Methods of attitude and misalignment estimation for constraint free portable navigation

• US 10,203,207 B2
• Filed: 03/22/2012
• Issued: 02/12/2019
• Est. Priority Date: 03/23/2011
• Status: Active Grant

• Current Assignee: Trusted Positioning Inc. (TDK Corporation)
• Original Assignee: Invensense Incorporated (TDK Corporation)
• Inventors: Georgy, Jacques, Syed, Zainab, Goodall, Christopher, Atia, Mohamed, Noureldin, Aboelmagd, El-Sheimy, Naser
• Primary Examiner(s): Smith, Jelani A
• Assistant Examiner(s): Alsomiri, Majdi
• Application Number:
  US13/426,884
• Publication Number:
  US 20120245839A1
• Time in Patent Office: 2,518 Days
• Field of Search: 701408, 702150
• 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 estimating heading misalignment between a device and a platform, wherein the mobility of the device is constrained or unconstrained within the platform, wherein the device has motion sensors and wherein a source of absolute velocity is available, the method comprising:

a) obtaining motion sensors readings;

b) obtaining absolute velocity;

c) choosing multiple possible candidates of heading misalignment to cover a range of angular value ambiguity for the heading misalignment between the device and the platform, wherein the heading misalignment between the device and the platform is a difference between a heading of the device and a heading of the platform and wherein the heading of the device is a heading of a frame of the motion sensors within the device;

d) estimating motion sensor readings for each chosen candidate of heading misalignment based at least in part on the obtained absolute velocity;

e) performing at least one of;

i) transforming the estimated motion sensor readings from a frame of the absolute velocity to the motion sensor frame and comparing the transformed estimated motion sensor readings for each chosen candidate of heading misalignment to the obtained motion sensor readings in the motion sensor frame; and

ii) transforming the obtained motion sensor readings from the motion sensor frame to a frame of the absolute velocity and comparing the estimated motion sensor readings for each chosen candidate of heading misalignment to the transformed obtained motion sensor readings in the frame of the absolute velocity; and

f) assess each chosen candidate of heading misalignment based on the comparison.

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

3. The method of claim 1, wherein the device comprises at least three accelerometers and wherein said accelerometers have quality specifications, further comprising:

detecting and estimating an attitude of the device and the platform, and determining a misalignment between the device and the platform, by calculating roll and pitch of the device using specific forces measured at the device, and calculating a 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 1, further comprising:

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

5. The method of claim 1, wherein assessing each chosen candidate of heading misalignment comprises:

a) measuring specific forces at the device using the motion sensors;

b) determining specific forces at the device for each candidate of heading misalignment; and

c) comparing the candidate specific forces to the measured specific forces.

6. The method of claim 5, wherein candidates of heading of the device are calculated from each candidate of heading misalignment between the device and the platform and a platform heading.

7. The method of claim 6, wherein the platform heading is determined from the source of absolute velocity.

8. The method of claim 7, wherein the candidate specific forces at the device are determined using a time rate of change of the absolute velocity, acceleration of gravity, a pitch and roll of the device, and the candidates of heading of the device.

9. The method of claim 5, wherein comparing the candidate specific forces to the measured specific forces is utilized to select one of the candidates of heading misalignment as the estimated heading misalignment between the device and the platform.

10. The method of claim 5, wherein comparing the candidate specific forces to the measured specific forces is utilized to select one of the candidates of heading misalignment as the estimated heading misalignment between the device and the platform through an iterative process.

11. The method of claim 1, wherein the device comprises at least three accelerometers, further comprising:

detecting and estimating an attitude of the device and the platform, and determining a 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.

12. The method of claim 1, further comprising:

detecting and estimating an attitude of the device and the platform, and determining a 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.

13. The method of claim 1, further comprising:

detecting and estimating an attitude of the device and the platform, and determining a 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.

14. The method of claim 1, further comprising:

detecting and estimating an attitude of the device and the platform, and determining a 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.

15. The method of claim 1, further comprising:

detecting and estimating an attitude of the device and the platform, and determining a 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.

16. The method of claim 1, wherein the estimated heading misalignment between the device and the platform is used to enhance a navigation solution.

17. The method of claim 1, wherein the source of absolute velocity is a global navigation satellite system (GNSS).

18. The method of claim 1, wherein the source of absolute velocity is a magnetometer.

19. The method of claim 1, wherein the source of absolute velocity is derived from wireless signals of a wireless communication system.

20. The method of claim 1, wherein the source of absolute velocity is available for a short period of time.

21. The method of claim 1, further comprising calculating a standard deviation of the estimated heading misalignment between the device and the platform.

22. The method of claim 1, further comprising calculating a device heading from the estimated heading misalignment between the device and the platform and a platform heading.

23. The method of claim 22, wherein the platform heading is determined from the source of absolute velocity.

24. The method of claim 1, wherein the estimated heading misalignment between the device and the platform is an initial heading misalignment.

25. The method of claim 24, further comprising calculating an initial device heading from the estimated initial heading misalignment between the device and the platform and an initial platform heading.

26. The method of claim 25, wherein the initial platform heading is determined from the source of absolute velocity.

27. The method of claim 24, further comprising calculating a standard deviation of the estimated initial heading misalignment between the device and the platform.

28. The method of claim 24, wherein the estimated initial heading misalignment between the device and the platform is used to enhance a navigation solution.