Method, apparatus and computer program for azimuth determination e.g. for autonomous navigation applications

• US 20060195254A1
• Filed: 02/28/2005
• Published: 08/31/2006
• Est. Priority Date: 02/28/2005
• Status: Active Grant

• Current Assignee: Vectronix AG (Safran SA)
• Original Assignee: Vectronix AG (Safran SA)
• Inventors: Ladetto, Quentin, Vanderstraeten, Celine
• Granted Patent: US 7,421,340 B2
• Time in Patent Office: Days
• US Class Current: 701/207
• CPC Class Codes: G01C 17/00 Compasses; Devices for ascertaining true or magnetic north for navigation or surveying purposes using gyroscopic effect G01C19/00
• CPC Class Codes: G01C 17/38 Testing, calibrating, or compensating of compasses
• CPC Class Codes: G01C 21/1654 with electromagnetic compass
• CPC Class Codes: G01C 21/20 Instruments for performing navigational calculations G01C21/24, G01C21/26 take precedence

Abstract

For an observer equipped with a first azimuth data source responsive to a magnetic field to deliver first azimuth data, such as a compass, and with a second azimuth data source delivering second azimuth data and which is independent of magnetic fields, such as a gyroscope. The azimuth is determined by: analyzing the first and second azimuth data to determine whether a magnetic disturbance is present, and determining azimuth selectively on the basis of: the first azimuth data, the second azimuth data, or a combination of the first and second azimuth data, as a function of the result of the comparing step. In an embodiment, the choices of azimuth data source and events such as magnetic disturbances, sensor updates, types of trajectory deduced, are stored as a history sequence over successive time windows, by analogy with a DNA sequence, and is exploited for optimizing azimuth or navigation results.

Claims

1. A method of determining an azimuth using a first azimuth data source responsive to a magnetic field to deliver first azimuth data, and a second azimuth data source delivering, independently of magnetic field, second azimuth data, comprising the steps of:

analyzing said first and second azimuth data to determine whether a magnetic disturbance is present, and

determining said azimuth selectively on the basis of;

said first azimuth data, said second azimuth data, or a combination of said first and second azimuth data, as a function of the result of said analyzing step.

2. Method according to claim 1, wherein said analyzing step comprises the sub-steps of:

acquiring said first and second azimuth data,

comparing said first and second azimuth data, and

identifying a magnetic field disturbance on the basis of said comparison, and

wherein said azimuth determining step comprises basing the determined azimuth, in a situation in which a magnetic disturbance is determined to be present, on one of;

i) said second azimuth data, without reference to the first azimuth data, or

ii) a combination of said second azimuth data and said first azimuth data.

3. Method according to claim 1, wherein said analyzing step comprises the sub-steps of:

acquiring said first and second azimuth data over a plurality of sampling periods within a time window,

performing a statistical analysis on said first and second azimuth data for said sampling periods, and

identifying a magnetic field disturbance on the basis of said statistical analysis, and wherein said azimuth determining step comprises basing the determined azimuth, in a situation in which a magnetic disturbance is determined to be present, on one of;

i) said second azimuth data, without reference to the first azimuth data, or

ii) a combination of said second azimuth data and said first azimuth data.

4. Method according to claim 1, wherein said analyzing step comprises the sub-steps of:

acquiring said first and second azimuth data over a plurality of sampling periods within a time window,

determining the normal standard deviation of said first azimuth data and the normal standard deviation of said second azimuth data for said sampling periods,

determining the ratio of said normal standard deviation of said first azimuth data to said normal standard deviation of said second azimuth data for said sampling periods,

comparing said ratio to a determined threshold value, and

identifying a magnetic field disturbance in a situation in which said ratio crosses said determined threshold,

wherein said azimuth determining step comprises basing the determined azimuth, in a situation in which a magnetic disturbance is determined to be present, on one of;

i) said second azimuth data, without reference to the first azimuth data, or

ii) a combination of said second azimuth data and said first azimuth data.

5. Method according to claim 1, further comprising the step of determining a change of azimuth on the basis of said second azimuth data.

