Velocity-plus-rate matching for improved tactical weapon rapid transfer alignment

Abstract

An improved rapid transfer alignment algorithm formulation is presented. This improvement takes advantage of angular rate data, available from strapdown aircraft Inertial Navigation Systems (INS), as measurements for updating a weapon strapdown INS via a Kalman filter based alignment algorithm. The two INS's are mounted to a common but flexible structure. The improved formulation overcomes limitations identified in a previous study, which used attitude measurements, to achieve rapid transfer alignment. Those limitations include a lack of weapon INS instrument calibration. The present formulation provides improved attitude and instrument calibration estimates as will be shown by monte carlo simulation results. These simulation results demonstrate attitude alignment errors less than 1.5 milliradians about the maneuver axis and less than 1 milliradian for the other axes, while providing gyro instrument calibration, These results are achieved using a 9 state Kalman filter, with combinations of 6 measurements, 3 velocity and 3 rate, operated at a 20 Hz measurement update cycle.