Systems and methods for acceleration and rotational determination from an out-of-plane MEMS device

• US 7,971,483 B2
• Filed: 03/28/2008
• Issued: 07/05/2011
• Est. Priority Date: 03/28/2008
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Johnson, Burgess, Supino, Ryan
• Primary Examiner(s): Kwok; Helen C.
• Application Number:
  US12/057,695
• Publication Number:
  US 20090241662A1
• Time in Patent Office: 1,194 Days
• Field of Search: 735/040.4, 735/041.2, 735/041.4, 735/143.2, 735/10, 735/11, 735/040.3, 702/141
• US Class Current: 73/504.04
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis

Abstract

A Micro-Electro-Mechanical Systems (MEMS) inertial sensor systems and methods are operable to determine linear acceleration and rotation. An exemplary embodiment applies a first linear acceleration rebalancing force via a first electrode pair to a first proof mass, applies a second linear acceleration rebalancing force via a second electrode pair to a second proof mass, applies a first Coriolis rebalancing force via a third electrode pair to the first proof mass, applies a second Coriolis rebalancing force via a fourth electrode pair to the second proof mass, determines a linear acceleration corresponding to the applied first and second linear acceleration rebalancing forces, and determines a rotation corresponding to the applied first and second Coriolis rebalancing forces.

Claims

1. A method for determining linear acceleration and rotation of a Micro-Electro-Mechanical Systems (MEMS) inertial sensor, comprising:

applying a first linear acceleration rebalancing force via a first electrode pair to a first proof mass;

applying a second linear acceleration rebalancing force via a second electrode pair to a second proof mass;

applying a first Coriolis rebalancing force via a third electrode pair to the first proof mass;

applying a second Coriolis rebalancing force via a fourth electrode pair to the second proof mass;

determining a linear acceleration corresponding to the applied first and second linear acceleration rebalancing forces; and

determining a rotation corresponding to the applied first and second Coriolis rebalancing forces.

2. The method of claim 1, further comprising:

detecting a pick off voltage V_SPO from the first and second proof masses;

determining a rebalancing voltage V_ULS that is applied to a first electrode of the first electrode pair from the pick off voltage V_SPO;

determining a rebalancing voltage V_LLS that is applied to a second electrode of the first electrode pair from the pick off voltage V_SPO;

determining a rebalancing voltage V_URS that is applied to a first electrode of the second electrode pair from the pick off voltage V_SPO; and

determining a rebalancing voltage V_LRS that is applied to a second electrode of the second electrode pair from the pick off voltage V_SPO,

wherein the first linear acceleration rebalancing force at the first electrode pair corresponds to V_ULS and V_LLS, and wherein the second linear acceleration rebalancing force at the second electrode pair corresponds to V_URS and V_LRS.

3. The method of claim 2, further comprising:

determining the rebalancing voltage V_ULS in accordance with a first equation defined by V_ULS=−

V_SB−

V_A+V_p sin(ω

_pt);

determining the rebalancing voltage V_LLS in accordance with a second equation defined by V_LLS=V_SB−

V_A−

V_p sin(ω

_pt);

determining the rebalancing voltage V_URS in accordance with a third equation defined by V_URS=V_SB+V_A+V_p sin(ω

_pt); and

determining the rebalancing voltage V_LRS in accordance with a fourth equation defined by V_LRS=−

V_SB+V_A−

V_p sin(ω

_pt),

wherein V_SB is an applied voltage of a sense bias, where V_A is a voltage of the applied linear acceleration rebalancing force, where V_p is an applied AC pick off voltage, and where ω

_p is a frequency of the applied AC pick off voltage V_p.

4. The method of claim 1, further comprising:

detecting a pick off voltage V_SPO from the first and second proof masses;

determining a Coriolis voltage V_CUL that is applied to a first electrode of the third electrode pair from the pick off voltage V_SPO;

determining a Coriolis voltage V_CLL that is applied to a second electrode of the third electrode pair from the pick off voltage V_SPO;

determining a Coriolis voltage V_CUR that is applied to a first electrode of the fourth electrode pair from the pick off voltage V_SPO; and

determining a Coriolis voltage V_CLR that is applied to a second electrode of the fourth electrode pair from the pick off voltage V_SPO,

wherein the first Coriolis rebalancing force at the first electrode pair corresponds to V_CUL and V_CLL, and wherein the second Coriolis rebalancing force at the second electrode pair corresponds to V_CUR and V_CLR.

5. The method of claim 4, further comprising:

determining the Coriolis voltages V_CUL and V_CLR in accordance with a first equation defined by V_CUL=V_CLR=V_COR sin(ω

_mt/2); and

determining the Coriolis voltages V_CLL and V_CUR in accordance with a second equation defined by V_CLL=V_CUR=V_COR cos(ω

_mt/2),

wherein V_COR is a Coriolis voltage, and wherein ω

_mt/2 is one half of a frequency of a motor frequency of the first and second proof masses.

6. The method of claim 1, further comprising:

applying a first quadrature rebalancing force to the first proof mass via a fifth electrode pair and a sixth electrode pair; and

applying a second quadrature rebalancing force to the second proof mass via a seventh electrode pair and an eighth electrode pair.

7. The method of claim 1, further comprising:

applying an initialization rebalancing force to the first proof mass via the first electrode pair to move the first proof mass from a non-ideal position to an ideal position.

