Micromechanical inertial sensor having increased pickoff resonance damping

• US 6,598,475 B2
• Filed: 09/20/2001
• Issued: 07/29/2003
• Est. Priority Date: 09/20/2001
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Pinson, John C.
• Primary Examiner(s): KWOK, HELEN C
• Application Number:
  US09/957,425
• Publication Number:
  US 20030061878A1
• Time in Patent Office: 677 Days
• Field of Search: 735/040.2, 735/040.4, 735/041.2, 735/041.3, 735/041.4, 735/041.5, 735/041.6, 735/143.2, 735/142.9, 735/141.5, 735/141.6, 310/329, 310/370
• US Class Current: 73/504.12
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis

Abstract

A micromechanical inertial sensor is provided having a reduced pickoff Q, while maintaining a high motor Q. The micromechanical inertial sensor includes a pair of proof masses and aligned pickoff plates. Each pickoff plate is spaced from the respective proof mass by a gap that varies in response to out-of-plane movement of the proof mass. The micromechanical inertial sensor also includes at least one voltage source for providing charge to the pickoff plates. By measuring the movement of charge in each electrical circuit that includes a pickoff plate as the gap between the pickoff plate and the respective proof mass varies, a measurement of the rotation of the micromechanical inertial sensor about an input axis may be obtained. The micromechanical inertial sensor further includes resistive elements disposed in series between the voltage source and each pickoff plate to increase the pickoff resonance damping of the micromechanical inertial sensor.

Claims

1. A micromechanical inertial sensor adapted to sense rotation about a first axis, the micromechanical inertial sensor comprising:

a substrate;

first and second proof masses spaced apart from and mechanically connected to said substrate, said proof masses adapted to vibrate along a second axis substantially orthogonal to the first axis, said proof masses also being movable along a third axis substantially orthogonal to the first and second axes;

a plurality of pickoff plates in at least partial alignment with respective proof masses, said pickoff plates spaced from said proof masses by a gap that varies in response to movement of said proof masses along the third axis;

at least one voltage source electrically connected to said pickoff plates; and

a plurality of resistive elements disposed in series between the at least one voltage source and respective pickoff plates to reduce pickoff resonance of the micromechanical inertial sensor.

2. A micromechanical inertial sensor according to claim 1 wherein each resistive element is sized to between 10 kiloohms and 10 megohms.

3. A micromechanical inertial sensor according to claim 2 wherein each resistive element is sized to be 1 megohm.

4. A micromechanical inertial sensor according to claim 1 wherein each resistive element is selected such that the pickoff resonance has a Q of no more than 1000.

5. A micromechanical inertial sensor according to claim 1 further comprising a plurality of drive electrodes, wherein each proof mass carries a plurality of driven electrodes that are interdigitated with said drive electrodes such that electrical stimuli applied to said drive electrodes induces vibration of the respective proof mass along the second axis.

6. A micromechanical tuning fork gyroscope adapted to sense rotation about a first axis, the micromechanical tuning fork gyroscope comprising:

first and second proof masses operably connected to mechanical ground and adapted to vibrate along a second axis substantially orthogonal to the first axis, said proof masses also being movable along a third axis substantially orthogonal to the first and second axes in response to rotation about the first axis;

a plurality of pickoff plates in at least partial alignment with respective proof masses and capacitively coupled thereto such that capacitance established between said pickoff plates and said proof masses provides a measure of movement of said proof masses along the third axis;

at least one voltage source electrically connected to said pickoff plates; and

a plurality of resistive elements disposed in series between said at least one voltage source and respective pickoff plates to increase pickoff resonance damping of the micromechanical tuning fork gyroscope.

7. A micromechanical tuning fork gyroscope according to claim 6 wherein each resistive element is sized to between 10 kiloohms and 10 megohms.

8. A micromechanical tuning fork gyroscope according to claim 7 wherein each resistive element is sized to be 1 megohm.

9. A micromechanical tuning fork gyroscope according to claim 6 wherein the plurality of resistive elements also reduce pickoff resonance of the micromechanical tuning fork gyroscope, and wherein each resistive element is selected such that the pickoff resonance has a Q of no more than 1000.

10. A micromechanical tuning fork gyroscope according to claim 6 further comprising a plurality of drive electrodes, wherein each proof mass carries a plurality of driven electrodes that are interdigitated with said drive electrodes such that electrical stimuli applied to said drive electrodes induces vibration of the respective proof mass along the second axis.

11. A micromechanical inertial sensor adapted to sense rotation about a first axis, the micromechanical inertial sensor comprising:

a substrate;

first and second proof masses spaced apart from and mechanically connected to said substrate, said proof masses adapted to vibrate along a second axis substantially orthogonal to the first axis, said proof masses also being movable along a third axis substantially orthogonal to the first and second axes in response to rotation about the first axis;

a plurality of pickoff plates disposed upon said substrate in at least partial alignment with respective proof masses, said pickoff plates spaced from said proof masses by a gap that varies in response to movement of said proof masses along the third axis;

at least one voltage source electrically connected to said pickoff plates; and

a plurality of resistive elements disposed in series between the at least one voltage source and respective pickoff plates, said resistive elements being sized between 10 kiloohms and 10 megohms.

12. A micromechanical inertial sensor according to claim 11 wherein each resistive element is sized to be 1 megohm.

13. A micromechanical inertial sensor according to claim 11 wherein the plurality of resistive elements also reduce pickoff resonance of the micromechanical tuning fork gyroscope, and wherein each resistive element is selected such that the pickoff resonance has a Q of no more than 1000.

14. A micromechanical inertial sensor according to claim 11 further comprising a plurality of drive electrodes, wherein each proof mass carries a plurality of driven electrodes that are interdigitated with said drive electrodes such that electrical stimuli applied to said drive electrodes induces vibration of the respective proof mass along the second axis.