Error detection for inertial measurement units

• US 8,812,233 B2
• Filed: 12/27/2011
• Issued: 08/19/2014
• Est. Priority Date: 12/27/2011
• Status: Expired due to Fees

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Kontz, Matthew E., Dabbs, Harold Duane
• Primary Examiner(s): Rogers, David A
• Application Number:
  US13/337,414
• Publication Number:
  US 20130160543A1
• Time in Patent Office: 966 Days
• Field of Search: 735/040.3, 735/10, 701/500, 701/502, 701/505, 701/518, 702/104, 702/141
• US Class Current: 701/505
• CPC Class Codes: G01C 19/5776 Signal processing not specific to any of the devices covered by groups G01C19/5607 - G01C19/5719

Abstract

A system for detecting an error in an inertial measurement unit (IMU) is disclosed. The system may have a first IMU including a first plurality of accelerometers and a first rotational rate measurer. The first plurality of accelerometers may be configured to measure acceleration along a plurality of first axes, a first axis of the plurality of first axes being substantially collinear with a collinear axis. The first rotational rate measurer may be configured to measure a first rotational rate about a second axis of the plurality of first axes that is substantially perpendicular to the collinear axis. The system may also have a second IMU and an IMU error detector. The IMU error detector may be configured to receive measurement data from the first IMU and the second IMU; and detect an error based on the measurement data.

Claims

1. A system for detecting an error in an inertial measurement unit comprising:

a first inertial measurement unit including;

a first plurality of accelerometers configured to measure acceleration along a plurality of first axes, a first axis of the plurality of first axes being substantially collinear with a collinear axis; and

a first rotational rate measurer configured to measure a first rotational rate about a second axis of the plurality of first axes that is substantially perpendicular to the collinear axis;

a second inertial measurement unit including;

a second plurality of accelerometers configured to measure acceleration along a plurality of second axes, a first axis of the plurality of second axes being substantially collinear with the collinear axis; and

a second rotational rate measurer configured to measure a second rotational rate about a second axis of the plurality of second axes that is substantially perpendicular to the collinear axis; and

an inertial measurement unit error detector configured to;

receive measurement data from the first inertial measurement unit and the second inertial measurement unit, the measurement data including;

first acceleration data measured along the collinear axis by the first inertial measurement unit,

first rotational rate data corresponding to the first rotational rate

second acceleration data measured along the collinear axis by the second inertial measurement unit, and

second rotational rate data corresponding to the second rotational rate; and

detect a first inertial measurement unit error along the collinear axis based on the first and second acceleration data and the first and second rotational rate data.

2. The system according to claim 1, further including:

a machine, wherein the collinear axis is substantially in a direction of forward movement of the machine.

3. The system according to claim 1, further including:

a machine, wherein the collinear axis is substantially perpendicular to a direction of forward movement of the machine.

4. The system according to claim 1, wherein the second axis of the plurality of first axes is substantially perpendicular to the second axis of the plurality of second axes.

5. The system according to claim 1, further including:

a machine, wherein the first inertial measurement unit and the second inertial measurement unit are mounted on the machine such that an angular variation perpendicular to the collinear axis between the first inertial measurement unit and the second inertial measurement unit is less than or equal to 7.5 degrees.

6. The system according to claim 1, wherein

the measurement data received by the inertial measurement unit error detector further includes:

third and fourth acceleration data measured along the second axis and a third axis, respectively, of the plurality of first axes by the first inertial measurement unit, and

fifth and sixth acceleration data measured along the second axis and a third axis, respectively, of the plurality of second axes by the second inertial measurement unit; and

the inertial measurement unit error detector is further configured to;

detect a second inertial measurement unit error based on the third and sixth acceleration data and the first and second rotational rate data, and

detect a third inertial measurement unit error based on the fourth and fifth acceleration data and the first and second rotational rate data.

7. The system according to claim 1, wherein the inertial measurement unit does not require data from any other inertial measurement unit or sensor in order to detect the first inertial measurement unit error.

8. A method for detecting an error in an inertial measurement unit comprising:

receiving first measurement data from a first inertial measurement unit, the measurement data including first acceleration data in first, second, and third directions and first rotational rate data;

receiving second measurement data from a second inertial measurement unit that is separated by a distance from the first inertial measurement unit, the second measurement data including second acceleration data in the first, second, and third directions and a second rotational rate data;

determining whether an error has occurred in the first or second inertial measurement units using the first and second acceleration data, the first and second rotational rate data, and the distance between the first inertial measurement unit and the second inertial measurement unit.

9. The method according to claim 8, wherein determining whether the error has occurred does not use data from any inertial measurement units or sensors other than the first and second inertial measurement units.

10. The method according to claim 8, determining whether the error has occurred including:

calculating a cross check value for each of the first, second, and third directions based on the first and second acceleration data, the first and second rotational rate data, and the distance between the first inertial measurement unit and the second inertial measurement unit;

comparing the cross check value for each of the first, second, and third directions to a first, second, and third threshold value, respectively; and

determining that the error may have occurred if the cross check value for any of the first, second, or third directions exceeds the first, second, or third threshold value, respectively.

11. The method according to claim 10, the determining step further including:

debouncing a state value for a debounce time period when it is determined that the error may have occurred; and

determining that the error has occurred if the cross check value for any of the first, second, or third directions exceeds the first, second, or third threshold value, respectively, after the debounce time period.

12. The method according to claim 10, wherein the cross check value for the first, second, and third directions are calculated according to the following equations, respectively:

13. The method according to claim 10, wherein the cross check value for the first, second, and third directions are calculated according to the following equations, respectively:

14. A system for detecting an error in an inertial measurement unit comprising:

a first inertial measurement unit that generates first acceleration data in first, second, and third directions and first rotational rate data;

a second inertial measurement unit that is separated by a distance from the first inertial measurement unit and that generates second acceleration data in the first, second and third directions and second rotational rate data; and

an error detector configured to;

receive the first acceleration data and the first rotational rate data from the first inertial measurement unit and the second acceleration data and the second rotational rate data from the second inertial measurement unit; and

determine whether an error has occurred using the first and second acceleration data, the first and second rotational rate data, and the distance between the first inertial measurement unit and the second inertial measurement unit.

15. The system according to claim 14, the error detector being further configured to determine whether the error has occurred without using data from any inertial measurement units or sensors other than the first and second inertial measurement units.

16. The system according to claim 14, the error detector being further configured to:

calculate a cross check value for each of the first, second, and third directions based on the first and second acceleration data, the first and second rotational rate data, and the distance between the first inertial measurement unit and the second inertial measurement unit;

compare the cross check value for each of the first, second, and third directions to a first, second, and third threshold value, respectively; and

determine that an error may have occurred if the cross check value for any of the first, second, or third directions exceeds the first, second, or third threshold value, respectively.

17. The system according to claim 16, the error detector being further configured to:

debounce a state value for a debounce time period when it is determined that the error may have occurred; and

determine that an error has occurred if the cross check value for any of the first, second, or third directions exceeds the first, second, or third threshold value, respectively, after the debounce time period.

18. The system according to claim 16, the error detector being further configured to calculate the cross check value for the first, second, and third directions according to the following equations, respectively:

19. The system according to claim 16, the error detector being further configured to calculate the cross check value for the first, second, and third directions according to the following equations, respectively: