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

• US 7,984,648 B2
• Filed: 07/31/2008
• Issued: 07/26/2011
• Est. Priority Date: 04/10/2008
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Horning, Bob D., Supino, Ryan
• Primary Examiner(s): Kwok; Helen C.
• Application Number:
  US12/183,617
• Publication Number:
  US 20090255336A1
• Time in Patent Office: 1,090 Days
• Field of Search: 735/040.4, 735/040.3, 735/041.2, 735/041.4, 735/143.2, 735/10, 735/11, 702/141
• 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: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 15/18 in two or more dimensions

Abstract

A Micro-Electro-Mechanical Systems (MEMS) inertial sensor systems and methods determine linear acceleration and rotation in the in-pane and out-of-plane directions of the MEMS inertial sensor. An out-of-plane linear acceleration of the MEMS sensor may be sensed with the first out-of-plane electrode pair and the second out-of-plane electrode pair. An in-plane rotation of the MEMS sensor may be sensed with the first out-of-plane electrode pair and the second out-of-plane electrode. An in-plane linear acceleration of the MEMS sensor may be sensed with the first in-plane sense comb and the second in-plane sense comb. An out-of-plane rotation of the MEMS sensor may be sensed with the first in-plane sense comb and the second in-plane sense comb.

Claims

1. A method of sensing linear accelerations and rotations of a Micro-Electro-Mechanical Systems (MEMS) sensor comprising a first proof mass and a second proof mass aligned in an inplane axis, a first out-of-plane electrode pair with the first proof mass disposed therebetween, a second out-of-plane electrode pair with the second proof mass disposed therebetween, a first inplane sense comb with a plurality of comb fingers interleaved with opposing first proof mass comb fingers, and a second in-plane sense comb with a plurality of comb fingers interleaved with the opposing second proof mass comb fingers, the method comprising:

sensing an out-of-plane linear acceleration of the MEMS sensor with the first out-of-plane electrode pair and the second out-of-plane electrode pair;

sensing an in-plane rotation of the MEMS sensor with the first out-of-plane electrode pair and the second out-of-plane electrode pair;

sensing an in-plane linear acceleration of the MEMS sensor with the first in-plane sense comb and the second in-plane sense comb; and

sensing an out-of-plane rotation of the MEMS sensor with the first in-plane sense comb and the second in-plane sense comb.

2. The method of claim 1, further comprising:

sensing the out-of-plane linear acceleration and the in-plane linear acceleration from a common mode movement of the first and the second proof masses; and

sensing the out-of-plane rotation and the in-plane rotation from a differential mode movement of the first and the second proof masses.

3. The method of claim 1, further comprising:

driving the first proof mass in an oscillatory motion along the in-plane axis; and

driving the second proof mass in an opposing oscillatory motion along the in-plane axis, the opposing oscillatory motion substantially 180 degrees out of phase from the oscillatory motion of the first proof mass.

4. The method of claim 1, wherein sensing the out-of-plane linear acceleration of the MEMS sensor with the first out-of-plane electrode pair and the second out-of-plane electrode pair comprises:

sensing an out-of-plane linear acceleration of the first proof mass with the first out-of-plane electrode pair; and

sensing an out-of-plane linear acceleration of the second proof mass with the second out-of-plane electrode pair.

5. The method of claim 4, further comprising:

applying a first rebalancing force in response to sensing the out-of-plane linear acceleration of the first proof mass with the first out-of-plane electrode pair, the applied first rebalancing force repositioning the first proof mass to a predefined position of the first proof mass; and

applying a second rebalancing force in response to sensing the out-of-plane linear acceleration of the second proof mass with the second out-of-plane electrode pair, the applied second rebalancing force repositioning the second proof mass to a predefined position of the second proof mass.

6. The method of claim 5, further comprising:

determining the out-of-plane linear acceleration of the MEMS sensor based upon the applied first rebalancing force and the applied second rebalancing force.

7. The method of claim 5, wherein applying the first and second rebalancing forces comprises:

applying a first DC voltage signal to the first out-of-plane electrode pair; and

applying a second DC voltage signal to the second out-of-plane electrode pair.

8. The method of claim 5, further comprising:

applying a first Coriolis rebalancing force to the first proof mass with a third out-of-plane electrode pair; and

applying a second Coriolis rebalancing force to the second proof mass with a fourth out-of-plane electrode pair.

9. The method of claim 1, wherein sensing the in-plane rotation of the MEMS sensor with the first out-of-plane electrode pair and the second out-of-plane electrode pair comprises:

sensing an in-plane rotation of the first proof mass with the first out-of-plane electrode pair; and

sensing an in-plane rotation of the second proof mass with the second out-of-plane electrode pair.

10. The method of claim 9, further comprising:

applying a first rebalancing force in response to sensing the in-plane rotation of the first proof mass with the first out-of-plane electrode pair, the applied first rebalancing force repositioning the first proof mass to a predefined position of the first proof mass; and

applying a second rebalancing force in response to sensing the in-plane rotation of the second proof mass with the second out-of-plane electrode pair, the applied second rebalancing force repositioning the second proof mass to a predefined position of the second proof mass.

