Cuboid inertial measurement unit

• US 10,473,464 B2
• Filed: 01/17/2019
• Issued: 11/12/2019
• Est. Priority Date: 01/17/2018
• Status: Active Grant

• Current Assignee: Cubic Defence UK Limited
• Original Assignee: Cubic Corporation
• Inventors: Fox, Andrew John, Parry, Matthew, Bradley, Byron
• Primary Examiner(s): Kwok, Helen C
• Application Number:
  US16/250,796
• Publication Number:
  US 20190219395A1
• Time in Patent Office: 299 Days
• CPC Class Codes: G01C 19/5776 Signal processing not specific to any of the devices covered by groups G01C19/5607 - G01C19/5719
• CPC Class Codes: G01C 19/5783 Mountings or housings not specific to any of the devices covered by groups G01C19/5607 - G01C19/5719
• CPC Class Codes: G01C 21/166 Mechanical, construction or arrangement details of inertial navigation systems

Abstract

An inertial measurement unit includes a substrate having MEMS gyroscopes arranged on the substrate as opposing pairs. The gyroscopes of each opposing pair are arranged on opposite sides of an axis of rotation of the substrate and each opposing pair has a central axis that intersects an axis of rotation of the substrate. A processor receives a rotational measurement from each gyroscope, compares the measurements from gyroscopes of each opposing pair, determines a mean or median rotation value for each opposing pair, and compares the mean or median rotation value with a threshold value. The processor assigns a weight to the mean or median value for each opposing pair and determines a rotation of the cuboid inertial measurement unit based on the mean or median value for each opposing pair and the respective weight for the mean or median value for each opposing pair.

Claims

1. An inertial measurement unit, comprising:

a substrate;

a plurality of MEMS gyroscopes arranged on the substrate as opposing pairs, wherein the MEMS gyroscopes of each of the opposing pairs of MEMS gyroscopes are arranged on opposite sides of an axis of rotation of the substrate, and wherein the MEMS gyroscopes of each of the opposing pairs of MEMS gyroscopes are oriented in opposite directions of one another; and

a processor that is configured to;

receive a rotational measurement from each of the plurality of MEMS gyroscopes;

compare the measurements from the MEMS gyroscopes of each of the opposing pairs with one another;

determine at least one of a mean or a median rotation value for the measurements of each of the opposing pairs of MEMS gyroscopes;

compare the at least one of the mean or the median rotation value with a threshold value;

remove one or more of the at least one of the mean or the median rotation values based on the comparison;

after removing the one or more of the at least one of the mean or median values, assign a weight to the at least one of the mean or the median value for each of the opposing pairs of MEMS gyroscopes; and

determine a rotation of the inertial measurement unit based on the at least one of the mean or the median value for each of the opposing pairs of MEMS gyroscopes and the respective weight for each of the at least one of the mean or the median value for each of the opposing pairs of MEMS gyroscopes.

2. The inertial measurement unit of claim 1, wherein:

the MEMS gyroscopes of each of the opposing pairs of MEMS gyroscopes are arranged symmetrically about the axis of rotation of the substrate.

3. The inertial measurement unit of claim 1, wherein:

the plurality of MEMS gyroscopes comprises a first opposing pair that is arranged about a first axis of rotation of the substrate and a second opposing pair that is arranged about a second axis of rotation of the substrate, the first axis of rotation being transverse to the second axis of rotation.

4. The inertial measurement unit of claim 1, wherein:

each of the opposing pairs has a central axis that intersects at least one axis of rotation of the substrate.

5. The inertial measurement unit of claim 1, further comprising:

a filter that is configured to eliminate a portion of noise detected by at least some of the opposing pairs.

6. The inertial measurement unit of claim 5, wherein:

the filter comprises a Kalman filter.

7. The inertial measurement unit of claim 1, wherein:

at least some the plurality of MEMS gyroscopes are aligned with one another in three dimensions.