8. The method of claim 1, wherein the linear acceleration is determined from the applied first and second linear acceleration rebalancing forces, and wherein the rotation is determined from the applied first and second Coriolis rebalancing forces.

9. The method of claim 1, wherein the linear acceleration is determined from a change in a capacitance associated with the first electrode pair and the second electrode pair, and wherein the rotation is determined from a change in a capacitance associated with the third electrode pair and the fourth electrode pair.

10. A Micro-Electro-Mechanical Systems (MEMS) inertial sensor for determining linear acceleration and rotation, comprising:

a first proof mass;

a second proof mass;

a first electrode pair operable to apply a first linear acceleration rebalancing force to the first proof mass;

a second electrode pair operable to apply a second linear acceleration rebalancing force to the second proof mass;

a third electrode pair operable to apply a first Coriolis rebalancing force to the first proof mass; and

a fourth electrode pair operable to apply a second Coriolis rebalancing force to the second proof mass.

11. The MEMS inertial sensor of claim 10, further comprising:

a processing system operable to determine a linear acceleration from the applied first and second linear acceleration rebalancing forces and operable to determine a rotation from the applied first and second Coriolis rebalancing forces.

12. The MEMS inertial sensor of claim 10, further comprising:

an amplifier system communicatively coupled to the first proof mass and the second proof mass, and operable to output a pick off voltage V_SPO,

wherein a rebalancing voltage V_ULS that is applied to a first electrode of the first electrode pair is determinable from the pick off voltage V_SPO,

wherein a rebalancing voltage V_LLS that is applied to a second electrode of the first electrode pair is determinable from the pick off voltage V_SPO,

wherein a rebalancing voltage V_URS that is applied to a first electrode of the second electrode pair is determinable from the pick off voltage V_SPO,

wherein a rebalancing voltage V_LRS that is applied to a second electrode of the second electrode pair is determinable from the pick off voltage V_SPO, and

wherein the first linear acceleration rebalancing force at the first electrode pair corresponds to V_ULS and V_LLS, and wherein the second linear acceleration rebalancing force at the second electrode pair corresponds to V_URS and V_LRS.

13. The MEMS inertial sensor of claim 12, further comprising:

a first pick off amplifier system communicatively coupled to the first electrode of the first electrode pair and operable to output a voltage V_ULSP;

a second pick off amplifier system communicatively coupled to the second electrode of the first electrode pair and operable to output a voltage V_LLSP;

a third pick off amplifier system communicatively coupled to the first electrode of the second electrode pair and operable to output a voltage V_URSP; and

a fourth pick off amplifier system communicatively coupled to the second electrode of the second electrode pair and operable to output a voltage V_LRSP.

14. The MEMS inertial sensor of claim 10, further comprising:

an amplifier system communicatively coupled to the first proof mass and the second proof mass, and operable to output a pick off voltage V_SPO,

wherein a Coriolis voltage V_CUL that is applied to a first electrode of the third electrode pair is determinable from the pick off voltage V_SPO,

wherein a Coriolis voltage V_CLL that is applied to a second electrode of the third electrode pair is determinable from the pick off voltage V_SPO,

wherein a Coriolis voltage V_CUR that is applied to a first electrode of the fourth electrode pair is determinable from the pick off voltage V_SPO,

wherein a Coriolis voltage V_CLR that is applied to a second electrode of the fourth electrode pair is determinable from the pick off voltage V_SPO, and

wherein the first Coriolis rebalancing force at the first electrode pair corresponds to V_CUL and V_CLL, and wherein the second Coriolis rebalancing force at the second electrode pair corresponds to V_CUR and V_CLR.

15. A method for determining linear acceleration and rotation of a Micro-Electro-Mechanical Systems (MEMS) gyroscope, comprising:

sensing a change in a first capacitance between a first electrode of a first electrode pair and a first proof mass;

sensing a change in a second capacitance between a second electrode of the first electrode pair and the first proof mass;

sensing a change in a third capacitance between a first electrode of a second electrode pair and a second proof mass;

sensing a change in a fourth capacitance between a second electrode of the second electrode pair and the second proof mass;

sensing a change in a fifth capacitance between a first electrode of a third electrode pair and the first proof mass;

sensing a change in a sixth capacitance between a second electrode of the third electrode pair and the first proof mass;

sensing a change in a seventh capacitance between a first electrode of a fourth electrode pair and the second proof mass; and

sensing a change in an eighth capacitance between a second electrode of the fourth electrode pair and the second proof mass.

16. The method of claim 15, further comprising:

determining a linear acceleration from the sensed first capacitance, the sensed second capacitance, the sensed third capacitance, and the sensed fourth capacitance.

17. The method of claim 16, further comprising:

determining a linear acceleration rebalancing force from the determined linear acceleration;

applying the linear acceleration rebalancing force via the first electrode pair to the first proof mass; and

applying the linear acceleration rebalancing force via the second electrode pair to the second proof mass.

18. The method of claim 15, further comprising:

determining a rotation from the sensed fifth capacitance, the sensed sixth capacitance, the sensed seventh capacitance, and the sensed eighth capacitance.

19. The method of claim 18, further comprising:

determining a Coriolis rebalancing force from the determined rotation;

applying the Coriolis rebalancing force via the third electrode pair to the first proof mass; and

applying the Coriolis rebalancing force via the fourth electrode pair to the second proof mass.