11. The method of claim 10, further comprising:

determining the in-plane rotation of the MEMS sensor based upon the applied first rebalancing force and the applied second rebalancing force.

12. The method of claim 1, wherein sensing the in-plane linear acceleration of the MEMS sensor with the first in-plane sense comb and the second in-plane sense comb comprises:

sensing an in-plane linear acceleration of the first proof mass with the first in-plane sense comb; and

sensing an in-plane linear acceleration of the second proof mass with the second inplane sense comb.

13. The method of claim 1, wherein sensing the out-of-plane rotation of the MEMS sensor with the first in-plane sense comb and the second in-plane sense comb comprises:

sensing an out-of-plane rotation of the first proof mass with the first in-plane sense comb; and

sensing an out-of-plane rotation of the second proof mass with the second in-plane sense comb.

14. The method of claim 1, further comprising:

applying a first quadrature rebalancing force to the first proof mass with a third out-of-plane electrode pair; and

applying a second quadrature rebalancing force to the second proof mass with a fourth out-of-plane electrode pair.

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

a first proof mass with a plurality of in-plane comb fingers and a first drive comb configured to drive the first proof mass in an oscillatory motion along an in-plane axis;

a second proof mass aligned with the first proof mass along the in-plane axis, the second proof mass with a plurality of in-plane comb fingers and a second drive comb configured to drive the second proof mass in an opposing oscillatory motion along the in-plane axis, the opposing oscillatory motion substantially 180 degrees out of phase from the oscillatory motion of the first proof mass;

a first out-of-plane electrode pair with the first proof mass disposed therebetween, the first out-of-plane electrode pair configured to sense a first out-of-plane motion of the first proof mass corresponding to an in-plane rotation of the MEMS sensor, and configured to sense a second out-of-plane motion of the first proof mass corresponding to a first out-of-plane linear acceleration of the MEMS sensor mass;

a second out-of-plane electrode pair with the second proof mass disposed therebetween, the second out-of-plane electrode pair configured to sense a first out-of-plane motion of the second proof mass corresponding to an in-plane rotation of the MEMS sensor, and configured to sense a second out-of-plane motion of the second proof mass corresponding to a second out-of-plane linear acceleration of the MEMS sensor;

a first in-plane sense comb with a plurality of comb fingers interleaved with the opposing first proof mass comb fingers, the first in-plane sense comb configured to sense an in-plane motion of the first proof mass corresponding to an out-of-plane rotation of the first proof mass, and configured to sense an in-plane motion of the first proof mass corresponding to an in-plane linear acceleration of the first proof mass; and

a second in-plane sense comb with a plurality of comb fingers interleaved with the opposing second proof mass comb fingers, the second in-plane sense comb configured to sense an out-of-plane rotation of the second proof mass, and configured to sense an in-plane linear acceleration of the second proof mass.

16. The MEMS inertial sensor of claim 15, wherein at least one of the first and the second out-of-plane electrode pairs with the first proof mass disposed therebetween, the at least one of the first and second out-of-plane electrode pairs configured to exert an initialization rebalancing force to the first proof mass.

17. The MEMS inertial sensor of claim 15, further comprising:

a processing device coupled to the at least one of the first and the second out-of-plane electrode pairs, and configured to determine a first capacitance between an upper one of the first and the second out-of-plane electrode pairs, configured to determine a second capacitance between a lower one of the first and the second out-of-plane electrode pairs, and configured to determine the initialization rebalancing force exerted to the first proof mass.

18. The MEMS inertial sensor of claim 15, further comprising:

an amplifier system coupled to the first proof mass and the second proof mass, the amplifier system configured to generate a pick off voltage signal;

a first low pass filter coupled to the amplifier system and configured to pass a first portion of the pick off voltage signal;

a first proportional-integral-derivative (PID) controller coupled to the first low pass filter, the first PID controller configured to output a Coriolis rebalancing signal based upon the first portion of the pick off voltage signal;

a second low pass filter coupled to the amplifier system and configured to pass a second portion of the pick off voltage signal;

a second PID controller coupled to the second low pass filter, the second PID controller configured to output a quadrature rebalancing signal based upon the second portion of the pick off voltage signal;

a third low pass filter coupled to the amplifier system and configured to pass a third portion of the pick off voltage signal; and

a third PID controller coupled to the third low pass filter, the third PID controller configured to output an acceleration rebalancing signal based upon the third portion of the pick off voltage signal.

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

a means for sensing an out-of-plane linear acceleration of a first proof mass and a second proof mass of the MEMS sensor;

a means for sensing an in-plane rotation of the first proof mass and the second proof mass of the MEMS sensor;

a means for sensing an in-plane linear acceleration of the first proof mass and the second proof mass of the MEMS sensor; and

a means for sensing an out-of-plane rotation of the first proof mass and the second proof mass of the MEMS sensor.

20. The MEMS inertial sensor of claim 19, further comprising:

a means for generating a pick off voltage from the first proof mass and the second proof mass;

a means for generating a Coriolis rebalancing signal from the pick off voltage;

a means for generating a quadrature rebalancing signal from the pick off voltage; and

a means for generating an acceleration rebalancing signal from the pick off voltage.