METHODS OF ATTITUDE AND MISALIGNMENT ESTIMATION FOR CONSTRAINT FREE PORTABLE NAVIGATION

• US 20120245839A1
• Filed: 03/22/2012
• Published: 09/27/2012
• Est. Priority Date: 03/23/2011
• Status: Active Grant

• Current Assignee: Trusted Positioning Inc. (TDK Corporation)
• Original Assignee: Trusted Positioning Inc. (TDK Corporation)
• Inventors: Syed, Zainab, Noureldin, Aboelmagd, El-Sheimy, Naser, Georgy, Jacques, Goodall, Christopher, Atia, Mohamed
• Granted Patent: US 10,203,207 B2
• Time in Patent Office: Days
• US Class Current: 701/408
• CPC Class Codes: G01C 21/1654 with electromagnetic compass
• CPC Class Codes: G01C 21/206 specially adapted for indoor navigation
• CPC Class Codes: G01C 25/005 initial alignment, calibration or starting-up of inertial devices

Abstract

The present disclosure relates to methods of enhancing a navigation solution about a device and a platform, wherein the mobility of the device may be constrained or unconstrained within the platform, and wherein the navigation solution is provided even in the absence of normal navigational information updates (such as, for example, GNSS). More specifically, the present method comprises utilizing measurements from sensors (e.g. accelerometers, gyroscopes, magnetometers etc.) within the device to calculate and resolve the attitude of the device and the platform, and the attitude misalignment between the device and the platform.

Claims

1. A method for enhancing a navigation solution of a device and a platform, wherein the mobility of the device is constrained or unconstrained within the platform, the method comprising:

detecting and estimating the attitude of the device and the platform, and determining the misalignment between the device and the platform.

2. The method of claim 1, wherein the platform is a vehicle, a vessel or a person.

3. A method for enhancing a navigation solution of a device and a platform, wherein the mobility of the device is constrained or unconstrained within the platform and wherein the device comprises at least three accelerometers, wherein said accelerometers have quality specifications, the method comprising:

detecting and estimating the attitude of the device and the platform, and determining the misalignment between the device and the platform, by calculating roll and pitch of the device using specific forces measured at the device, and calculating the standard deviation of the roll and pitch of the device using the specific forces measured at the device and the quality specifications of the at least three accelerometers.

4. The method of claim 3, wherein the method further comprises removing high frequency noise from the specific forces measured using a low pass filter.

5. The method of claim 3, wherein the quality specifications of the at least three accelerometers are given in terms of velocity random walk parameter.

6. The method of claim 3, wherein the quality specifications of the at least three accelerometers are determined empirically.

7. The method of claim 6, wherein the empirical determination is performed using an Allan Variance technique.

64. The methods in anyone of claims 3, 8, 36, 37, 38, 43, 50, 62, 63 or any combination thereof, wherein the calculated attitude and misalignment between the device and the platform is used to enhance the navigation solution.

8. A method for enhancing a navigation solution of a device and a platform, wherein the mobility of the device is constrained or unconstrained within the platform, the method comprising:

detecting and estimating the attitude of the device and the platform, and determining the misalignment between the device and the platform, by estimating the absolute heading of the platform and the standard deviation thereof by using the time rate of change of received signal strength (RSS) of wireless signals from a wireless communication system having at least one access point.

9. The method of claim 8, wherein the wireless signals are from a WiFi network.

10. The method of claim 8, wherein the method further comprises reducing noise of the RSS of the wireless signals.

11. The method of claim 8, wherein the method comprises the following steps:

a) Obtaining the position coordinates of the device;

b) Obtaining the distance traveled by the platform until a threshold distance is obtained;

c) Measuring the RSS of the wireless signals from the at least one access point at the device during the time the distance is traveled by the platform;

d) Obtaining the location of the at least one access point having the RSS of the wireless signals detected at the device;

e) Calculating the rate of change of the RSS of the wireless signals for the distance traveled by the platform;

f) Utilizing the calculated rate of change of the RSS of the wireless signals to determine an access point angle from each at least one access point to the platform;

g) Utilizing the access point angles to estimate heading ranges of the platform; and

h) Estimating the absolute heading of the platform utilizing the estimated heading ranges and calculating the standard deviation for the absolute heading of the platform.

12. The method of claim 11, wherein the position coordinates of the device are obtained from the navigation solution of the device.

13. The method of claim 11, wherein the location of the at least one access point is obtained from a database.

14. The method of claim 11, wherein the method further comprises reducing noise of the RSS of the wireless signals.

15. The method of claim 11, wherein the method further comprises utilizing a clustering technique to filter out outliner access point angles.

16. The method of claim 15, wherein the clustering technique used is k-mean clustering algorithm.

17. The method of claim 8, wherein the method utilizes a measurement-based estimation technique to obtain velocity of the platform and standard deviations thereof.

18. The method of claim 17, wherein the method utilizes the velocity of the platform and the standard deviations thereof to calculate the absolute heading of the platform and the standard deviation thereof.

19. The method of claim 17 or 18, wherein the measurement-based estimation technique is a Maximum Likelihood based technique or a Least Squares based technique.

20. The method of claims 17 and 18, wherein the method further comprises the following steps:

a) Measuring and saving the RSS of the wireless signals from the at least one access point at the device;

b) Obtaining the location of the at least one access points having the RSS of the wireless signals detected at the device;

c) Calculating the time rate of change of the RSS of the wireless signals;

d) Obtaining the position coordinates of the device;

e) Applying the measurement-based estimation technique to estimate the velocity of the platform and the standard deviations thereof; and

f) Estimating the absolute heading of the platform and standard deviations thereof using the velocity of the platform and the standard deviations thereof.

21. The method of claim 20, wherein the location of the at least one access point is obtained from a database.

22. The method of claim 20, wherein the position coordinates of the device are obtained from the navigation solution of the device.

23. The method of claim 20, wherein the method further comprises reducing noise of the RSS of the wireless signals.

24. The method of claim 20, wherein the measurement-based estimation technique is a Maximum Likelihood based technique or a Least Squares based technique.

25. The method of claim 8, wherein the absolute heading of the platform and standard deviations thereof is estimated using a measurement-based estimation technique.

26. The method of claim 25, wherein the measurement-based estimation technique is a Maximum Likelihood based technique or a Least Squares based technique.

27. The method of claim 25, wherein the method comprises the following steps:

a) Measuring and saving the RSS of the wireless signals from the at least one access point at the device;

b) Obtaining the location of the at least one access point having the RSS of the wireless signals detected at the device;

c) Calculating the time rate of change of the RSS of the wireless signals;

d) Obtaining the position coordinates of the device;

e) Obtaining the speed of the platform from the navigation solution on the device or from any other source of speed readings if available;

f) Calculating an angle of arrival from the at least one access points to the device or measuring it if such a measurement is available; and

g) Applying the measurement-based estimation technique to estimate the absolute heading of the platform heading and standard deviations thereof.

28. The method of claim 27, wherein the location of the at least one access point are obtained from a database.

29. The method of claim 27, wherein the position coordinates of the device are obtained from the navigation solution of the device.

30. The method of claim 27, wherein the method further comprises reducing noise of the RSS of the wireless signals.

31. The method of claim 27, wherein the measurement-based estimation technique is a Maximum Likelihood based technique or a Least Squares based technique.

32. The method of claim 8, wherein the method consists of the following steps:

a) Measuring and saving the RSS of the wireless signals from the at least one access point at the device;

b) Obtaining the location of the at least one access point having the RSS of the wireless signals detected at the device;

c) Calculating the time rate of change of the RSS of the wireless signals;

d) Obtaining the position coordinates of the device;

e) Obtaining the speed of the platform from the navigation solution on the device or from any other source of speed readings if available;

f) Calculating an angle of arrival from the at least one access points to the device or measuring it if such a measurement is available;

g) Calculating a possible platform heading for each at least one access points whose RSS of the wireless signals is available to the device; and

h) Estimating the absolute heading of the platform as a function of each of the possible platform headings and calculating the standard deviation of the absolute heading of the platform from the standard deviations of the possible platform headings.

33. The method of claim 32, wherein the locations of the access points having RSS available to the device are obtained from a database.

34. The method of claim 32, wherein the position coordinates of the device are obtained from the navigation solution of the device.

