Sensor installation monitoring

• US 10,114,126 B2
• Filed: 04/30/2015
• Issued: 10/30/2018
• Est. Priority Date: 04/30/2015
• Status: Active Grant

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Wu, Shuwu, Li, Ji, Thomas, Tyler, Wan, Howard E.
• Primary Examiner(s): Gregory, Bernarr E
• Application Number:
  US14/701,300
• Publication Number:
  US 20160320493A1
• Time in Patent Office: 1,279 Days
• Field of Search: 34235724
• CPC Class Codes: G01S 19/41 Differential correction, e.g. DGPS [differential GPS]
• CPC Class Codes: G01S 19/44 Carrier phase ambiguity resolution; Floating ambiguity; LAMBDA [Least-squares AMBiguity Decorrelation Adjustment] method
• CPC Class Codes: G01S 19/49 whereby the further system is an inertial position system, e.g. loosely-coupled
• CPC Class Codes: G01S 19/51 Relative positioning
• CPC Class Codes: G01S 19/54 using carrier phase measurements; using long or short baseline interferometry
• CPC Class Codes: G01S 19/55 Carrier phase ambiguity resolution; Floating ambiguity; LAMBDA [Least-squares AMBiguity Decorrelation Adjustment] method

Abstract

Technology for surveying sensor locations on a physical platform is described. An estimated baseline vector can be calculated between a temporary navigation sensor and each fixed navigation sensor in a group of fixed navigation sensors. The temporary navigation sensor can be temporarily placed on the physical platform. The fixed navigation sensors can be installed on the physical platform. A refined baseline vector between the temporary navigation sensor and each fixed navigation sensor can be successively calculated by fixing carrier phase integer ambiguities that are variables used in the estimation of the baseline vector. A final survey distance between the temporary navigation sensor and each of the fixed navigation sensors can be generated using the refined baseline vector.

Claims

1. A method for surveying sensor locations on a physical platform, the method comprising:

under control of at least one hardware processor and memory configured with executable instructions;

receiving signals from a temporary navigation sensor and a group of fixed navigation sensors, the temporary navigation sensor being temporarily placed on the physical platform, the fixed navigation sensors being installed on the physical platform;

using the signals to calculate an estimated baseline vector between the temporary navigation sensor and each fixed navigation sensor in the group of fixed navigation sensors;

successively calculating a refined baseline vector between the temporary navigation sensor and each fixed navigation sensor by fixing carrier phase integer ambiguities that are variables used in the estimation of the baseline vector; and

generating a final survey vector between the temporary navigation sensor and each of the fixed navigation sensors using the refined baseline vector.

2. The method of claim 1, wherein the carrier phase integer ambiguities are successively fixed using an external source.

3. The method of claim 1, wherein the carrier phase integer ambiguities are successively fixed from a longer wavelength to a shortest fixable wavelength in a bootstrap process.

4. The method of claim 1, wherein divergence-free smoothing is continually performed to reduce pseudorange measurement error, thereby enabling successive fixing of the carrier phase integer ambiguities and refining of baseline vectors.

5. The method of claim 1, wherein the carrier phase integer ambiguities are successively fixed in a wavelength order of wide-lane, L2, L1, and up to narrow-lane ambiguities.

6. The method of claim 1, wherein the carrier phase integer ambiguities are successively fixed with high integrity from a longer wavelength to a shortest fixable wavelength in a bootstrap process using the temporary navigation sensor and a subset of fixed navigation sensors.

7. The method of claim 1, wherein the estimated baseline vector between the temporary navigation sensor and each fixed navigation sensor in the group of fixed navigation is determined using an initial survey from an external source.

8. The method of claim 1, further comprising translating the refined baseline vector into a local coordinate system using an attitude of the physical platform when the physical platform is mobile, the attitude being calculated using a high accuracy and integrity source.

9. The method of claim 1, further comprising verifying final survey results on a fixed platform to further ensure high integrity, wherein the verification is performed after final refined baseline vectors and associated carrier phase integer ambiguities are determined, wherein the step of verifying includes:

calculating carrier phase measurement residuals for each pair of navigation sensors;

collecting and analyzing carrier phase residual statistics over a time period; and

performing statistical tests to ensure that the carrier phase measurement residuals comply with an expected distribution given a final survey accuracy.

10. The method of claim 1, further comprising verifying final survey results on a mobile platform to further ensure high integrity, wherein the verification is performed after final refined baseline vectors are determined, wherein the step of verifying includes:

inputting measurements from a plurality of navigation sensors into a Real Time Attitude Determination System (RTAD) algorithm to resolve the carrier phase integer ambiguities with high integrity and an attitude of the mobile platform;

calculating carrier phase measurement residuals for each pair of navigation sensors,

collecting and analyzing carrier phase residual statistics over a time period,

performing statistical tests to ensure that the carrier phase measurement residuals comply with an expected distribution given a final survey accuracy.

11. The method of claim 1, wherein the temporary navigation sensor and the fixed navigation sensors are global positioning systems (GPS) sensors.

12. The method of claim 1, further comprising providing the refined baseline vector to a filter in order to perform error correction.

13. The method of claim 1, further comprising verifying that estimated survey residuals of the refined baseline vector are below a defined threshold.

14. The method of claim 1, wherein the temporary navigation sensor is temporarily placed at a touchdown point within the physical platform.

15. The method of claim 1, wherein the step of calculating the estimated baseline vector is performed using differential global positioning system (GPS) techniques.

16. The method of claim 1, wherein the step of calculating the estimated baseline vector includes using carrier phase measurements and pseudo range measurements from the temporary navigation sensor and each fixed navigation sensor in the group of fixed navigation sensors.

