Backtracking Velocity Denoising Based Autonomous In-Motion Initial Alignment

In the global navigation satellite system denial environment, strap-down inertial navigation system (SINS) has to rely on the body-frame velocity output by autonomous velocity measurement equipment, such as odometer and Doppler velocity log, to implement the in-motion initial alignment. Considering the external velocity noise and the approximation existing in the body-frame velocity aided initial alignment model, the autonomous in-motion alignment for SINS with high precision is a difficult problem. Besides, the position updating of SINS cannot be realized only depending on the body-frame velocity. The position error will negatively impact the precision of the following fine alignment and navigation. In this paper, a backtracking velocity denoising-based autonomous in-motion initial alignment is proposed. Forward compass alignment and backward compass alignment are carried out, respectively, to denoise the external velocity. Body-frame velocity-based and navigation-frame velocity-based attitude determination are implemented, respectively, to gradually realize the attitude alignment. The contributions of the work presented here are twofold. First, vehicle velocity during the whole initial alignment process is accurately denoised and determined based on the backtracking compass alignment. Second, high precision position alignment is achieved during the attitude determination. The validity of the proposed method is verified based on field test data.