6. Method according to claim 1, wherein said analyzing step comprises the sub-steps of:

acquiring said first and second azimuth data over a plurality of sampling periods within a determined time window, for a succession of time windows,

performing an analysis on first and second azimuth data for said sampling periods of at least a current time window and its preceding time window,

taking at least one of the following actions on the basis of said analysis;

i) using only said first azimuth data of a current window to determine said azimuth,

ii) using only said second azimuth data of a current window to determine said azimuth,

iii) using a combination of said first azimuth data and said second azimuth of a current time window to determine said azimuth,

iv) identifying a type path currently followed, and

v) updating at least one parameter of said second azimuth data source.

7. Method according to claim 1, wherein said analyzing step comprises the sub-steps of:

acquiring said first and second azimuth data for a succession of time windows,

for at least some time windows of said succession, recording events occurring within a said time window, to obtain a sequence history of azimuth events over successive time windows, and

using said sequence history as input to optimize the determination of said azimuth and/or a determination of a position and/or a trajectory.

8. Method according to claim 1, wherein said analyzing step comprises the sub-steps of:

acquiring said first and second azimuth data for a succession of time windows,

for at least some time windows of said succession, recording events occurring within a said time window, said events comprising at least one of;

i) choice of source(s) of azimuth data used for determining azimuth data,

ii) sensor update or recalibration,

iii) identified trajectory type,

iv) presence of a magnetic field disturbance,

to obtain a sequence history of azimuth events over successive time windows, and

using said sequence history as input to optimize the determination of said azimuth and/or a determination of a position and/or a trajectory.

9. Method according to claim 1, wherein said analyzing step comprises acquiring said first and second azimuth data over a plurality of sampling periods within a determined time window, and performing said acquisition for a succession of time windows.

10. Method according to claim 1, wherein said analyzing step further comprises the steps of:

acquiring said first and second azimuth data over a plurality of sampling periods within a time window,

analyzing said first and second azimuth data of that time window,

on the basis of said analysis, performing at least one of;

i) updating or recomputing at least one azimuth data of said time window, and

ii) updating or recomputing a present real-time azimuth.

11. Method according to claim 1, wherein said analyzing step comprises the sub-steps of:

acquiring said first and second azimuth data over a plurality of sampling periods within a time window,

determining a position on the basis of said data,

analyzing said first and second azimuth data of that time window,

on the basis of said analyzing step, performing at least one of;

i) recomputing at least one determined position in said time window, and

ii) updating or recomputing a present real-time position.

12. Method according to claim 1, comprising the steps of:

determining, on the basis of said analyzing step, a first condition in which no substantial magnetic field is present,

enabling an update of said second azimuth data source, on the basis of said first azimuth data from said first azimuth data source, only if said first condition is satisfied.

13. Method according to claim 1, further comprising the steps of:

determining a current trajectory in terms of an amount of change in azimuth,

using said determined current trajectory as a parameter for commanding a management of said first and/or second azimuth data source(s) and/or as a parameter for said analyzing step and/or said determining step.

14. Method according to claim 1, further comprising the steps of:

determining a current trajectory in terms of an amount of change in azimuth,

identifying a current trajectory following a specific change of direction, notably a 90°

or 180°

change of direction,

using said identified specific change of direction as a parameter for commanding a management of said first and/or second azimuth data source(s) and/or as a parameter for said analyzing step and/or said determining step.

15. Method according to claim 1, further comprising the steps of:

determining a current trajectory in terms of an amount of change in azimuth,

identifying a current trajectory following a substantially straight line direction, corresponding to substantially no change in azimuth

using said identified substantially straight line direction as a parameter for commanding a management of said first and/or second azimuth data source(s) and/or as a parameter for said analyzing step and/or said determining step.

16. Method according to claim 1, further comprising the steps of:

performing said azimuth determination over at least two successive determined time windows,

for each successive time window, determining whether a trajectory follows a substantially straight line direction,

determining whether a trajectory for a current time window and for a previous time window both follow a substantially straight line direction,

in the affirmative, using trajectory data of said previous window and said current window to establish a continuity relation in which said trajectory is considered to follow a same substantially straight line.

17. Method according to claim 1, wherein said first azimuth data source comprises at least one magnetic compass.

18. Method according to claim 1, wherein said second azimuth data source comprises at least one gyroscope.

19. Method according to claim 1, wherein said second azimuth data source comprises an azimuth data source that is subject to drift error over time and is updatable with at least one operating parameter value.

