ANGULAR RATE SENSOR WITH QUADRATURE ERROR COMPENSATION

• US 20140007681A1
• Filed: 07/09/2012
• Published: 01/09/2014
• Est. Priority Date: 07/09/2012
• Status: Active Grant

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Inventors: Lin, Yizhen
• Granted Patent: US 9,310,202 B2
• Time in Patent Office: Days
• US Class Current: 73/504.12
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis
• CPC Class Codes: G01C 19/5733 Structural details or topology

Abstract

An angular rate sensor (20) includes a drive mass (36) flexibly coupled to a substrate (22). A sense mass (42) is suspended above the substrate (22) is and flexibly connected to the drive mass (36) via flexible support elements (44). A quadrature compensation electrode (24) is associated with the drive mass (36) and a sense electrode (28) is associated with the sense mass (42). The drive mass (36) and the sense mass (42) oscillate together relative to a sense axis (50) in response to quadrature error. The quadrature error produces a signal error component (78) between the quadrature compensation electrode (24) and the drive mass (36) and a signal error component (76) between the sense electrode (28) and the sense mass (42). The compensation and sense electrodes (24, 28) are coupled in reverse polarity so that the signal error component (78) substantially cancels the signal error component (76).

Claims

1. An angular rate sensor comprising:

a substrate;

a drive mass flexibly coupled to said substrate;

a sense mass suspended above said substrate and flexibly connected to said drive mass via flexible support elements;

a first electrode associated with said drive mass; and

a second electrode associated with said sense mass, said second electrode being electrically coupled to said first electrode in reverse polarity so that a first error component between said first electrode and said drive mass substantially cancels a second error component between said second electrode and said sense mass.

2. An angular rate sensor as claimed in claim 1 wherein:

said drive mass together with said sense mass are configured to move with an oscillatory motion relative to a drive axis;

said flexible support elements enable said sense mass to oscillate relative to a sense axis that is perpendicular to said drive axis in response to an angular velocity about an input axis that is perpendicular to each of said drive and said sense axes; and

said drive mass together with said sense mass oscillate relative to said sense axis in response to quadrature error, said quadrature error producing said first error component at said first electrode and said second error component at said second electrode.

3. An angular rate sensor as claimed in claim 1 wherein:

said first electrode is a quadrature compensation electrode; and

said second electrode is a sense electrode.

4. An angular rate sensor as claimed in claim 1 further comprising a positive output terminal electrically coupled with said second electrode, wherein said second electrode is a positive pole of said angular rate sensor and said first electrode is a negative pole of said angular rate sensor.

5. An angular rate sensor as claimed in claim 4 further comprising:

a third electrode associated with said drive mass;

a fourth electrode associated with said sense mass, said fourth electrode being electrically coupled to said third electrode; and

a negative output terminal electrically coupled with said fourth electrode, wherein said fourth electrode is a negative pole of said angular rate sensor and said third electrode is a positive pole of said angular rate sensor so that a third error component between said drive mass and said third electrode substantially cancels a fourth error component between said sense mass and said fourth electrode.

6. An angular rate sensor as claimed in claim 1 wherein:

said drive mass includes first and second regions separated by an axis of rotation oriented parallel to a surface of said substrate;

said sense mass includes third and fourth regions separated by said axis of rotation, said first and third regions being laterally disposed on a first side of said axis of rotation, and said second and fourth regions being laterally disposed on a second side of said axis of rotation;

said first electrode is disposed beneath said first region; and

said second electrode is disposed beneath said fourth region.

7. An angular rate sensor as claimed in claim 6 wherein:

said first electrode is fixedly attached to said first region of said drive mass or to said substrate underlying said first region; and

said second electrode is fixedly attached to said fourth region of said sense mass or to said substrate underlying said sense mass.

8. An angular rate sensor as claimed in claim 6 further comprising:

a third electrode associated with said drive mass and disposed beneath said second region; and

a fourth electrode associated with said sense mass and disposed beneath said third region, said third electrode being coupled to said fourth electrode so that a third error component between said drive mass and said third electrode substantially cancels a fourth error component between said sense mass and said fourth electrode.

9. An angular rate sensor as claimed in claim 6 wherein said axis of rotation is a sense axis, and said drive mass together with said sense mass are configured to move with said oscillatory motion about a drive axis that is perpendicular to said surface, and said flexible support elements enable said sense mass to oscillate about said sense axis in response to an angular velocity about an input axis that is perpendicular to each of said sense and drive axes.

10. An angular rate sensor as claimed in claim 1 wherein:

said first electrode is fixedly attached to said substrate and is laterally disposed away from a first edge of said drive mass to form a first gap between said first electrode and said first edge;

said second electrode is fixedly attached to said substrate and is laterally disposed away from a second edge of said sense mass to form a second gap between said second electrode and said second edge; and

said drive mass together with said sense mass are configured to move substantially parallel to a surface of said substrate along a drive axis, said flexible support elements enable said sense mass to oscillate substantially parallel to said surface of said substrate along a sense axis that is perpendicular to said drive axis in response to an angular velocity about an input axis that is perpendicular to said surface of said substrate.

11. An angular rate sensor as claimed in claim 10 wherein:

said first electrode and said first edge of said drive mass are longitudinally aligned with said drive axis; and

said second electrode and said second edge of said sense mass are longitudinally aligned with said drive axis.

