Doubly filtered navigation method

A method of navigating a vehicle by means of a navigation algorithm arranged to determine spatial information on the basis firstly of inertial measurements coming from a signal processor circuit for processing the signals from an inertial measurement unit and secondly of pseudo-distance measurements determined in response to receiving signals from positioning satellites, the signal processor circuit having a calibration input adjustable on a self-calibration value in order to reduce the influence of an error of the inertial measurement unit on the spatial information supplied by the navigation algorithm,

• wherein the navigation algorithm implements at least one set of filters that are Kalman-Schmidt filters arranged to detect faulty measurements among the measurements that are transmitted to the set of filters and to prevent them from being used in determining the spatial information,
• wherein the method comprises the steps of:
• when a journey is completed:
• transmitting the inertial measurements and the pseudo-distance measurements to at least one hybrid navigation filter that is a Kalman filter that is set to supply at least one estimate of at least one error term affecting the inertial measurement unit and of covariance associated with said estimate;
• transmitting each estimate and the associated covariance to a consolidation algorithm programmed to compare the covariance with a first covariance threshold and to store the estimate if the covariance is less than the first covariance threshold;
• and
• storing at least one parameter representative of a utilization condition of the aircraft;
• and
• after the journey has been completed:
• using the consolidation algorithm to verify that the utilization condition is nominal, and where appropriate, updating the self-calibration value by means of the estimate of the error of the inertial measurement unit;
• and
• calibrating the inertial measurement unit by using the updated self-calibration value;
• wherein only one twentieth of the estimate is used to update the self-calibration value.

A method of navigating a vehicle by means of a navigation algorithm arranged to determine spatial information on the basis firstly of inertial measurements coming from a signal processor circuit for processing the signals from an inertial measurement unit and secondly of pseudo-distance measurements determined in response to receiving signals from positioning satellites, the signal processor circuit having a calibration input adjustable on a self-calibration value in order to reduce the influence of an error of the inertial measurement unit on the spatial information supplied by the navigation algorithm,

• wherein the navigation algorithm implements at least one set of filters that are Kalman-Schmidt filters arranged to detect faulty measurements among the measurements that are transmitted to the set of filters and to prevent them from being used in determining the spatial information,
• wherein the method comprises the steps of:
• when a journey is completed:
• transmitting the inertial measurements and the pseudo-distance measurements to at least one hybrid navigation filter that is a Kalman filter that is set to supply at least one estimate of at least one error term affecting the inertial measurement unit and of covariance associated with said estimate;
• transmitting each estimate and the associated covariance to a consolidation algorithm programmed to compare the covariance with a first covariance threshold and to store the estimate if the covariance is less than the first covariance threshold;
• and
• storing at least one parameter representative of a utilization condition of the aircraft;
• and
• after the journey has been completed:
• using the consolidation algorithm to verify that the utilization condition is nominal, and where appropriate, updating the self-calibration value by means of the estimate of the error of the inertial measurement unit;
• and
• calibrating the inertial measurement unit by using the updated self-calibration value,
• wherein if the estimate of the error is greater than a first error threshold, then the estimate of the error is replaced by the value of the first error threshold for updating the self-calibration value, and
• wherein if the estimate of the error is greater than a second error threshold that is greater than the first error threshold, then the estimate of the error is not used for updating the self-calibration value.

A method of navigating a vehicle by means of a navigation algorithm arranged to determine spatial information on the basis firstly of inertial measurements coming from a signal processor circuit for processing the signals from an inertial measurement unit and secondly of pseudo-distance measurements determined in response to receiving signals from positioning satellites, the signal processor circuit having a calibration input adjustable on a self-calibration value in order to reduce the influence of an error of the inertial measurement unit on the spatial information supplied by the navigation algorithm,

• wherein the navigation algorithm being implements at least one set of filters that are Kalman-Schmidt filters arranged to detect faulty measurements among the measurements that are transmitted to the set of filters and to prevent them from being used in determining the spatial information,
• wherein the method comprises the steps of:
• when a journey is completed:
• transmitting the inertial measurements and the pseudo-distance measurements to at least one hybrid navigation filter that is a Kalman filter that is set to supply at least one estimate of at least one error term affecting the inertial measurement unit and of covariance associated with said estimate;
• transmitting each estimate and the associated covariance to a consolidation algorithm programmed to compare the covariance with a first covariance threshold and to store the estimate if the covariance is less than the first covariance threshold;
• and
• storing at least one parameter representative of a utilization condition of the aircraft;
• and
• after the journey has been completed:
• using the consolidation algorithm to verify that the utilization condition is nominal, and where appropriate, updating the self-calibration value by means of the estimate of the error of the inertial measurement unit;
• and
• calibrating the inertial measurement unit by using the updated self-calibration value,
• wherein the vehicle is an aircraft, and the spatial information comprises position, speed, attitude, and protection limit information, and
• wherein the pseudo-distance measurements are transmitted to the hybrid navigation filter only if the speed of the vehicle is greater than a predetermined speed threshold.

A method of navigating a vehicle by means of a navigation algorithm arranged to determine spatial information on the basis firstly of inertial measurements coming from a signal processor circuit for processing the signals from an inertial measurement unit and secondly of pseudo-distance measurements determined in response to receiving signals from positioning satellites, the signal processor circuit having a calibration input adjustable on a self-calibration value in order to reduce the influence of an error of the inertial measurement unit on the spatial information supplied by the navigation algorithm,

• wherein the navigation algorithm implements at least one set of filters that are Kalman-Schmidt filters arranged to detect faulty measurements among the measurements that are transmitted to the set of filters and to prevent them from being used in determining the spatial information, and
• wherein the method comprises the steps of:
• when a journey is completed:
• transmitting the inertial measurements and the pseudo-distance measurements to at least one hybrid navigation filter that is a Kalman filter that is set to supply at least one estimate of at least one error term affecting the inertial measurement unit and of covariance associated with said estimate;
• transmitting each estimate and the associated covariance to a consolidation algorithm programmed to compare the covariance with a first covariance threshold and to store the estimate if the covariance is less than the first covariance threshold;
• and
• storing at least one parameter representative of a utilization condition of the aircraft;
• and
• after the journey has been completed:
• using the consolidation algorithm to verify that the utilization condition is nominal, and where appropriate, updating the self-calibration value by means of the estimate of the error of the inertial measurement unit;
• and
• calibrating the inertial measurement unit by using the updated self-calibration value,
• wherein the vehicle is an aircraft, and the spatial information comprises position, speed, attitude, and protection limit information, and
• wherein atmospheric pressure information is also transmitted to the set of filters and to the hybrid navigation filter.