A robust astro-inertial integrated navigation algorithm based on star-coordinate matching

The astro-inertial integrated navigation system has the characteristic of anti-electromagnetic interference but suffers from aero-optical starlight perturbation when applied to hypersonic cruise vehicles (HCVs). Because there is no strategy in the traditional loosely coupled astro-inertial integration framework for recognising and evaluating skew in star observation, this system cannot adapt to perturbations, and the navigation accuracy tends to degrade. In this study, a strongly coupled framework for an astro-inertial integrated system is designed, and a robust astro-inertial fusion algorithm based on star-coordinate matching is proposed; the skew degree of each observed star is quantified by matching with the virtual star image re-established from INS measurements. Based on star-coordinate matching, a robust weight-tuning rule is designed according to the maximum-likelihood estimation theory, including a method to determine the star-coordinate confidence scope by statistically analysing the astronomical-observation perturbation rate. Compared with the traditional loosely coupled astro-inertial integration framework, the proposed strongly coupled framework and robust astro-inertial integrated navigation algorithm based on star-coordinate matching can significantly improve robustness against perturbations.