17. The method of claim 1, further comprising removing the temporary navigation sensor from the physical platform after calculation of the refined baseline vector.

18. The method of claim 1, wherein the carrier phase integer ambiguities are corrected in the estimated baseline vector using an external integer ambiguity resolution source, wherein the integer ambiguity source is a real time attitude determination (RTAD) system.

19. The method of claim 1, wherein the step of calculating the refined baseline vector (δ

x) is performed using δ

x=(G^TWG)<sup>−

1</sup>G^TWφ

′

, wherein G is a line of sight geometry matrix, T is a matrix transpose operation, W is a weighting matrix, and φ

′

is an ambiguity-resolved carrier phase measurement.

20. The method of claim 19, wherein φ

′

=φ

−

λ

N=Gδ

x+ε

, wherein φ

=Gδ

x+λ

N+ε

, wherein φ

is an initial carrier phase measurement, λ

is a wavelength of φ

, N is a carrier phase integer ambiguity, and c is measurement error.

21. A method for verifying survey results for sensors on a physical platform, the method comprising:

under control of at least one hardware processor and memory configured with executable instructions;

receiving signals from the sensors on the physical platform, the sensors being mounted on the physical platform;

using the signals to compute an estimated baseline vector between each pair of sensors on the physical platform;

calculating a refined baseline vector between the pair of sensors by correcting carrier phase integer ambiguities in the estimated baseline vector; and

comparing the refined baseline vector to a previously surveyed baseline vector for the pair of sensors, the comparison producing a survey error of the refined baseline vector with respect to the previously surveyed baseline vector.

22. The method of claim 21, wherein the carrier phase integer ambiguities are fixed using a high integrity external source.

23. The method of claim 21, wherein the carrier phase integer ambiguities are successively fixed with high integrity from a longer wavelength to a shortest fixable wavelength in a bootstrap process using a temporary navigation sensor and a subset of fixed navigation sensors.

24. The method of claim 21, further comprising generating an alert when the survey error is not within a predefined threshold.

25. The method of claim 21, wherein the estimated baseline vector is determined using an existing surveyed baseline vector.

26. The method of claim 21, wherein the refined baseline vector indicates a three dimensional (3D) displacement measurement between the pair of sensors.

27. The method of claim 21, wherein the sensors are global positioning system (GPS) sensors that include GPS antennas.

28. The method of claim 21, further comprising translating the refined baseline vector into a local coordinate system using an attitude of the physical platform, the attitude being calculated using a high accuracy attitude source.

29. The method of claim 21, wherein the step of calculating the refined baseline vector (δ

x) is performed using δ

x=(G^TWG)<sup>−

1</sup>G^Twφ

′

, wherein G is a line of sight geometry matrix, T is a matrix transpose operation, W is a weighting matrix, and φ

′

is an ambiguity-resolved carrier phase measurement.

30. The method of claim 21, further comprising providing the survey error to a smoothing filter for a defined period of smoothing time.

31. A method for monitoring flexure of a physical platform, the method comprising:

under control of at least one hardware processor and memory configured with executable instructions;

receiving signals from global positioning system (GPS) sensors on the physical platform, the GPS sensors being mounted on the physical platform;

using the signals to compute an estimated baseline vector between each pair of the GPS sensors on the physical platform;

calculating a refined baseline vector between each pair of the GPS sensors by correcting carrier phase integer ambiguities in the estimated baseline vector, the carrier phase integer ambiguities being fixed using an external source; and

comparing the refined baseline vector to a previously surveyed baseline vector for each pair of the GPS sensors, the comparison producing a time-dependent flexure motion vector between each pair of the GPS sensors.

32. The method of claim 31, further comprising generating an alert when the time-dependent flexure motion vector is not within a predefined threshold.

33. The method of claim 31, further comprising generating an alert when a statistical test indicates that a level of the time-dependent flexure motion is not within a predefined threshold.

34. The method of claim 31, wherein the step of calculating the refined baseline vector (δ

x) is performed using δ

x=(G^TWG)−

1 GTWφ

′

, wherein G is a line of sight geometry matrix, T is a matrix transpose operation, W is a weighting matrix, and φ

′

is an ambiguity-resolved carrier phase measurement.

35. The method of claim 31, further comprising translating the refined baseline vector into a local coordinate system using an attitude of the physical platform, the attitude being calculated using a high accuracy and integrity attitude source.

36. A method for monitoring small relative movement within an otherwise rigid structure or between otherwise relatively stationary structures, the method comprising:

under control of at least one hardware processor and memory configured with executable instructions;

receiving signals from pairs of sensors installed at various surveyed monitoring points on one or more structures;

computing surveyed baseline vector between the pairs of sensors using the signals received from the pairs of sensors;

using the surveyed baseline vector between the pairs of sensors on the one or more structures;

calculating a refined baseline vector between the pair of sensors by correcting carrier phase integer ambiguities in an estimation of baseline vector, the carrier phase integer ambiguities being fixed at an shortest fixable wavelength using a subset of fixed navigation sensors installed on the one or more structures; and

comparing the refined baseline vector to a previously surveyed baseline vector for the pair of sensors, the comparison producing a time-dependent relative motion vector between the two installation points associated with the pair of sensors.

37. The method of claim 36, wherein divergence-free smoothing is continually performed to reduce pseudorange measurement error, thereby enabling carrier phase integer ambiguity fixing at a shortest fixable wavelength.

38. The method of claim 36, wherein the carrier phase integer ambiguities are fixed with high integrity using algorithms and a time-dependent relative motion vector is calculated with high integrity.