TECHNIQUE TO IMPROVE NAVIGATION PERFORMANCE THROUGH CAROUSELLING

• US 20100256907A1
• Filed: 04/06/2009
• Published: 10/07/2010
• Est. Priority Date: 04/06/2009
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Bye, Charles T.
• Granted Patent: US 9,599,474 B2
• Time in Patent Office: Days
• US Class Current: 701/221
• CPC Class Codes: G01C 21/165 combined with non-inertial navigation instruments
• CPC Class Codes: G01C 21/183 Compensation of inertial measurements, e.g. for temperature effects
• CPC Class Codes: G01C 21/185 for gravity
• CPC Class Codes: G01C 21/188 for accumulated errors, e.g. by coupling inertial systems with absolute positioning systems
• CPC Class Codes: G01C 25/00 Manufacturing, calibrating, cleaning, or repairing instruments or devices referred to in the other groups of this subclass testing, calibrating or compensating compasses G01C17/38

Abstract

A method to improve estimation and stabilization of heading in an inertial navigation system is provided. The method includes operating an inertial measurement unit oriented in a first orientation, forward-rotating the operational inertial measurement unit by a selected-rotation angle about a Z-body axis of the inertial navigation system, wherein the inertial measurement unit is oriented in a second orientation, operating the inertial measurement unit oriented in the second orientation, reverse-rotating the operational inertial measurement unit by the selected-rotation angle about the Z-body axis, wherein the inertial measurement unit is oriented in the first orientation, continuously receiving information indicative of an orientation of the inertial measurement unit at a rotational compensator, and continuously-rotationally compensating navigation module output at the rotational compensator, wherein output of the rotational compensator is independent of the rotating.

Claims

1. A method to improve estimation and stabilization of heading in an inertial navigation system, the method comprising:

operating an inertial measurement unit oriented in a first orientation;

forward-rotating the operational inertial measurement unit by a selected-rotation angle about a Z-body axis of the inertial navigation system, wherein the inertial measurement unit is oriented in a second orientation;

operating the inertial measurement unit oriented in the second orientation;

reverse-rotating the operational inertial measurement unit by the selected-rotation angle about the Z-body axis, wherein the inertial measurement unit is oriented in the first orientation;

continuously receiving information indicative of an orientation of the inertial measurement unit at a rotational compensator; and

continuously-rotationally compensating navigation module output at the rotational compensator, wherein output of the rotational compensator is independent of the rotating.

2. The method of claim 1, wherein continuously receiving information indicative of the orientation of the inertial measurement unit at the rotational compensator comprises receiving information indicative of a current orientation of the inertial measurement unit while the inertial measurement unit is operating in the first orientation and the second orientation, and while the inertial measurement unit is forward-rotating and reverse-rotating, and

wherein continuously-rotationally compensating navigation module output comprises removing the effect of the rotation from the output of a navigation module while the inertial measurement unit is operating in the first orientation and the second orientation, and while the inertial measurement unit is forward-rotating and reverse-rotating.

3. The method of claim 1, further comprising operating the inertial measurement unit reoriented in the first orientation.

4. The method of claim 1, further comprising:

driving a rotational device to rotate about the z-body axis to a specified orientation, wherein the fixedly attached inertial measurement unit is rotated; and

measuring the orientation of the rotational device.

5. The method of claim 1, further comprising controlling the forward-rotating and the reverse-rotating of the rotational device by a rotational control algorithm.

6. The method of claim 5, wherein the rotational control algorithm is a timing algorithm, the method further comprising:

indicating a start-time of the forward-rotating and a forward-direction of rotation;

indicating a stop-time of the forward-rotating, wherein the inertial measurement unit moves from the first orientation to the second orientation between the start-time and the stop-time of the forward-rotating;

indicating a start time of the reverse-rotating and a reverse-direction of rotation; and

indicating a stop time of the reverse-rotating, wherein the inertial measurement unit moves from the second orientation to the first orientation between the start-time and the stop-time of the reverse-rotating.

