Methods and systems for implementing an iterated extended Kalman filter within a navigation system

• US 20070213933A1
• Filed: 03/08/2006
• Published: 09/13/2007
• Est. Priority Date: 03/08/2006
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Zeng, Yueping, Kirkland, Jeffrey, Anderson, John, Briske, Richard, Leftin, Lawrence
• Granted Patent: US 7,643,939 B2
• Time in Patent Office: Days
• US Class Current: 701/220
• CPC Class Codes: G01C 21/165 combined with non-inertial navigation instruments
• CPC Class Codes: G01C 21/188 for accumulated errors, e.g. by coupling inertial systems with absolute positioning systems

Abstract

A navigation system for a vehicle is described that includes an inertial measurement unit, a positioning unit, and a processing unit. The inertial measurement unit configured to provide a first set of data relating to operation of the vehicle and the positioning unit is configured to provide a second set of data relating to operation of the vehicle. The processing unit is configured to receive the data sets provided by the inertial measurement unit and the positioning unit and the processing unit comprises an error processing device. The error processing device is programmed with time updating error states and measurement updating error states relating to the data sets received by said processing unit and is configured to iterate both the time updating error states and the measurement updating error states based on a first criteria and iterate only the measurement updating error states based on a second criteria.

Claims

1. A navigation system for a vehicle comprising:

an inertial measurement unit configured to provide a first set of data relating to operation of the vehicle;

a positioning unit configured to provide a second set of data relating to operation of the vehicle; and

a processing unit configured to receive the data sets provided by said inertial measurement unit and said positioning unit, said processing unit comprising an error processing device programmed with time updating error states and measurement updating error states relating to the data sets received by said processing unit, said error processing device configured to iterate both the time updating error states and the measurement updating error states based on a first criteria and iterate only the measurement updating error states based on a second criteria, said processing unit further configured to estimate at least a position and a velocity of the vehicle based on the updated error states.

2. A navigation system according to claim 1 wherein said error processing device comprises a Kalman filter.

3. A navigation system according to claim 1 wherein said inertial measurement unit comprises at least one of a gyroscope and an accelerometer configured to provide acceleration data and angular velocity data for the vehicle.

4. A navigation system according to claim 1 wherein said positioning unit comprises a global positioning system configured to provide position data, velocity data, and altitude data for the vehicle based on pseudo-range measurements.

5. A navigation system according to claim 1 wherein a determination between the first criteria and the second criteria is based on one or more signals received from the vehicle.

6. A navigation system according to claim 5 wherein the signals received from the vehicle comprise one or more of a wheels down signal, a weight on wheels signal, and a brake signal.

7. A navigation system according to claim 1 wherein said processing unit is further configured to receive data from one or more of a barometric altimeter, a true airspeed indicator, and a magnetometer.

8. A navigation system according to claim 1 wherein said processing unit comprises a Kalman filter initialized with at least position and velocity error states.

9. A navigation system according to claim 1 wherein the first criteria comprises data not indicative of a changing position for the vehicle and the second criteria comprises data indicative of a changing position for the vehicle.

10. A method for providing an estimate of position for an object, said method comprising:

receiving sensor data from a plurality of external sources;

determining if the data received from at least one of the external sources is indicative of the object changing position;

iterating measurement updating error states using the received sensor data to determine a position of the object if the data is indicative of a changing position; and

iterating both time updating error states and measurement updating error states using the received sensor data to determine a position of the object if the data is not indicative of a changing position.

11. A method according to claim 10 wherein receiving sensor data from a plurality of external sources comprises receiving sensor data from at least a GPS and an inertial navigation system.

12. A method according to claim 10 wherein determining if the data received from at least one of the external sources is indicative of the object not changing position comprises determining a state of one or more signals received from the object.

13. A method according to claim 10 wherein determining if the data received from at least one of the external sources is indicative of the object changing position comprises comparing a current error state vector with a previous error state vector.

14. A method according to claim 13 wherein comparing a current error state vector with a previous error state vector comprises comparing a gyroscope data and error from a first and a second error state iteration.

15. A method according to claim 10 wherein determining if the data received from at least one of the external sources is indicative of the object changing position comprises determining whether the sensor behavior is linear or non-linear as a function of error magnitude.

16. A method according to claim 15 further comprising calibrating a gyroscope nonlinearity with a time step of a Kalman filter.

17. A method according to claim 10 wherein determining if the data received from at least one of the external sources is indicative of the object changing position comprises determining if the received data is gyroscope compass alignment data.

18. A Kalman filter programmed with time updating error states and measurement updating error states relating to received data sets, said Kalman filter configured to:

iterate both the time updating error states and the measurement updating error states based on a first criteria; and

iterate only the measurement updating error states based on a second criteria.

19. A Kalman filter according to claim 18 wherein the first criteria comprises data not indicative of a changing position for the vehicle and the second criteria comprises data indicative of a changing position for the vehicle.

20. A Kalman filter according to claim 18 the first criteria comprises data indicative of a gyroscope compass alignment mode.