HEADING CONFIDENCE INTERVAL ESTIMATION

• US 20140278183A1
• Filed: 08/23/2013
• Published: 09/18/2014
• Est. Priority Date: 03/13/2013
• Status: Active Grant

• Current Assignee: Invensense Incorporated (TDK Corporation)
• Original Assignee: Invensense Incorporated (TDK Corporation)
• Inventors: Zheng, Yuan, Lin, Shang-Hung, Keal, Kerry
• Granted Patent: US 10,132,829 B2
• Time in Patent Office: Days
• US Class Current: 702/96
• 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 25/005 initial alignment, calibration or starting-up of inertial devices
• CPC Class Codes: G01P 15/00 Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
• CPC Class Codes: G01P 21/00 Testing or calibrating of apparatus or devices covered by the preceding groups

Abstract

An inertial measurement system is disclosed. The inertial measurement system has an accelerometer processing unit that generates a calibrated accelerometer data. The inertial measurement system further includes a magnetometer processing unit generates a calibrated magnetometer data, and a gyroscope processing unit generates a calibrated gyroscope data. Using the calibrated accelerometer data, the calibrated magnetometer data, and the calibrated gyroscope data, the inertial measurement system generates a heading angle error indicative of the accuracy of the heading angle error.

Claims

1. An inertial measurement system comprising:

an accelerometer processing unit operable to generate a calibrated accelerometer data;

a magnetometer processing unit operable to generate a calibrated magnetometer data; and

a gyroscope processing unit operable to generate a calibrated gyroscope data, wherein the inertial measurement system is operable to generate an orientation angle indicative of the accuracy of the orientation angle using the calibrated accelerometer data, the calibrated magnetometer data, and the calibrated gyroscope data.

2. The inertial measurement system of claim 1, wherein the accuracy of the orientation angle is a measure of the correctness of the orientation angle over an interval of time.

3. The inertial measurement system of claim 1, wherein the inertial measurement system is operable to generate a confidence interval of the orientation.

4. The inertial measurement system of claim 3, wherein the confidence interval is indicative of the accuracy of the orientation angle.

5. The inertial measurement system of claim 3, wherein the confidence interval is related to a statistical property of the inner product of an accelerometer vector and a magnetometer vector, the accelerometer vector being a vector related to the calibrated accelerometer data and the magnetometer vector being a vector related to the calibrated magnetometer data.

6. The inertial measurement system of claim 1, wherein the accelerometer processing unit includes an accelerometer calibration and gravity extraction block responsive to an accelerometer data and an inverse quaternion signal and operable to generate the calibrated accelerometer data in world coordinates.

7. The inertial measurement system of claim 6, wherein the accelerometer processing unit further includes a first comparator operable to compare the calibrated accelerometer data to a predefined reference in world coordinates to generate a first comparison output.

8. The inertial measurement system of claim 7, wherein the magnetometer processing unit includes a magnetometer calibration and anomaly rejection block responsive to a magnetometer data and the inverse quaternion signal and operable to generate the calibrated magnetometer data in world coordinates.

9. The inertial measurement system of claim 8 wherein the magnetometer processing unit further includes a second comparator operable to compare the calibrated magnetometer data to the predefined reference in world coordinates and to generate a second comparison output.

10. The inertial measurement system of claim 9, wherein the gyroscope processing unit includes a gyroscope calibration block responsive to a gyroscope data and operable to generate the calibrated gyroscope data.

11. The inertial measurement system of claim 10, wherein the gyroscope processing unit further includes a gyroscope integration block operable to integrate the calibrated gyroscope data and generate a gyroscope quaternion data.

12. The inertial measurement system of claim 11, further including a sensor fusion block responsive to the summation of the first and the second comparison outputs and the gyroscope quaternion data, the sensor fusion block operable to generate a quaternion output representative of the orientation.

13. The inertial measurement system of claim 12, further including a converter responsive to the summation of the first and the second comparison outputs and generate the confidence interval.

14. The inertial measurement system of claim 16, further including an inverse block responsive to the quaternion output and operable to generate the inverse quaternion signal.

15. The inertial measurement system of claim 14, further including a transform block responsive to the quaternion output to generate orientation.

16. The inertial measurement system of claim 1, further including an accelerometer, a magnetometer, and a gyroscope, wherein the accelerometer, the magnetometer, and the gyroscope reside on one semiconductor chip and a calibration and gravity extraction block, a magnetometer calibration and anomaly rejection block, a gyroscope calibration block, a gyroscope integration block, a sensor fusion, comparators, an inverse block, and a converter reside on another semiconductor chip.

17. The inertial measurement system of claim 1, further including an accelerometer, a magnetometer, and a gyroscope, wherein the accelerometer, the magnetometer, the gyroscope, the accelerometer processing unit, the magnetometer processing unit, the gyroscope processing unit, a sensor fusion, comparators, an inverse block, and a converter reside on the same semiconductor chip.

18. The inertial measurement system of claim 8, wherein the inertial measurement system uses the accelerometer data as a reference to a gravity direction and the magnetometer data as a reference to a magnetic north direction.

19. The inertial measurement system of claim 7, wherein the calibration and gravity extraction unit and the first comparator are implemented in hardware or software.

20. The inertial measurement system of claim 7, wherein the magnetometer calibration and anomaly rejection block and the first comparator are implemented in hardware or software.

21. The inertial measurement system of claim 1, wherein a gyroscope calibration block and a gyroscope integration block are implemented in hardware or software.

22. An inertial measurement system comprising:

an accelerometer processing unit operable to generate a calibrated accelerometer data;

a magnetometer processing unit operable to generate a calibrated magnetometer data;

a gyroscope processing unit operable to generate a calibrated gyroscope data,

wherein the inertial measurement system is operable to generate an angle error, the accuracy of which is measured using a confidence interval relating to the calibrated accelerometer data and the calibrated magnetometer data.

23. A method of estimating heading using an inertial measurement system comprising:

calibrating an accelerometer data to generate a calibrated accelerometer data with an accelerometer calibration and gravity extraction block;

calibrating a magnetometer data to generate a calibrated magnetometer data with a magnetometer calibration and anomaly rejection block;

calibrating a gyroscope data to generate a gyroscope data with a gyroscope calibration block; and

using the calibrated accelerometer data, the calibrated magnetometer data, and the calibrated gyroscope data, generating an angle error, the angle error being a measure indicative of the accuracy of the orientation angle.

24. The method of estimating a heading, as recited in claim 23, wherein the measure is a confidence interval value.

25. The method of estimating heading, as recited in claim 23, further including comparing the calibrated accelerometer data to a predefined reference in world coordinates to generate a first comparison output.

26. The method of estimating heading, as recited in claim 23, further including comparing the calibrated magnetometer data to the predefined reference in world coordinates to generate a second comparison output.

27. The method of estimating heading, as recited in claim 26, wherein calibrated gyroscope data is integrated.

28. The method of estimating heading, as recited in claim 27, further including generating an estimate of the angle and an error boundary using a summation of the first and the second comparison outputs.

29. A method of generating an angle error comprising:

determining whether or not a magnetic anomaly is detected;

if a magnetic anomaly is not detected, calculating an orientation error boundary with tilt and heading compensation from a calibrated accelerometer data, a calibrated magnetometer data, and a calibrated gyroscope data; and

if a magnetic anomaly is detected, calculating an orientation error boundary using gyroscope data.