Method for receiver autonomous integrity monitoring and fault detection and elimination

• US 6,864,836 B1
• Filed: 09/05/2003
• Issued: 03/08/2005
• Est. Priority Date: 09/05/2003
• Status: Expired due to Term

• Current Assignee: Deere & Company
• Original Assignee: Navcom Technology, Inc. (Deere & Company)
• Inventors: Hatch, Ronald R., Sharpe, Richard T., Yang, Yunchun
• Primary Examiner(s): PHAN, DAO LINDA
• Application Number:
  US10/656,956
• Publication Number:
  US 20050052319A1
• Time in Patent Office: 550 Days
• Field of Search: 342/357.06, 342/357.15, 342/357.12, 342/352, 702/57, 702/58, 702/116, 702/183, 701/207, 701/213
• US Class Current: 342/357.58
• CPC Class Codes: G01S 19/20 Integrity monitoring, fault detection or fault isolation of space segment

Abstract

A method for detecting and identifying a faulty measurement among a plurality of GPS measurements, obtained by a GPS receiver with respect to a plurality of satellites in view of the GPS receiver, determines whether the plurality of GPS measurements include a faulty measurement. In response to a determination that the plurality of GPS measurements include a faulty measurement, the method identifies a satellite contributing the faulty measurement by computing a correlation value associated with each of the plurality of satellites, and selecting a satellite associated with a highest correlation value as the satellite contributing the faulty measurement.

Claims

1. A method for identifying a faulty measurement among a plurality of GPS range measurements that are used to determine a state of a discrete-time controlled process, comprising:

computing a plurality of correlation values, each correlation value associated with one of the plurality of GPS measurements obtained by a GPS receiver with respect to a plurality of satellites, each of the plurality of GPS measurements corresponding to one of the plurality of satellites; and

selecting a GPS measurement among the plurality of GPS measurements as the faulty measurement based on the correlation values.

2. The method of claim 1 wherein the correlation values represent a correlation between residuals of the plurality of measurements and residuals corresponding to a change in one of the plurality of measurements while the rest of the plurality of measurements are unchanged.

6. The method of claim 1 wherein selecting a measurement among the plurality of measurements as the faulty measurement comprises:

identifying a highest correlation value; and

selecting a measurement associated with the highest correlation value as the faulty measurement.

7. The method of claim 6, wherein selecting the measurement associated with the highest correlation value as the faulty measurement comprises:

identifying a second highest correlation value; and

selecting the measurement associated with the highest correlation value as the faulty measurement when the difference between the highest correlation value and the second highest correlation value exceeds a predetermined threshold value.

8. The method of claim 6 wherein selecting the measurement associated with the highest correlation value as the faulty measurement comprises:

determining that the highest correlation value exceeds a first predetermined threshold value;

identifying a second highest correlation value; and

determining that the second highest correlation value is smaller than the first predetermined threshold value and the difference between the first predetermined threshold value and the second highest correlation value exceeds a second predetermined threshold value.

9. The method of claim 1 wherein the number of the plurality of satellites is greater than 5.

10. The method of claim 1, further comprising:

determining a size of an error in the faulty measurement.

11. The method of claim 10 wherein determining the size of the error in the faulty measurement comprises:

dividing a root mean square residual of the plurality of measurements by a root mean square residual corresponding to a unit change in the one of the plurality of measurements while the rest of the plurality of measurements are unchanged.

12. The method of claim 10 wherein determining the size of the error in the faulty measurement comprises:

dividing a root mean square residual of the plurality of measurements by a square root of a diagonal element corresponding to the faulty measurement in a residual sensitivity matrix.

3. A method for identifying a faulty measurement among a plurality of measurements that are used to determine a state of a discrete-time controlled process, comprising:

computing a plurality of correlation values, each correlation value associated with one of the plurality of measurements;

the computing of the correlation values including;

computing a residual sensitivity matrix;

computing residuals corresponding to the plurality of measurements; and

computing a correlation coefficient associated with the one of the plurality of measurements based on the residuals of the plurality of measurements and the residual sensitivity matrix; and

selecting a measurement among the plurality of measurements as the faulty measurement based on the correlation values.

4. The method of claim 3 wherein computing the residuals corresponding to the plurality of measurements comprises:

obtaining a least-squares solution of the state of the discrete-time controlled process;

computing expected values of the plurality of measurements based on the least-square solution; and

computing differences between the plurality of measurements and the expected values of the plurality of measurements.

5. The method of claim 3 wherein the residuals corresponding to the plurality of measurements are computed using the residual sensitivity matrix.