12. An angular rate sensor as claimed in claim 10 wherein:

said first gap exhibits a first width;

said second gap exhibits a second width;

said drive mass together with said sense mass oscillate along said sense axis in response to quadrature error, said quadrature error producing said first error component at said first electrode and said second error component at said second electrode;

when said drive mass and said sense mass oscillate together in a first direction along said sense axis, said first gap width increases and said second gap width decreases, and

when said drive mass and said sense mass oscillate together in a second direction opposing said first direction, said first gap width decreases and said second gap width increases.

13. A method of compensating for quadrature error in an angular rate sensor, said angular rate sensor including a drive mass flexibly coupled to a substrate and a sense mass suspended above said substrate and flexibly connected to said drive mass via flexible support elements, said method comprising:

disposing a compensation electrode proximate said drive mass;

disposing a sense electrode proximate said sense mass; and

electrically coupling said compensation electrode with said sense electrode in reverse polarity so that a first error component between said compensation electrode and said drive mass substantially cancels a second error component between said sense electrode and said sense mass.

14. A method as claimed in claim 13 wherein said compensation electrode is a first compensation electrode, said sense electrode is a first sense electrode, and said method further comprises:

disposing a second compensation electrode proximate said drive mass;

disposing a second sense electrode proximate said sense mass; and

electrically coupling said second compensation electrode with said second sense electrode in said reverse polarity so that a third error component between said second compensation electrode and said drive mass substantially cancels a fourth error component between said second sense electrode and said sense mass.

15. A method as claimed in claim 14 wherein said angular rate sensor further includes a positive output terminal and a negative output terminal, and said method further comprises:

electrically coupling said positive output terminal with said first sense electrode, said first sense electrode being a positive sense pole of said angular rate sensor and said first compensation electrode being a negative compensation pole of said angular rate sensor; and

electrically coupling a negative output terminal with said second sense electrode, said second sense electrode being a negative sense pole of said angular rate sensor and said second compensation electrode being a positive compensation pole of said angular rate sensor.

16. An angular rate sensor comprising:

a substrate;

a drive mass flexibly coupled to said substrate;

a sense mass suspended above said substrate and flexibly connected to said drive mass via flexible support elements, said drive mass and sense mass moving together in oscillatory motion relative to a drive axis, said flexible support elements enabling said sense mass to oscillate relative to a sense axis that is perpendicular to said drive axis in response to an angular velocity about an input axis that is perpendicular to each of said drive and said sense axes, and said drive and sense masses oscillating together relative to said sense axis in response to quadrature error;

a quadrature compensation electrode associated with said drive mass, said quadrature error producing a first error component at said quadrature compensation electrode;

a sense electrode associated with said sense mass, said quadrature error producing a second error component at said sense electrode, said sense electrode being electrically coupled to said quadrature compensation electrode in reverse polarity so that said first error component between said quadrature compensation electrode and said drive mass substantially cancels said second error component between said sense electrode and said sense mass; and

a positive output terminal electrically coupled with said sense electrode, wherein said sense electrode is a positive sense pole of said angular rate sensor and said quadrature compensation electrode is a negative compensation pole of said angular rate sensor.

17. An angular rate sensor as claimed in claim 16 wherein:

said drive mass includes first and second regions separated by an axis of rotation oriented parallel to a surface of said substrate;

said sense mass includes third and fourth regions separated by said axis of rotation, said first and third regions being laterally disposed on a first side of said axis of rotation, and said second and fourth regions being laterally disposed on a second side of said axis of rotation;

said quadrature compensation electrode is disposed beneath said first region; and

said sense electrode is disposed beneath said fourth region.

18. An angular rate sensor as claimed in claim 17 wherein said quadrature compensation electrode is a first compensation electrode, said sense electrode is a first sense electrode, and said sensor further comprises:

a second compensation electrode associated with said drive mass and disposed beneath said second region, said quadrature error producing a third error component between said drive mass and said second compensation electrode;

a second sense electrode associated with said sense mass and disposed beneath said third region, said quadrature error producing a fourth error component between said sense mass and said second sense electrode, said second compensation electrode being coupled to said second sense electrode in reverse polarity so that said third error component substantially cancels said fourth error component; and

a negative output terminal electrically coupled with said second sense electrode, wherein said second sense electrode is a negative sense pole of said angular rate sensor and said second compensation electrode is a positive compensation pole of said angular rate sensor.

19. An angular rate sensor as claimed in claim 16 wherein:

said quadrature compensation electrode is fixedly attached to said substrate and is laterally disposed away from a first edge of said drive mass to form a first gap between said quadrature compensation electrode and said first edge;

said sense electrode is fixedly attached to said substrate and is laterally disposed away from a second edge of said sense mass to form a second gap between said sense electrode and said second edge; and

said drive mass together with said sense mass are configured to move substantially parallel to a surface of said substrate along a drive axis, said flexible support elements enable said sense mass to oscillate substantially parallel to said surface of said substrate along a sense axis that is perpendicular to said drive axis in response to an angular velocity about an input axis that is perpendicular to said surface of said substrate.

20. An angular rate sensor as claimed in claim 19 wherein:

said first gap exhibits a first width;

said second gap exhibits a second width;

when said drive mass and said sense mass oscillate together in a first direction along said sense axis in response to said quadrature error, said first gap width increases and said second gap width decreases, and

when said drive mass and said sense mass oscillate together in a second direction opposing said first direction in response to said quadrature error, said first gap width decreases and said second gap width increases.