20. Method according to claim 1, wherein said second azimuth data source comprises at least one gyroscope, said gyroscope being updatable with at least one of:

a gyroscope scale factor,

a gyroscope azimuth reference,

a gyroscope bias.

21. Method according to claim 1, further comprising the step of using said determined azimuth as a source of azimuth data for autonomous navigation.

22. Method according to claim 1, wherein said first and second azimuth data sources are carried by a human pedestrian.

23. Method according to claim 1, wherein at least one of said first and second azimuth data sources is mounted substantially at a waist position or at the upper part of the body, or a trunk portion of the body of a pedestrian.

24. Method according to claim 1, wherein said first and second azimuth data sources are aboard a vehicle.

25. Method according to claim 1, further comprising the steps of:

producing a history sequence of past events up to a current time, said history sequence expressing at least a magnetic field characteristic determined over a respective time window, said magnetic field characteristic being classed as one of;

i) a magnetically stable environment,

ii) a magnetically disturbed environment,

iii) a potentially magnetically disturbed environment, and

wherein said azimuth determining step comprises using at least one said determined magnetic field characteristic as a parameter to determine said azimuth.

26. Method according to claim 1, further comprising the steps of:

producing a history sequence of past events up to a current time, said history sequence expressing at least an azimuth or trajectory characteristic determined over a respective time window, said azimuth or trajectory characteristic being classed as one of;

i) a displacement substantially along a straight line,

ii) a displacement along a curve with a significant substantial continuous change in azimuth,

iii) a general situation not corresponding to listed situations i) or ii), and

wherein said determining step comprises using at least one said determined azimuth or trajectory characteristic as a parameter to determine said azimuth.

27. Method according to claim 1, performed in real time to produce a substantially real-time azimuth determination.

59. A computer-readable medium including computer-executable instructions for performing the method recited in claim 1.

28. A method of autonomous navigation comprising the steps of:

providing a first azimuth data source responsive to a magnetic field to deliver first azimuth data,

providing a second azimuth data source whose output is substantially uninfluenced by magnetic fields to deliver second azimuth data,

analyzing said first and second azimuth data to determine whether a magnetic disturbance is present,

producing an azimuth determination on the basis of said analyzing step; and

producing navigation information on the basis of said azimuth determination.

29. Method of determining an azimuth in a navigation application, comprising the steps of:

acquiring first azimuth data from magnetic compass means,

acquiring second azimuth data from gyroscope means,

using said first and second azimuth data to detect a presence of a magnetic disturbance,

in a situation in which a magnetic disturbance is detected, determining said azimuth from one of;

i) a combination said first and second azimuth data, or

ii) said second azimuth alone, and

calibrating or updating an azimuth reference and/or a bias and/or a scale factor of said gyroscope means using said first azimuth data in a situation in which substantially no magnetic disturbance is detected.

30. An apparatus for determining an azimuth, said apparatus comprising:

a first azimuth data source responsive to a magnetic field to deliver first azimuth data,

a second azimuth data source delivering, independently of magnetic field, second azimuth data,

means for analyzing said first and second azimuth data to determine whether a magnetic disturbance is present, and

means for determining said azimuth selectively on the basis of;

said first azimuth data, said second azimuth data, or a combination of said first and second azimuth data as a function of a result of an analysis by said analyzing means.

31. Apparatus according to claim 30, wherein said analyzing means comprises:

means for acquiring said first and second azimuth data,

means for comparing said first and second azimuth data, and

means for identifying a magnetic field disturbance on the basis of said comparison, and wherein

said azimuth determining means comprises means for basing the determined azimuth, in a situation in which a magnetic disturbance is determined to be present, on one of;

i) said second azimuth data, without reference to the first azimuth data, or

ii) a combination of said second azimuth data and said first azimuth data.

32. Apparatus according to claim 30, wherein said analyzing means comprises:

means for acquiring said first and second azimuth data over a plurality of sampling periods within a time window,

means for performing a statistical analysis on said first and second azimuth data for said sampling periods, and

means for identifying a magnetic field disturbance on the basis of said statistical analysis, and wherein

said azimuth determining means comprises means for basing the determined azimuth, in a situation in which a magnetic disturbance is determined to be present, on one of;

i) said second azimuth data, without reference to the first azimuth data, or

ii) a combination of said second azimuth data and said first azimuth data.