7. The method of claim 5, further comprising sensing the forward-rotating and the reverse-rotating at a rotational position sensor.

8. The method of claim 1, receiving position input for a vehicle housing the inertial measurement unit from an aiding sensor co-located with the inertial measurement unit.

9. The method of claim 1, wherein forward-rotating the operational inertial measurement unit by the selected-rotation angle about the Z-body axis includes forward-rotating the operational inertial measurement unit in more than one rotational step;

and

wherein reverse-rotating the operational inertial measurement unit by the selected-rotation angle about the Z-body axis includes reverse-rotating the operational inertial measurement unit in respective more than one rotational steps.

10. The method of claim 9, wherein the selected-rotation angle is 90 degrees and there are four rotational steps per forward-rotating and an associated four rotational steps per reverse-rotating.

11. The method of claim 1, wherein the selected-rotation angle is one hundred eighty degrees.

16. The inertial navigation system of claim 9, wherein the rotational device is configured to rotate the inertial measurement unit by one hundred eighty degrees from a first orientation to a second orientation in at least one rotation step.

17. The inertial navigation system of claim 9, wherein the inertial measurement unit is a micro-electro-mechanical system (MEMS) inertial measurement unit.

12. An inertial navigation system, comprising:

an inertial measurement unit including orthogonally mounted gyroscopes;

a rotational device on which the inertial measurement unit is positioned, the rotational device configured to rotate the inertial measurement unit about a Z-body axis of the inertial navigation system from a first orientation to a second orientation;

a rotational position sensor to sense the orientation of one of the inertial measurement unit or the rotational device; and

a software module configured to remove the effect of the rotation of the inertial measurement unit and to generate error correction data, wherein gyroscope bias errors are distributed based on consecutive operations of the inertial measurement unit in the first orientation and the second orientation, and wherein a heading error of the inertial navigation system is reduced by the distribution of the gyroscope bias errors, the reduction being maximized when the Z-body axis of the inertial navigation system is parallel to a vertical-earth axis.

13. The inertial navigation system of claim 12, wherein the software module includes:

a rotational control algorithm to control the rotation of the rotational device;

a sensor compensation module to receive input from the inertial measurement unit;

a navigation module configured to receive input from the sensor compensation module;

a rotational compensator to receive information indicative of the orientation of the inertial measurement unit from the rotational position sensor and from the rotational control algorithm, and to compensate for the rotation of the inertial measurement unit about the Z-body axis, wherein navigational data output from the rotational compensator is independent of the orientation of the inertial measurement unit; and

a Kalman filter communicatively coupled to send error correction data to the navigation module, the sensor compensation module, the rotational control algorithm, and the rotational compensator.

14. The inertial navigation system of claim 12, further comprising an aiding sensor to input information to the Kalman filter.

15. The inertial navigation system of claim 12, wherein the inertial measurement unit includes a first-horizontal-sensing gyroscope, a second-horizontal-sensing gyroscope, and a vertical-sensing gyroscope, the gyroscopes being orthogonally mounted.

18. A computer readable medium embodying a program of instructions executable by a processor to perform a method comprising:

generating instructions to rotate a rotational device fixedly attached to an inertial measurement unit;

receiving information indicative of the orientation of the inertial measurement unit;

generating navigation data based on input received from the inertial measurement unit;

removing rotational effects from the generated navigation data based on the information indicative of the orientation of the inertial measurement unit;

outputting navigation data that is independent of the rotation of the inertial measurement unit; and

generating error correction data.

19. The computer readable medium of claim 18, further embodying a program of instructions executable by a processor to perform a method comprising sending the error correction data to a sensor compensation module, and a navigation module.

20. The computer readable medium of claim 19, further embodying a program of instructions executable by a processor to perform a method comprising sending the error correction data to a rotational compensator and a rotational control algorithm.