A fast in-motion alignment based on inertial frame and reverse navigation

Abstract

Higher alignment accuracy and faster alignment speed are crucial for the whole navigation system. The popular in-motion alignment methods for strapdown inertial navigation system (SINS) are estimation the navigation state error by kalman filter (KF), however, it takes a long time to converge and can't work with large misalignment angle condition. In the paper, a fast alignment method on moving base aided by the speed of b-frame is proposed. First, based on the specific force equation and attitude matrix decomposition, a velocity assisted attitude determination method is derived; Second, a second time alignment scheme is proposed to improve the alignment accuracy by compensating the items, which are omitted in first time alignment; Third, the initial attitude is obtained by reverse navigation using stored data of inertial measurement unit (IMU), and the position information is estimated. At the same time, the omitted items are compensated in second time alignment. Finally, the second time alignment is verified by the simulation and semi-physical simulation. In the sea test, the yaw error is 0.7° in first time alignment and it is reduced to −0.02° in second time alignment within 10 minutes, and accurate position can be provided after alignment.