Optimization-based alignment for strapdown inertial navigation system: comparison and extension

In this paper, the optimization-based alignment (OBA) methods are investigated with the main focus on the vector observation construction procedures for the strapdown inertial navigation system (SINS). The contributions of this study are twofold. First, the OBA method is extended to be able to estimate the gyroscope biases coupled with the attitude based on the construction process of the existing OBA methods. This extension transforms the initial alignment into an attitude estimation problem that can be solved by using the nonlinear filtering algorithms. The second contribution is the comprehensive evaluation of the OBA methods and their extensions with different vector observations construction procedures in terms of convergence speed and steady-state estimate by using field test data collected from different grades of SINS. This study is expected to facilitate the selection of appropriate OBA methods for different grades of SINS.