ELECTRIC GRADIENT FORCE DRIVE AND SENSE MECHANISM FOR A MICRO-ELECTRO-MECHANICAL-SYSTEM GYROSCOPE

• US 20150000401A1
• Filed: 06/28/2013
• Published: 01/01/2015
• Est. Priority Date: 06/28/2013
• Status: Active Grant

• Current Assignee: HRL Laboratories LLC (The Boeing Co.)
• Original Assignee: HRL Laboratories LLC (The Boeing Co.)
• Inventors: Nguyen, Hung, Kirby, Deborah J., Chang, David T., Perahia, Raviv, Iyer, Srikanth S.
• Granted Patent: US 9,404,748 B2
• Time in Patent Office: Days
• US Class Current: 73/504.12
• CPC Class Codes: G01C 19/5726 Signal processing
• CPC Class Codes: G01C 19/5755 the devices having a single sensing mass
• CPC Class Codes: G01P 15/125 by capacitive pick-up

Abstract

An apparatus for driving and sensing motion in a gyroscope including a dielectric mass, an anchor, a spring coupled between the anchor and the dielectric mass, a substrate adjacent the dielectric mass, an insulator layer on the substrate, and a first electrode and a second electrode on the insulator layer. When an alternating current voltage is applied between the first and second electrodes, an electric field gradient is generated in the dielectric mass and causes the dielectric mass to move relative to the anchor. When the dielectric mass has motion relative to the anchor and a voltage is applied between the first and second electrodes, the movement of the dielectric mass generates a current at the first and second electrodes proportional to the motion.

Claims

1. An apparatus for driving and sensing motion in a gyroscope comprising:

a dielectric mass;

an anchor;

a spring coupled between the anchor and the dielectric mass;

a substrate adjacent the dielectric mass;

an insulator layer on the substrate; and

a first electrode and a second electrode on the insulator layer;

wherein when an alternating current voltage is applied between the first and second electrodes, an electric field gradient is generated in the dielectric mass and causes the dielectric mass to move relative to the anchor; and

wherein when the dielectric mass has motion relative to the anchor and a voltage is applied between the first and second electrodes, the movement of the dielectric mass generates a current at the first and second electrodes proportional to the motion.

2. The apparatus of claim 1 further comprising a dielectric layer covering the first and second electrodes to increase a breakdown voltage between the first and second electrodes.

3. The apparatus of claim 1 wherein the gyroscope is a micro-electrical mechanical systems gyroscope.

4. The apparatus of claim 1 wherein the alternating current voltage applied between the first and second electrodes has a frequency matching or near a resonant frequency of a mechanical resonator comprising the dielectric mass, the anchor, and the spring.

5. The apparatus of claim 1 wherein the first and second electrodes are coupled to a low noise amplifier to increase sensitivity.

6. A gyroscope for sensing a rotation rate about a z axis comprising:

a mass spring system comprising;

a dielectric mass;

a first anchor oriented in an x axis normal to the z axis;

a first spring coupled between the first anchor and the dielectric mass;

a second anchor oriented in a y direction orthogonal to the z axis and the x axis; and

a second spring coupled between the second anchor and the dielectric mass;

a first substrate adjacent the dielectric mass in the x direction opposite the first anchor;

a first insulator layer on the first substrate; and

a first electrode and a second electrode on the first insulator layer;

a second substrate adjacent the dielectric mass in the y direction opposite the second anchor;

a second insulator layer on the second substrate; and

a third electrode and a fourth electrode on the second insulator layer;

wherein when an alternating current voltage is applied between the first and second electrodes, an electric field gradient is generated in the dielectric mass and causes the dielectric mass to move relative to the first and second anchors; and

wherein when a voltage is applied between the third and fourth electrodes, the movement of the dielectric mass generates a current at the third and fourth electrodes proportional to the motion.

7. The apparatus of claim 6 further comprising:

a first dielectric layer covering the first and second electrodes to increase a breakdown voltage between the first and second electrodes; and

a third dielectric layer covering the third and fourth electrodes to increase a breakdown voltage between the third and fourth electrodes.

8. The apparatus of claim 6 wherein the gyroscope is a micro-electrical mechanical systems gyroscope.

9. The apparatus of claim 6 wherein the alternating current voltage applied between the first and second electrodes has a frequency matching or near a resonant frequency of a mechanical resonator comprising the dielectric mass, the anchor, and the spring.

