A method to improve the alignment performance for GPS-IMU System

Zero velocity and zero east component of rotation rate relative to local geographic frame have been traditionally applied as measurements for fine alignment of a GPS-IMU system. The performance of the fine alignment, however, will be affected by several types of inertial sensor errors, which could cause part of the Kalman filter states to be unobservable. To overcome this problem, a new method that utilizes the total outputs of the gyro triad and the accelerometer triad as part of the measurements has been proposed by the authors. The initial results have confirmed the effectiveness of the method. In this paper, the observability for both traditional and new alignment methods will be first reviewed. The results from computer simulations will then be presented to compare the traditional and the new alignment methods for the purpose of evaluating the performance of the proposed new method. Data acquired from real inertial sensors will also be applied to assess the traditional and new alignment methods by analyzing their innovation sequences from the Klaman filter. Based on a paper presented at the 18th International Technical Meeting of the Satellite Division of the Institute of Navigation, Long Beach, California, September 2005.