13. A method for detecting and identifying a faulty measurement among a plurality of GPS measurements obtained by a GPS receiver with respect to a plurality of satellites, comprising:

determining whether the plurality of GPS measurements include a faulty measurement; and

in response to a determination that the plurality of GPS measurements include a faulty measurement, identifying a satellite contributing the faulty measurement by;

computing a plurality of correlation values, each correlation value associated with one of the plurality of satellites; and

selecting a satellite among the plurality of satellites as the satellite contributing the faulty measurement based on the correlation values.

14. The method of claim 13 wherein determining whether the GPS measurements include a faulty measurement comprises:

computing a test statistic using post-fix residuals corresponding to the plurality of GPS measurements; and

determining whether the test statistic exceeds a fault threshold.

15. The method of claim 14 wherein the fault threshold is a function of a navigation mode used by the GPS receiver.

16. The method of claim 14, further comprising:

determining a size of an error in the faulty measurement.

17. The method of claim 16, further comprising:

verifying that the satellite contributing to the faulty measurement has been correctly identified.

18. The method of claim 17, wherein verifying that the satellite contributing to the faulty measurement has been correctly identified comprises:

adjusting the post-fix residuals based on the size of the error in the faulty measurement;

computing the test statistic using the adjusted post-fix residuals; and

verifying that the test statistic does not exceed the fault threshold.

19. The method of claim 13 wherein computing the correlation value associated with a respective satellite comprises:

computing a residual sensitivity matrix;

computing residuals corresponding to the plurality of GPS measurements; and

computing a correlation coefficient associated with the respective satellite based on the residuals and the residual sensitivity matrix.

20. The method of claim 13 wherein selecting a satellite among the plurality of satellites as the satellite contributing the faulty measurement comprises:

identifying a highest correlation value; and

selecting the satellite associated with the highest correlation value as the satellite contributing the faulty measurement.

21. A computer readable medium comprising computer executable program instructions that when executed by a processor in a digital processing system, causes the digital processing system to perform the operations of:

computing a plurality of correlation values, each correlation value associated with one of the plurality of GPS range measurements obtained by a GPS receiver with respect to a plurality of satellites, each of the plurality of GPS measurements corresponding to one of the plurality of satellites; and

selecting the GPS range measurement associated with a highest correlation value among the plurality of correlation values as a faulty measurement.

22. The computer readable medium of claim 21 wherein the method further comprises:

determining a size of an error in the faulty measurement.

23. A computer-readable medium containing thereon instructions, which, when executed by a processor in a digital processing system, causes the digital processing system to determine a state of a discrete-time controlled process by performing the operations of:

computing a plurality of correlation values, each correlation value associated with one of a plurality of GPS range measurements obtained by a GPS receiver with respect to a plurality of satellites, each of the plurality of GPS measurements corresponding to one of the plurality of satellites; and

selecting a GPS measurement among the plurality of GPS measurements as a faulty measurement based on the correlation values.

24. The computer-readable medium of claim 23 wherein the operations that the instructions cause the digital processing system to perform further comprise:

determining a size of an error in the faulty measurement.

25. The computer-readable medium of claim 24 wherein determining the size of the error in the faulty measurement comprises:

dividing a root mean square residual of the plurality of measurements by a root mean square residual corresponding to a unit change in one of the plurality of measurements while the rest of the plurality of measurements are unchanged.

26. The computer-readable medium of claim 24 wherein determining the size of the error in the faulty measurement comprises:

dividing a root mean square residual of the plurality of measurements by a square root of a diagonal element corresponding to the faulty measurement in a residual sensitivity matrix.

27. The computer readable medium of claim 23 wherein the correlation values represent a correlation between residuals of the plurality of measurements and residuals corresponding to a change in the one of the plurality of measurements while the rest of the plurality of measurements are unchanged.

31. The computer-readable medium of claim 23 wherein selecting a measurement among the plurality of measurements as the faulty measurement comprises:

identifying a highest correlation value; and

selecting the measurement associated with the highest correlation value as the faulty measurement.

32. The computer-readable medium of claim 31, wherein selecting the measurement associated with the highest correlation value as the faulty measurement comprises:

identifying a second highest correlation value; and

selecting the measurement associated with the highest correlation value as the faulty measurement when the difference between the highest correlation value and the second highest correlation value exceeds a predetermined threshold value.

33. The computer-readable medium of claim 31 wherein selecting the measurement associated with the highest correlation value as the faulty measurement comprises:

determining that the highest correlation value exceeds a first predetermined threshold value;

identifying a second highest correlation value; and

determining that the second highest correlation value is smaller than the first predetermined threshold value and the difference between the first predetermined threshold value and the second highest correlation value exceeds a second predetermined threshold value.

