APPARATUS AND METHODS FOR DRIFTLESS ATTITUDE DETERMINATION AND RELIABLE LOCALIZATION OF VEHICLES

• US 20120086598A1
• Filed: 10/08/2010
• Published: 04/12/2012
• Est. Priority Date: 10/08/2010
• Status: Abandoned Application

• Current Assignee: Canadian Space Agency (Government of Canada)
• Original Assignee: Canadian Space Agency (Government of Canada)
• Inventors: Aghili, Farhad
• Application Number:
  US12/901,150
• Publication Number:
  US 20120086598A1
• Time in Patent Office: Days
• US Class Current: 342/357.25
• CPC Class Codes: G01S 19/43 using carrier phase measurements, e.g. kinematic positioning; using long or short baseline interferometry
• CPC Class Codes: G01S 19/47 the supplementary measurement being an inertial measurement, e.g. tightly coupled inertial
• CPC Class Codes: G01S 19/54 using carrier phase measurements; using long or short baseline interferometry

Abstract

In order to determine positional information, about a mobile robot, Real Time Kinematic (RTK) Global Satellite Navigation System (GNSS) measurement data are obtained by at least two GNSS receivers mounted on the mobile robot. Estimates of the covariance matrices of the measurement data are computed. The RTK GNSS measurement data are combined according to the covariance matrices to obtain enhanced positional information. The results may be fused with data from an IMU to obtain driftless attitude and/or localization information.

Claims

1. A method of determining positional information about a vehicle, comprising:

computing estimates of the covariance matrices of Real Time Kinematic (RTK) Global Satellite Navigation System (GNSS) measurement data obtained by at least two GNSS receivers mounted on the vehicle; and

fusing the RTK GNSS measurement data according to their corresponding covariance matrices to obtain enhanced positional information.

2. The method of claim 1, wherein an antenna-to-antenna baseline is defined between the GNSS receivers, and the estimates of the covariance matrices are based on the error in the magnitude of a measurement of the antenna-to-antenna baseline and the confidence in the GNSS receiver measurements.

4. The method of claim 2, wherein the measurement data from the RTK GNSS receivers is fused with measurement data from an inertial measurement unit (IMU).

5. The method of claim 4, wherein the IMU includes an onboard accelerometer and rate gyro.

6. The method of claim 4, wherein the IMU includes an onboard inclinometer and rate gyro.

7. The method of claim 4, wherein the measurement data is fused in a Kalman filter.

8. The method of claim 7, wherein the positional information comprises attitude information obtained from the Kalman filter.

9. The method of claim 8, wherein the attitude information is derived from the quaternion

10. The method of claim 7, wherein the positional information also comprises localization information.

11. The method of claim 10, wherein the localization information is derived from the equation

12. The method of claim 4, wherein the covariance matrix of the GNSS measurement noise is derived from equation

13. The method of claim 7, wherein the initial states of the Kalman filter are determined from difference between the two GNSS measurements and the accelerometer measurement.

14. The method of claim 4, further comprising computing an observation vector from measurements obtained from the accelerometer and the GNSS receivers, and applying the observation vector, the estimates of the covariance matrices and measurements obtained from the onboard rate gyro as inputs to a Kalman filter to determine the attitude of the vehicle.

15. The method of claim 1, wherein at least three GNSS receivers are mounted on the vehicle and a pose estimation is obtained from measurements from the three GNSS receivers.

16. The method of claim 1, wherein the GNSS receivers compute their ranges with respect to a stationary GNSS base station.

3. The method of claim2, wherein the antenna-to-antenna baseline is not collinear with the vector of gravity.

17. An apparatus for determining positional information about a vehicle, comprising:

at least two GNSS receivers for mounting on the vehicle and defining an antenna-to-antenna baseline therebetween; and

a processor configured to compute estimates of the covariance matrices of Real Time Kinematic (RTK) Global Satellite Navigation System (GNSS) measurement data obtained by at least two GNSS receivers mounted on the mobile robot, and to fuse the RTK GNSS measurement data according to their corresponding covariance matrices to obtain enhanced positional information.

18. The apparatus of claim 17, wherein an antenna-to-antenna baseline is defined between the GNSS receivers, and the estimates of the covariance matrices are based on the error in the magnitude of a measurement of the antenna-to-antenna baseline and the confidence in the GNSS receiver measurements.

19. The apparatus of claim 18, wherein an antenna-to-antenna baseline is not collinear with the vector of gravity.

20. The apparatus of claim 17, wherein the processor is configured to fuse measurement data from the RTK GNSS receivers with measurement data from an inertial measurement unit (IMU).

21. The apparatus of claim 20, wherein the IMU includes an onboard accelerometer and rate gyro.

22. The apparatus of claim 20, wherein the IMU includes an onboard inclinometer and rate gyro

23. The apparatus of claim 20, wherein the processor comprises a Kalman filter.

24. The apparatus of claim 23, wherein the Kalman filter is configured to produce attitude information about the vehicle.

25. The apparatus of claim 24, wherein the attitude information is derived from the equation

26. The apparatus of claim 24, wherein the positional information also comprises localization information.

27. The apparatus of claim 26, wherein localization information is derived from the equation

28. The apparatus of claim 23, wherein the initial states of the Kalman filter is determined from the difference between GPS measurements and the accelerometer measurement.

29. The apparatus of claim 21, comprising a module for computing an observation vector from measurements obtained from the accelerometer and the GPS receivers, and a Kalman filter receiving as inputs the observation vector, the estimates of the covariance matrices and measurements obtained from the onboard rate gyro and outputting the attitude of the mobile robot.

30. The apparatus of claim 17, comprising at least three GNSS receivers mounted on the mobile robot, and wherein the processor is configured to obtain a pose estimation from measurements from the two GPS receivers.

31. The apparatus of claim 17, wherein the GNSS receivers are configured to compute their ranges with respect to a stationary GNSS base station.

32. An apparatus for determining positional information about a vehicle, comprising:

at least two GNSS receivers for mounting on the vehicle and defining an antenna-to-antenna baseline therebetween;

an inertial Measurement Unit (IMU) for obtaining data about the movement of the mobile robot; and

a processor configured to and to fuse the RTK GNSS measurement data and the data from the IMU to obtain enhanced positional information.

33. The apparatus of claim 32, wherein the processor is configured to compute estimates of the covariance matrices of Real Time Kinematic (RTK) Global Satellite Navigation System (GNSS) measurement data obtained by at least two GNSS receivers mounted on the vehicle and to fuse the RTK GNSS measurement data according to their corresponding covariance matrices.

34. The apparatus of claim 32, wherein the vehicle is a mobile robot or a walking robot or a humanoid robot.