Method for calibrating an inertial measurement unit

• US 20040211238A1
• Filed: 05/24/2004
• Published: 10/28/2004
• Est. Priority Date: 11/06/2001
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Hanse, Joel G.
• Granted Patent: US 6,968,281 B2
• Time in Patent Office: Days
• US Class Current: 73/1.38
• CPC Class Codes: G01C 25/005 initial alignment, calibration or starting-up of inertial devices
• CPC Class Codes: G01P 21/00 Testing or calibrating of apparatus or devices covered by the preceding groups

Abstract

A method for testing inertial measurement devices on a multi-axis rate table without having to utilize slip rings to transfer signals between the inertial measurement devices and remote processors by incorporating a processor internal to the inertial measurement devices and transferring the signals directly to the processors for determining and storing the calibration coefficients of the inertial measurement devices internally so that they are self calibrating.

Claims

1. In a system that includes an inertial measurement unit having an internal memory device and an internal processor, a prep-station having test and calibration software, and a rate table that subjects the inertial measurement unit to a known plurality of motion and environmental conditions, a method of using the inertial measurement unit comprising:

loading the inertial measurement unit on the prep-station;

loading the processor, via the prep-station, with the test and calibration software and values of the known motion and environmental conditions;

placing the inertial measurement unit on the rate table;

subjecting the inertial measurement unit, during a test, to the known plurality of motion and environmental conditions while the inertial measurement unit is on the rate table; and

executing the test software, at the processor, during the test to read outputs of the inertial measurement unit, determine errors, and calculate correction coefficients, wherein the outputs of the inertial measurement unit are sent to the processor via a path that does not include slip rings.

2. The method of claim 1, further comprising storing the correction coefficients in the internal memory device.

3. The method of claim 2, wherein storing the correction coefficients occurs during the test.

4. The method of claim 2, further comprising executing the calibration software, at the processor after the test, to compensate outputs of the inertial measurement unit with the stored correction coefficients.

5. The method of claim 1, wherein subjecting the inertial measurement unit to the known plurality of motion conditions includes subjecting the inertial measurement unit to a rate of motion about at least one predetermined axis.

6. The method of claim 1, wherein subjecting the inertial measurement unit to the known plurality of motion conditions includes subjecting the inertial measurement unit to a rate of motion about three mutually perpendicular axes.

7. The method of claim 1, wherein subjecting the inertial measurement unit to the known plurality of environmental conditions includes subjecting the inertial measurement unit to known vibration conditions.

8. The method of claim 1, wherein subjecting the inertial measurement unit to the known plurality of environmental conditions includes subjecting the inertial measurement unit to known altitude conditions.

9. The method of claim 1, wherein subjecting the inertial measurement unit to the known plurality of environmental conditions includes subjecting the inertial measurement unit to known temperatures.

10. A method for calibrating a plurality of inertial measurement units, the method comprising:

mounting the plurality of inertial measurement units on a multi-axis rate table;

subjecting the plurality of inertial measurement units to known motion and environmental conditions;

determining any differences between outputs of the plurality of inertial measurement units and the known motion and environmental conditions, wherein determining is performed by a plurality of processors each connected internally to a respective inertial measurement unit of the plurality of inertial measurement units;

calculating, with the plurality of processors, a plurality of correction coefficients to be used to modify the outputs of the plurality of inertial measurement units; and

modifying the outputs of the plurality of inertial measurement units with the plurality of correction coefficients.

11. The method of claim 10, further comprising passing the outputs of each respective inertial measurement unit of the plurality of inertial measurement units to the processor connected internally to each respective inertial measurement unit without passing the outputs through any slip rings.

12. The method of claim 10, further comprising programming each of the plurality of inertial measurement units, via a prep-station, with test and calibration software.

13. The method of claim 12, further comprising inputting values of the known motion and environmental conditions, via the prep-station, in each of the plurality of inertial measurement units.

14. The method of claim 10, further comprising storing the correction coefficients in a memory device within each of the plurality of inertial measurement units, wherein each memory device stores at least one respective correction coefficient.

15. A method of performing calibration tests on an inertial measurement unit, the method comprising:

providing a processor internal to the inertial measurement unit;

connecting the processor to receive outputs of the inertial measurement unit, wherein the outputs of the inertial measurement unit do not pass through slip rings;

calculating correction coefficients at the processor; and

storing the correction coefficients at the inertial measurement unit.

16. The method of claim 15, further comprising modifying the outputs of the inertial measurement unit in accordance with the correction coefficients to produce more accurate outputs.

17. The method of claim 15, further comprising mounting the inertial measurement unit on a test table to supply predetermined known input values to the inertial measurement unit.

18. The method of claim 17, further comprising modifying the outputs of the inertial measurement unit in accordance with the correction coefficients to produce more accurate outputs.

19. The method of claim 15, further comprising mounting the inertial measurement unit on a three-axis table to supply predetermined known input rate values to the inertial measurement unit.

20. The method of claim 19, further comprising supplying various temperatures to the inertial measurement unit.