35. The method of claim 32, wherein the method further comprises reducing noise of the RSS of the wireless signals.

36. A method for enhancing a navigation solution of a device and a platform, wherein the mobility of the device is constrained or unconstrained within the platform, the method comprising:

detecting and estimating the attitude of the device and the platform, and determining the misalignment between the device and the platform, by estimating initial misalignment of heading between the device and the platform when a source of absolute velocity is available.

37. A method for enhancing a navigation solution of a device and a platform, wherein the mobility of the device is constrained or unconstrained within the platform, the method comprising:

detecting and estimating the attitude of the device and the platform, and determining the misalignment between the device and the platform, by estimating initial misalignment of heading between the device and the platform when a source of absolute velocity is available, by using information from the source of absolute velocity and assuming candidates of initial misalignment to determine candidate specific forces at the device and comparing the candidate specific forces to specific forces measured by the device.

38. A method for enhancing a navigation solution of a device and a platform, wherein the mobility of the device is constrained or unconstrained within the platform and wherein the device comprises at least three accelerometers, the method comprising:

detecting and estimating the attitude of the device and the platform, and determining the misalignment between the device and the platform, by estimating misalignment of heading between the device and the platform independent of the availability of absolute source of velocity or heading information.

39. The method of claim 38, wherein the misalignment of heading between the device and the platform is estimated empirically, using mathematical relationships, or a combination thereof.

40. The method of claim 39, wherein the empirical estimation is performed based on using information from the at least three accelerometers or using pitch and roll of the device.

41. The method of claim 38, wherein the misalignment of heading between the device and the platform is estimated using mathematical relationships.

42. The method of claim 41, wherein the mathematical relationships are selected from the group consisting of any one or any combination of signal mean, mean energy, spectral density, circular convolution, and principle component analysis to detect the forward axis or the misalignment between the device and platform.

43. A method for enhancing a navigation solution of a device and a platform, wherein the mobility of the device is constrained or unconstrained within the platform, the method comprising:

detecting and estimating the attitude of the device and the platform, and determining the misalignment between the device and the platform, by calculating continued misalignment of heading between the device and the platform when a source of absolute velocity or heading information is available or interrupted.

44. The method of claim 43, wherein the method further comprises obtaining absolute heading of the platform from one of the following:

(a) the source of absolute velocity,

(b) predicted velocity values, wherein the predicted velocity values are obtained from the navigation solution, where the source of absolute velocity is temporarily interrupted,

(c) filtered velocity values, wherein the filtered velocity values are estimated from the navigation solution, when the source of absolute velocity is available,

(d) Using RSS of wireless signals from wireless communication systems,

(e) Using maps of the environment, or

(f) Using any combination of a) to e) above.

45. The method of claim 44, wherein method further comprises calculating standard deviations of the absolute heading of the platform.

46. The method of claim 43, wherein the method further comprises obtaining absolute heading of the device from one of the following:

(a) Using calculations from an integrated navigation solution of the device;

(b) Using calculations from an inertial mechanization aided by absolute pitch and roll of the device;

(c) Using calculations, wherein said calculations are obtained from a leveled synthetic gyroscope obtained by using absolute pitch and roll of the device;

(d) Using calculations, wherein said calculations are obtained from readings of a leveled magnetometer obtained by using absolute pitch and roll;

or

(e) Using calculations, wherein said calculations are obtained from a blended solution between two absolute device headings one from anyone of (a) to (c), and (d).

47. The method of claim 46, wherein the method further comprises calculating standard deviations of the absolute device heading of the platform.

48. The method of claims 44 and 46, wherein the continued misalignment of heading between the device and the platform is calculated from the absolute heading of the device and the absolute heading of the platform.

49. The method of claims 45 and 47, wherein the method further comprises calculating standard deviations of the continued misalignment of heading between the device and the platform from the standard deviation of the absolute platform heading and the standard deviation of the absolute device heading.

50. A method for enhancing a navigation solution of a device and a platform, wherein the mobility of the device is constrained or unconstrained within the platform, the method comprising:

detecting and estimating the attitude of the device and the platform, and determining the misalignment between the device and the platform, wherein the device is capable of receiving readings related to navigational information from the platform via a wired or wireless connection.