8. A method of determining a rotation, comprising:

receiving a rotational measurement from each of a plurality of MEMS gyroscopes positioned on a substrate of a cuboid inertial measurement unit, wherein the plurality of MEMS gyroscopes are arranged on the substrate as opposing pairs, and wherein the MEMS gyroscopes of each of the opposing pairs of MEMS gyroscopes are oriented in opposite directions of one another;

comparing the measurements from the MEMS gyroscopes of each of the opposing pairs with one another;

determining at least one of a mean or a median rotation value for the measurements of each of the opposing pairs of MEMS gyroscopes;

comparing the at least one of the mean or the median rotation value with a threshold value;

removing one or more of the at least one of the mean or the median rotation values based on the comparison;

after removing the one or more of the at least one of the mean or median values, assigning a weight to the at least one of the mean or the median value for each of the opposing pairs of MEMS gyroscopes; and

determining a rotation of the cuboid inertial measurement unit based on the at least one of the mean or the median value for each of the opposing pairs of MEMS gyroscopes and the respective weight for each of the at least one of the mean or the median value for each of the opposing pairs of MEMS gyroscopes.

9. The method of determining a rotation of claim 8, further comprising:

applying a correction to at least one of the mean or the median rotation values prior to assigning the weight to the at least one of the mean or the median rotation values.

10. The method of determining a rotation of claim 8, wherein:

the weight for each of the at least one of the mean or the median value for each of the opposing pairs of MEMS gyroscopes is based at least in part on a proximity of each of the at least one of the mean or the median value for each of the opposing pairs of MEMS gyroscopes to an expected value.

11. The method of determining a rotation of claim 8, wherein:

a first weight is assigned when a sum of the measurements of the MEMS gyroscopes from a single opposing pair is zero;

a second weight is assigned when the sum of the measurements of the MEMS gyroscopes from a single opposing pair is non-zero; and

the first weight is greater than the second weight.

12. The method of determining a rotation of claim 8, wherein:

each of the opposing pairs has a central axis that intersects at least one axis of rotation of the substrate.

13. The method of determining a rotation of claim 8, wherein:

the inertial measurement unit further comprises a filter that is configured to eliminate a portion of noise detected by at least some of the opposing pairs.

14. An inertial measurement unit, comprising:

a substrate;

a plurality of MEMS gyroscopes arranged on the substrate as opposing pairs, wherein;

the MEMS gyroscopes of each of the opposing pairs of MEMS gyroscopes are arranged on opposite sides of an axis of rotation of the substrate;

the MEMS gyroscopes of each of the opposing pairs of MEMS gyroscopes are oriented in opposite directions of one another; and

the plurality of MEMS gyroscopes are configured to measure a rotation of the substrate;

at least one electrical circuit in communication with the plurality of MEMS gyroscopes;

a processor; and

a connector that is in communication with the at least one electrical circuit and that is coupled with the processor so as to electronically couple the plurality of MEMS gyroscopes with the processor, wherein the processor is configured to;

receive a rotational measurement from each of the plurality of MEMS gyroscopes;

compare the measurements from the MEMS gyroscopes of each of the opposing pairs with one another;

determine at least one of a mean or a median rotation value for the measurements of each of the opposing pairs of MEMS gyroscopes;

compare the at least one of the mean or the median rotation value with a threshold value;

remove one or more of the at least one of the mean or the median rotation values based on the comparison;

after removing the one or more of the at least one of the mean or median values, assign a weight to the at least one of the mean or the median value for each of the opposing pairs of MEMS gyroscopes; and

determine a rotation of the inertial measurement unit based on the at least one of the mean or the median value for each of the opposing pairs of MEMS gyroscopes and the respective weight for each of the at least one of the mean or the median value for each of the opposing pairs of MEMS gyroscopes.

15. The inertial measurement unit of claim 14, wherein:

the substrate comprises a printed circuit board.

16. The inertial measurement unit of claim 14, wherein:

the substrate comprises a top surface and a bottom surface; and

both MEMS gyroscopes of at least one opposing pair are positioned on the top surface or the bottom surface.

17. The inertial measurement unit of claim 14, wherein:

the substrate comprises a top surface and a bottom surface; and

a first MEMS gyroscope of at least one opposing pair is positioned on the top surface and a second MEMS gyroscope of the at least one opposing pair is positioned on the bottom surface.

18. The inertial measurement unit of claim 14, wherein:

each of the opposing pairs has a central axis that intersects at least one axis of rotation of the substrate.

19. The inertial measurement unit of claim 14, wherein:

at least some of the plurality of MEMS gyroscopes are arranged at approximately 45 degrees relative to one another.