Observability Analysis of Heading Aided INS for a Maneuvering AUV

Underwater navigation of autonomous underwater vehicles (AUVs) is a challenging task that requires the fusion of multiple sensors used as aiding to the vehicle inertial navigation system. In this paper, we focus on the problem of fusing heading measurements under different maneuvering conditions. We analyze the observability of the heading measurement fusion problem and derive the observable and unobservable subspaces as a function of the AUV's maneuver. Using this analysis, we are able to predict the convergence of the error states for different maneuvers and thus identify the quality of the navigation solution at different mobility patterns. As expected, the results show that the down misalignment error and gyro z-axis bias are always observable. In addition, our results showed that for some maneuvers, the rest of the gyro biases also become observable. Our numerical simulation and sea experiments verify our analytic solutions.