33. Apparatus according to claim 30, wherein said analyzing means comprises:

means for acquiring said first and second azimuth data over a plurality of sampling windows within a time window,

means for determining the normal standard deviation of said first azimuth data and the normal standard deviation of said second azimuth data for said sampling periods,

means for determining the ratio of said normal standard deviation of said first azimuth data to the normal standard deviation of said second azimuth data for said sampling periods,

means for comparing said ratio to a determined threshold value, and

means for identifying a magnetic field disturbance in a situation in which said ratio crosses said determined threshold, and

wherein said azimuth determining means comprises means for basing the determined azimuth, in a situation in which a magnetic disturbance is determined to be present, on one of;

i) said second azimuth data, without reference to the first azimuth data, or

ii) a combination of said second azimuth data and said first azimuth data.

34. Apparatus according to claim 30, further comprising means for determining a change of azimuth of on the basis of said second azimuth data.

35. Apparatus according to claim 30, where said analyzing means comprises:

means for acquiring said first and second azimuth data over a plurality of sampling periods within a determined time window, and for performing said acquisition for a succession of time windows,

means for performing an analysis on first and second azimuth data for said sampling periods of at least a current time window and its preceding time window,

means for taking at least one of the following actions on the basis of said analysis;

i) using only said first azimuth data of a current window to determine said azimuth,

ii) using only said second azimuth data of a current window to determine said azimuth,

iii) using a combination of said first azimuth data and said second azimuth of a current time window to determine said azimuth,

iv) identifying a type path currently followed, and

v) updating at least one parameter of said second azimuth data source.

36. Apparatus according to claim 30, wherein said analyzing means comprises:

means for acquiring said first and second azimuth data for a succession of time windows,

means for recording events occurring within a said time window, for at least some time windows of said succession, to obtain a sequence history of azimuth events over successive time windows, and

means for receiving said sequence history as input to optimize a determination of said azimuth and/or a determination of a position and/or a trajectory.

37. Apparatus according to claim 30, wherein said analyzing means comprises:

means for acquiring said first and second azimuth data for a succession of time windows,

means for recording events occurring within a said time window, for at least some time windows of said succession, said events comprising at least one of;

i) choice of source(s) of azimuth data used for determining azimuth data,

ii) sensor update or recalibration,

iii) identified trajectory type,

iv) presence of a magnetic field disturbance,

to obtain a sequence history of azimuth events over successive time windows, and

means for receiving said sequence history as input to optimize a determination of said azimuth and/or a determination of a position and/or a trajectory.

38. Method according to claim 30, wherein said analyzing means comprises means for acquiring first and second azimuth data samples at successive time intervals within a determined time window, and for performing said acquisition for a succession of time windows.

39. Apparatus according to claim 30, wherein said analyzing means further comprises:

means for acquiring said first and second azimuth data over a plurality of sampling periods within a time window,

means for analyzing said first and second azimuth data of that time window, and

means, cooperating with said analyzing means, for performing at least one of;

i) updating or recomputing at least one azimuth data of said time window, and

ii) updating or recomputing a present real-time azimuth.

40. Apparatus according to claim 30, wherein said analyzing means further comprises:

means for acquiring said first and second azimuth data over a plurality of sampling periods within a time window,

means for determining a position on the basis of said data,

means for analyzing said first and second azimuth data of that time window,

means, cooperating with said analyzing means, for performing at least one of;

i) recomputing at least one said determined position in said time window, and

ii) updating or recomputing a present real-time position.

41. Apparatus according to claim 30, comprising:

means for determining, on the basis of analysis data from said analyzing means, a first condition in which no substantial magnetic disturbance is present, and

means for enabling an update of said second azimuth data source, on the basis of said first azimuth data from said first azimuth data source, only if said first condition is satisfied.

42. Apparatus according to claim 30, further comprising:

means for determining a current trajectory in terms of an amount of change in azimuth,

means for commanding a management of said first and/or second azimuth data source(s) and/or said analyzing means and/or said determining means on the basis of said determined current trajectory as a parameter for determining an azimuth.

