A Study on in-Flight Alignment Methods and Error Modelling of Strapdown Inertial Navigation Systems (SINS)

Strapdown Inertial Navigation System (SINS) is a critical technology for aircraft, ships, vehicles, and rockets to navigate and position themselves. For proper navigational information to be obtained, SINS must first be aligned. The alignment process consists of calculating the transformation matrix from the body frame to the computation frame to minimize the misalignment error between the body frame and the computation frame. SINS can be initially aligned either on the ground or in flight. In-flight alignment methods are becoming more popular in practice. However, errors induced by variables such as sensor noise, temperature fluctuations, and vibrations can degrade SINS performance. To reduce these inaccuracies and increase the accuracy of SINS, in-flight alignment procedures and error modelling approaches have been developed. This study gives a brief overview of SINS in-flight alignment methods and error modelling methodologies. In-flight alignment technologies such as the Kalman filter and the attitude and heading reference system are thoroughly explored, along with their benefits and drawbacks. Error modelling techniques, including the use of error models, covariance matrices, and fault detection and isolation algorithms, are also reviewed. The paper concludes that in-flight alignment methods and error modelling techniques are essential for improving the accuracy of SINS. While the choice of method may depend on the specific application and requirements, the use of advanced techniques such as the Kalman filter and fault detection algorithms can significantly enhance the performance of SINS.