Global Observability Analysis of Aided-INS for UAVs Equipped with Visual Odometry Systems

In this work, observability properties of Inertial Navigation Systems aided with Global Navigation Satellite Systems and Visual Odometry are investigated and applied to the case of UAVs. A global analysis is carried out exploiting the concept of indistinguishable trajectories, that are characterized by solutions of Differential Algebraic Equations. A hybrid formulation is presented to combine two different indistinguishable dynamics, which arise depending on vehicle speed. For particular scenarios commonly encountered in practice, explicit conditions on the system inputs are obtained and appropriately cast as persistency of excitation requirements. With the presented tools, the benefits from Visual Odometry in enhancing observability can be appreciated, in particular w.r.t. attitude and bias estimation, and useful practical indication on the kind of maneuvers making the system observable can be drawn. Assessment of the theoretical results is provided by means of realistic numerical simulations, tailored to the considered UAV application.