10. A micro-electrical mechanical systems (MEMS) gyroscope comprising:

a dielectric micro-shell;

a first set of drivers comprising;

a first driver on a side of a periphery of the dielectric micro-shell; and

a second driver on a side of the periphery of the dielectric micro-shell opposite the first driver;

a first set of sensors placed 45°

rotated from the first set of drivers comprising;

a first sensor on one side of the periphery of the dielectric micro-shell; and

a second sensor on a side of the periphery of the dielectric micro-shell opposite the first sensor;

wherein each driver is actuated by an alternating current voltage between electrodes in the driver;

wherein the first driver and the second driver are driven out of phase with each other to excite a wineglass vibrational mode in the dielectric micro-shell;

wherein each sensor senses motion in the dielectric micro-shell by applying a voltage to electrodes in the sensor and sensing current generated from the electrodes by the vibration of the dielectric micro-shell;

wherein the drivers and sensors are not on the micro-shell; and

wherein the resonant frequency of the micro-shell ranges from 10 KHz to 500 KHz.

11. The MEMS gyroscope of claim 10 further comprising:

a second set of drivers located at a 90 degree rotation along the periphery of the dielectric micro-shell from the first set of drivers comprising;

a third driver on one side of the periphery of the dielectric micro-shell; and

a fourth driver on a side of the periphery of the dielectric micro-shell opposite the third driver; and

a second set of sensors located at a 90 degree rotation along the periphery of the dielectric micro-shell from the first set of sensors comprising;

a third sensor on one side of the periphery of the dielectric micro-shell; and

a fourth sensor on a side of the periphery of the dielectric micro-shell opposite the third sensor.

12. The MEMS gyroscope of claim 11 wherein:

a plurality of drivers are at each location for a driver to increase a drive force; and

a plurality of sensors are at each location for a sensor to increase sensitivity.

13. The MEMS gyroscope of claim 11 further comprising:

a support structure adjacent the periphery of the dielectric micro-shell for supporting the electrodes for each driver and sensor;

an insulator on the support structure;

wherein the electrodes for each driver and sensor are on the insulator on a face of the support structure that faces the dielectric micro-shell.

14. The MEMS gyroscope of claim 13 wherein:

a distance between the dielectric micro-shell and the drivers or sensors ranges between 100s of nanometers to 10s of microns.

15. The MEMS gyroscope of claim 11 wherein:

voltages at the electrodes of the drivers and sensors range between 0 volts and +100 volts or −

100 volts.

16. The MEMS gyroscope of claim 11 wherein:

a size of each driver ranges from microns to millimeters; and

a size of each sensor ranges from microns to millimeters.

17. The MEMS gyroscope of claim 13 wherein:

the support structure is vertical, angled, curved, or has a complex topography relative to the periphery of the dielectric micro-shell to increase the drive force and sense sensitivity; and

the electrodes are vertical, horizontal, flat, angled or curved.

18. The MEMS gyroscope of claim 13 wherein:

the support structure is flat, curved, or has a complex topography in a circumferential direction relative to the periphery of the dielectric micro-shell to optimize the drive force and sense sensitivity; and

the electrodes are vertical, horizontal, flat, angled or curved.

19. The MEMS gyroscope of claim 11 wherein electrodes in each driver are covered by a dielectric layer in order to increase a breakdown voltage between two adjacent electrodes.

20. The MEMS gyroscope of claim 11 further comprising:

a support structure adjacent the periphery of the dielectric micro-shell for supporting the electrodes for each driver and sensor;

an insulator on top of the support structure;

wherein the electrodes for each driver and sensor are on the insulator.

21. The MEMS gyroscope of claim 20 wherein electrodes arranged on top of the support structure are arranged in a horizontal plane around the periphery of the dielectric micro-shell with a separation between adjacent drivers and/or sensors.

22. The MEMS gyroscope of claim 10:

wherein a diameter of the micro-shell ranges from lOs of microns to several millimeters;

wherein walls of the micro-shell have thickness that ranges from 100s of nanometers to lOs of microns; and

wherein a height of the micro-shell ranges from a few microns to 1 millimeter.

23. A gyroscope comprising:

a dielectric mass;

a driver adjacent the dielectric mass, the driver configured to generate an electrical gradient force drive that extends into the dielectric mass; and

a sensor adjacent the dielectric mass, the sensor configured to sense movement in the dielectric mass by sensing a change of the field in the dielectric mass.