43. Apparatus according to claim 30, further comprising:

means for determining a current trajectory in terms of an amount of change in azimuth,

means for identifying a current trajectory following a specific change of direction, notably a 90°

or 180°

change of direction,

means for commanding a management of said first and/or second azimuth data source(s) and/or said analyzing means and/or said determining means on the basis of said specific change of direction.

44. Apparatus according to claim 30, further comprising:

means for determining a current trajectory in terms of an amount of change in azimuth,

means for identifying a current trajectory following a substantially straight line direction, corresponding to substantially no change in azimuth,

means for commanding a management of said first and/or second azimuth data source(s) and/or said analyzing means and/or said determining means on the basis of said identified substantially straight line direction.

45. Apparatus according to claim 30, further comprising:

means for performing said azimuth determination over at least two successive determined time windows,

means, operative for each successive time window, for determining whether a trajectory follows a substantially straight line direction,

means for determining whether a trajectory for a current time window and for a previous time window both follow a substantially straight line direction, and, in the affirmative, operative for using trajectory data of said previous window and said current window to establish a continuity relation in which said trajectory is considered to follow a same substantially straight line.

46. Apparatus according to claim 30, wherein said first azimuth data source comprises at least one magnetic compass.

47. Apparatus according to claim 30, wherein said second azimuth data source comprises at least one gyroscope.

48. Apparatus according to claim 30, wherein said second azimuth data source comprises an azimuth data source that is subject to drift error over time and is updatable with at least one operating parameter value.

49. Apparatus according to claim 30, wherein said second azimuth data source comprises at least one gyroscope, said gyroscope being updatable with at least one of:

a gyroscope scale factor,

a gyroscope azimuth reference,

a gyroscope bias.

50. Apparatus according to claim 30, further comprising autonomous navigation means operatively connected to said azimuth determination means produce navigation data.

51. Apparatus according to claim 30, provided with means for fitting on a human pedestrian.

52. Apparatus according to claim 30, provided with means for fitting on a human pedestrian, with at least one of said first and second azimuth data sources mounted substantially at a waist position or at the upper part of the body, or a trunk portion of the body of said pedestrian.

53. Apparatus according to claim 30, provided with means for fitting in a vehicle.

54. Apparatus according to claim 30, further comprising:

means for producing a history sequence of past events up to a current time, said history sequence expressing at least a magnetic field characteristic determined over a respective time window, said magnetic field characteristic being classed as one of;

i) a magnetically stable environment,

ii) a magnetically disturbed environment,

iii) a potentially magnetically disturbed environment, and

wherein said azimuth determining means comprises means using at least one said determined magnetic field characteristic as a parameter to determine said azimuth.

55. Apparatus according to claim 30, further comprising:

means for producing a history sequence of past events up to a current time, said history sequence expressing at least an azimuth or trajectory characteristic determined over a respective time window, said azimuth or trajectory characteristic being classed as one of;

i) a displacement substantially along a straight line,

ii) a displacement along a curve with a significant substantial continuous change in azimuth,

iii) a general situation not corresponding to listed situations i) or ii), and

wherein said determining means comprises using at least one said determined azimuth or trajectory characteristic as a parameter to determine said azimuth.

56. Apparatus according to claim 30, wherein said analyzing means and determining means are operative to provide a substantially real-time azimuth determination.

57. An autonomous navigation apparatus comprising:

a first azimuth data source responsive to a magnetic field to deliver first azimuth data,

a second azimuth data source, whose output is substantially uninfluenced by magnetic fields, delivering second azimuth data,

means for analyzing said first and second azimuth data to determine whether a magnetic disturbance is present,

means for producing an azimuth determination on the basis of said analyzing means; and

means for delivering navigation information on the basis of said azimuth determination.

58. An apparatus for determining an azimuth in a navigation application, comprising:

means for acquiring first azimuth data from magnetic compass means,

means for acquiring second azimuth data from gyroscope means,

means for using said first and second azimuth data to detect a presence of a magnetic disturbance,

means, operative in a situation in which a magnetic disturbance is detected, for determining said azimuth from one of;

i) a combination said first and second azimuth data, or

ii) said second azimuth alone, and

means for calibrating or updating an azimuth reference and/or a bias and/or a scale factor of said gyroscope means using said first azimuth data in a situation in which substantially no magnetic disturbance is detected.