51. The method of claim 50, wherein the device further comprises a source of absolute position, which may be degraded or denied, and wherein the readings related to navigational information comprise the speed of the platform and one or both of the heading or turning rate of the platform, the method further comprising:

(a) calculating the navigation solution of the platform, the navigation solution including heading of the platform;

(b) calculating the heading of the device from the navigation solution of the device; and

(c) Using the heading of the platform and the heading of the device to calculate the misalignment between the device and the platform.

52. The method of claim 51, wherein the speed of the platform is obtained from an odometer or wheel speed sensors.

53. The method of claim 51, wherein the turning rate of the platform is obtained from a gyroscope on the platform, individual wheel speeds of the platform, or a combination thereof.

54. The method of claim 51, wherein the platform heading is obtained from a magnetometer on the platform, a steering rate sensor on the platform and the speed of the platform, or a combination thereof.

55. The method of claim 50, wherein the platform comprises a positioning system capable of calculating position, velocity and orientation, or a subset thereof, of the platform, wherein the readings related to navigational information comprise the position, velocity and orientation, or a subset thereof, of the platform, wherein the navigation solution of the device is used to determine heading of the device, and wherein the method further comprises utilizing one of:

(a) the platform heading provided from the received orientation of the platform, or

(b) the platform heading derived from the received velocity of the platform,

together with the heading of the device to calculate misalignment between the device and the platform.

56. The method of claim 50, wherein the readings related to navigational information comprises the speed of the platform, wherein the misalignment between the device and the platform is not resolved, and wherein the speed information is used to resolve the misalignment, by using the speed information and assuming candidates of heading misalignment to determine candidate specific forces about the device and comparing the candidate specific forces to specific forces measured by the device.

57. The method of claim 50, wherein the readings related to navigational information comprises the speed of the platform, wherein the misalignment between the device and the platform is resolved, and wherein the speed information is used to resolve pitch and roll of the device, by using the speed information and assuming candidates of pitch and roll to determine candidate specific forces at the device and comparing the candidate specific forces to specific forces measured by the device.

58. The method of claim 50, wherein the readings related to navigational information comprises the speed of the platform, wherein the misalignment of the device and the platform is resolved, and wherein the speed of the platform and the misalignment are utilized to calculate and apply velocity updates for the navigation solution of the device.

59. The method of claim 50, wherein the platform comprises at least one sensor and the readings related to navigational information comprise information from the at least one sensor, wherein the navigation solution of the device is used to determine heading of the device, and wherein the heading of the device and the information from the at least one sensor are utilized to calculate heading of the platform, and to calculate the misalignment between the device and the platform.

60. The method of claim 50, wherein the platform comprises at least one sensor and the readings related to navigational information comprise information from the at least one sensor, wherein the navigation solution of the device is used to determine heading of the device, and wherein the heading of the device and the information from the at least one sensor are utilized to calculate the navigation solution of the platform having heading of the platform, and to calculate the misalignment between the device and the platform.

61. The method of claim 50, wherein the platform comprises at least one sensor and the readings related to navigational information comprise information from the at least one sensor, wherein the navigation solution of the device comprises attitude angles of the device, and wherein the attitude angles of the device and the information from the at least one sensor are utilized to calculate the navigation solution of the platform, wherein the navigation solution of the platform comprises attitude angles of the platform, and calculate the misalignment between the device and the platform.

62. A method for enhancing a navigation solution of a device and a platform, wherein the mobility of the device is constrained or unconstrained within the platform, the method comprising:

detecting and estimating the attitude of the device and the platform, and determining the misalignment between the device and the platform, wherein the device has a means of obtaining velocity information, wherein the misalignment between the device and the platform is resolved, and wherein the device uses the velocity information to resolve the pitch and roll of the device, by using the velocity information and assuming candidates of pitch and roll to determine candidate specific forces at the device and comparing the candidate specific forces to specific forces measured by the device.

63. A method for enhancing a navigation solution of a device and a platform, wherein the mobility of the device is constrained or unconstrained within the platform, the method comprising detecting and estimating the attitude of the device and the platform, and determining the misalignment between the device and the platform, wherein the device has a means of obtaining speed information, wherein the misalignment between the device and the platform is resolved, and wherein the device uses the speed information to resolve the pitch and roll of the device, by using the speed information and assuming candidates of pitch and roll to determine candidate specific forces at the device and comparing the candidate specific forces to specific forces measured by the device.