34. The computer-readable medium of claim 23 wherein the number of the plurality of satellites is greater than 5.

28. A computer-readable medium containing thereon instructions, which, when executed by a processor in a digital processing system, causes the digital processing system to determine a state of a discrete-time controlled process by performing the operations of:

computing a plurality of correlation values each correlation value associated with one of a plurality of measurements, the computing of the correlation values including;

computing a residual sensitivity matrix;

computing residuals corresponding to the plurality of measurements; and

computing a correlation coefficient associated with the one of the plurality of measurements based on the residuals of the plurality of measurements and the residual sensitivity matrix; and

selecting a measurement among the plurality of measurements as the faulty measurement based on the correlation values.

29. The computer-readable medium of claim 28 wherein computing the residuals corresponding to the plurality of measurements comprises:

obtaining a least-squares solution of a state of a discrete-time controlled process;

computing expected values of the plurality of measurements based on the least-square solution; and

computing differences between the plurality of measurements and the expected values of the plurality of measurements.

30. The computer-readable medium of claim 28 wherein the residuals corresponding to the plurality of measurements are computed using the residual sensitivity matrix.

35. A system capable of identifying a faulty measurement among a plurality of GPS range measurements that are used to determine a state of a discrete-time controlled process, comprising:

a processor;

a memory including instructions, which, when executed by the processor, causes the processor to perform the operations of;

computing a plurality of correlation values, each correlation value associated with one of the plurality of GPS measurements obtained by a GPS receiver with respect to a plurality of satellites, each of the plurality of GPS measurements corresponding to one of the plurality of satellites; and

selecting a GPS measurement among the plurality of GPS measurements as the faulty measurement based on the correlation values.

36. The system of claim 35 wherein the correlation values represent a correlation between residuals of the plurality of measurements and residuals corresponding to a change in the one of the plurality of measurements while the rest of the plurality of measurements are unchanged.

40. The system of claim 35 wherein selecting a measurement among the plurality of measurements as the faulty measurement comprises:

identifying a highest correlation value; and

selecting the measurement associated with the highest correlation value as the faulty measurement.

41. The system of claim 40, wherein selecting the measurement associated with the highest correlation value as the faulty measurement comprises:

identifying a second highest correlation value; and

selecting the measurement associated with the highest correlation value as the faulty measurement when the difference between the highest correlation value and the second highest correlation value exceeds a predetermined threshold value.

42. The system of claim 40 wherein selecting the measurement associated with the highest correlation value as the faulty measurement comprises:

determining that the highest correlation value exceeds a first predetermined threshold value;

identifying a second highest correlation value; and

determining that the second highest correlation value is smaller than the first predetermined threshold value and the difference between the first predetermined threshold value and the second highest correlation value exceeds a second predetermined threshold value.

43. The system of claim 35 wherein the number of the plurality of satellites is greater than 5.

44. The system of claim 35, wherein the operations further comprise:

determining a size of an error in the faulty measurement.

45. The system of claim 44 wherein determining the size of the error in the faulty measurement comprises:

dividing a root mean square residual of the plurality of measurements by a root mean square residual corresponding to a unit change in one of the plurality of measurements while the rest of the plurality of measurements are unchanged.

46. The system of claim 44 wherein determining the size of the error in the faulty measurement comprises:

dividing a root mean square residual of the plurality of measurements by a square root of a diagonal element corresponding to the faulty measurement in a residual sensitivity matrix.

37. A system capable of identifying a faulty measurement among a plurality of measurements that are used to determine a state of a discrete-time controlled process, comprising:

a processor;

a memory including instructions, which, when executed by the processor, causes the processor to perform the operations of;

computing a plurality of correlation values, each correlation value associated with one of the plurality of measurements, the computing of the correlation values including;

computing a residual sensitivity matrix;

computing residuals corresponding to the plurality of measurements; and

computing a correlation coefficient associated with the one of the plurality of measurements based on the residuals of the plurality of measurements and the residual sensitivity matrix; and

selecting a measurement among the plurality of measurements as the faulty measurement based on the correlation values.

38. The system of claim 37 wherein computing the residuals corresponding to the plurality of measurements comprises:

obtaining a least-squares solution of the state of the discrete-time controlled process;

computing expected values of the plurality of measurements based on the least-square solution; and

computing differences between the plurality of measurements and the expected values of the plurality of measurements.

39. The system of claim 37 wherein the residuals corresponding to the plurality of measurements are computed using the residual sensitivity matrix.

47. A system for identifying a faulty measurement among a plurality of GPS range measurements that are used to determine a state of a discrete-time controlled process, comprising:

means for computing a plurality of correlation values, each correlation value associated with one of the plurality of GPS measurements obtained by a GPS receiver means with respect to a plurality of satellites, each of the plurality of GPS measurements corresponding to one of the plurality of satellites; and

means for selecting a GPS measurement among the plurality of GPS measurements as the faculty measurement based on the correlation values.