INTEGRATED RATE ISOLATION SENSOR

• US 20110172950A1
• Filed: 01/14/2010
• Published: 07/14/2011
• Est. Priority Date: 01/14/2009
• Status: Active Grant

• Current Assignee: Charles Stark Draper Laboratory Incorporated, United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Original Assignee: Charles Stark Draper Laboratory Incorporated
• Inventors: Henderson, Timothy, Crain, Tim, Brady, Tye, Zimpfer, Doug, Phillips, Richard
• Granted Patent: US 8,290,744 B2
• Time in Patent Office: Days
• US Class Current: 702/141
• CPC Class Codes: G01C 21/188 for accumulated errors, e.g. by coupling inertial systems with absolute positioning systems
• CPC Class Codes: G01C 25/005 initial alignment, calibration or starting-up of inertial devices

Abstract

In one embodiment, a system for providing fault-tolerant inertial measurement data includes a sensor for measuring an inertial parameter and a processor. The sensor has less accuracy than a typical inertial measurement unit (IMU). The processor detects whether a difference exists between a first data stream received from a first inertial measurement unit and a second data stream received from a second inertial measurement unit. Upon detecting a difference, the processor determines whether at least one of the first or second inertial measurement units has failed by comparing each of the first and second data streams to the inertial parameter.

Claims

1. A system for providing fault-tolerant inertial measurement data, the system comprising:

a sensor, having less accuracy than an inertial measurement unit, for measuring an inertial parameter; and

a processor for (i) detecting whether a difference exists between a first data stream received from a first inertial measurement unit and a second data stream received from a second inertial measurement unit, and (ii) upon detecting a difference, determining whether at least one of the first or second inertial measurement units has failed by comparing each of the first and second data streams to the inertial parameter.

2. The system of claim 1, wherein the first and second data streams represent measurements of the same parameter.

3. The system of claim 1, wherein the sensor comprises at least one of a gyroscope or an accelerometer.

4. The system of claim 1, wherein the sensor comprises a MEMS device.

5. The system of claim 1, wherein the sensor comprises an x-axis gyroscope, a y-axis gyroscope, and a z-axis gyroscope.

6. The system of claim 1, wherein the sensor, in comparison to either the first inertial measurement unit or the second inertial measurement unit, consumes less than at least one of power, area, or volume.

7. The system of claim 1, wherein the sensor has an order of magnitude less accuracy than the first and second inertial measurement units.

8. The system of claim 1, further comprising an output for indicating whether a failure has been determined.

9. The system of claim 1, further comprising a display for displaying a status of at least one of the sensor, the first inertial measurement unit, or the second inertial measurement unit.

10. The system of claim 1, wherein the processor further combines at least two of the inertial parameter, the first data stream, and the second data stream to provide an inertial measurement data output.

11. A processor for providing fault-tolerant inertial measurement data, the processor comprising:

at least one input for receiving first and second data streams from first and second inertial measurement unit, respectively;

circuitry for (i) detecting whether a difference exists between the first and second data streams, and (ii) upon detecting a difference, determining whether at least one of the first or second inertial measurement units has failed by comparing each of the first and second data streams to the output of a sensor having less accuracy than the first and second inertial measurement units; and

an output for providing inertial measurement data based on the determination.

12. The processor of claim 11, wherein the inertial measurement data comprises a combination of at least two of the first data stream, the second data stream, and the output of the sensor.

13. The processor of claim 11, wherein the inertial measurement data consists essentially of the output of the sensor.

14. The processor of claim 11, further comprising an error output for indicating the determination of a failure.

15. The processor of claim 11, wherein the sensor has an order of magnitude less accuracy than the first and second inertial measurement units.

16. A fault-tolerant system for determining a position of a vehicle, the system comprising:

a first inertial measurement unit for providing a first rate stream;

a second inertial measurement unit for providing a second rate stream;

a sensor, having less accuracy than the first and second inertial measurement units, for measuring an inertial parameter; and

a processor for (i) detecting whether a difference exists between the first and second rate streams, and (ii) upon detecting a difference, determining whether at least one of the first or second inertial measurement units has failed by comparing each of the first and second rate streams to the inertial parameter.

17. The fault-tolerant system of claim 16, wherein the vehicle is selected from the group consisting of a spacecraft, a satellite, an aircraft, a boat, and a ground-based vehicle.

18. The fault-tolerant system of claim 16, wherein the processor further disables a failed inertial measurement unit.

19. The fault-tolerant system of claim 16, further comprising a display for displaying a status of at least one of the sensor, the first inertial measurement unit, or the second inertial measurement unit.

20. A method for providing fault-tolerant inertial measurement data, the method comprising:

receiving, at a processor, a first data stream from a first inertial measurement unit and a second data stream from a second inertial measurement unit;

detecting whether a difference between the first and second data streams exists;

upon detecting a difference, determining whether at least one of the first or second inertial measurement units has failed by comparing each of the first and second data streams to an output of a sensor having less accuracy than the first and second inertial measurement units; and

implementing a corrective action upon determining that an inertial measurement unit has failed.

21. The method of claim 20, wherein the corrective action comprises disabling the failed inertial measurement unit.

22. The method of claim 20, wherein the corrective action comprises outputting an error signal.

23. The method of claim 20, wherein determining whether at least one of the first or second inertial measurement units has failed comprises performing at least one of sensor-level identification or box-level identification.

24. The method of claim 20, further comprising comparing the detected difference to a threshold.

25. The method of claim 24, wherein the threshold is user-defined.

26. The method of claim 20, wherein the sensor, in comparison to either the first inertial measurement unit or the second inertial measurement unit, consumes less than at least one of power, area, or volume.