Identification of Geometric Displacements of Odometers in a GNSS Inertial Navigation System Installed on a Land Vehicle

Identification of geometric displacements of an odometer is understood to be the real-time determination of a lever-arm vector of the odometer relative to an inertial measurement unit, determination of an attitude of the inertial unit relative to the body of a vehicle, and correction of a scale factor of the odometer. A measurement model has been developed for the odometer installed on both controlled front and uncontrolled rear wheels. Observability conditions of the geometric displacements have been considered for trajectories specific for land vehicles. The conditions, when the observability of all three attitude angles of the inertial unit can be achieved, have been discovered. Partial observability of the geometric displacements for the case of the front controlled wheels in the absence of information about a steering wheel rotation has been described. A recurrent procedure for the real-time estimation of observable combinations of the geometric displacements has been developed. Observation equations have been obtained for incorporating the odometer measurements in the observation vector of a coupling filter for a loosely coupled integrated navigation system.