SINS in-motion alignment and position determination for land-vehicle based on quaternion Kalman filter

This paper presents a novel quaternion Kalman filter (NQKF) approach for in-motion alignment of vehicular strapdown inertial attitude reference system using dead-reckoning measurements of inertial measurement unit (IMU) and odometer. Unlike several current techniques, the proposed method eliminates usual linearization procedure of the filtering model and is effective with any initial estimation error. Involving transformation of IMU data and velocity measurement into inertially fixed axes, a set of vector measurements which is defined as the integral of gravitational vector could be constructed simultaneously in body inertial frame and navigation inertial frame from the SINS specific force equation. The INS in-motion alignment is heuristically established as initial attitude determination problem from vector observations. A novel linear quaternion pseudo-measurement model is employed in this paper, because the kinematics equation of quaternion is linear, the combination of the two yields a linear KF for attitude-quaternion estimation using vector measurements. A recursive algorithm for position estimation previous to alignment accomplishment is deduced based on the formula of integration by parts. The calculation result is applied as the position reference in attitude alignment process to diminish gravity deflection. The presented algorithm is verified through experimental data collected from 7500s vehicular test. The in-motion heading alignment accuracy reaches 4' at around 430s and positioning accuracy is about 0.02% of the running distance.