sensor develops a 6-state attitude estimation filter, estimating quaternion as well as gyro biases. And then the smoothing of the measurement are proposed for an unreasonable jump of star tracker. The smoothing algorithm for the rejection of star tracker error jumps is designed by scalar adaptive filter and fuzzy adaptive filter. The validation of proposed algorithms is tested by simulating a spacecraft model. From each simulation results, the system generates position and estimates of quaternion orientation information, without a priori attitude data. Therefore, these techniques provide the basis for strapdown stellar-inertial navigation systems with high precision, reliability, and autonomy.