Scale factor measurement for mems gyroscopes and accelerometers

• US 7,726,188 B2
• Filed: 04/24/2007
• Issued: 06/01/2010
• Est. Priority Date: 04/24/2006
• Status: Expired due to Fees

• Current Assignee: Milli Sensor Systems & Actuators, Inc.
• Original Assignee: Milli Sensor Systems & Actuators, Inc.
• Inventors: Cardarelli, Donato
• Primary Examiner(s): Kwok; Helen C.
• Application Number:
  US11/739,455
• Publication Number:
  US 20100024548A1
• Time in Patent Office: 1,134 Days
• Field of Search: 735/040.4, 735/041.2, 735/040.3, 735/041.3, 735/141.5, 735/141.8, 735/143.8
• US Class Current: 73/504.13
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/097 by vibratory elements
• CPC Class Codes: G01P 2015/0814 for translational movement of the mass, e.g. shuttle type

Abstract

An inertial instrument such as an accelerometer or gyroscope having scale factor functionality, and that lies generally in a plane. The gyro detects rotation rate about a gyro input axis. The gyroscope has a substrate, a generally planar scale factor gimbal flexibly coupled to the substrate such that it is capable of oscillatory motion about the input axis, a generally planar support member coplanar with and flexibly coupled to the scale factor gimbal such that the support member is capable of oscillatory motion about a drive axis that is orthogonal to the input axis, and a generally planar gyro member coplanar with and flexibly coupled to the support member such that it is capable of rotary oscillatory motion relative to the support member about an output axis that is orthogonal to the plane of the members. There are one or more first drives for oscillating the support member about the drive axis, and one or more second drives for oscillating the scale factor gimbal about the input axis. One or more gyro output sensors that detect oscillation of the gyro member about an output axis that is orthogonal to both the input axis and the drive axis.

Claims

1. A gyroscope that lies generally in a plane, for detecting rotation rate about a gyro input axis, the gyroscope having scale factor functionality, comprising:

a substrate;

a generally planar scale factor gimbal flexibly coupled to the substrate such that the scale factor gimbal is capable of oscillatory motion about the input axis;

a generally planar support member coplanar with and flexibly coupled to the scale factor gimbal such that the support member is capable of oscillatory motion about a drive axis that is orthogonal to the input axis;

a generally planar gyro member coplanar with and flexibly coupled to the support member such that the gyro member is capable of rotary oscillatory motion relative to the support member about an output axis that is orthogonal to the plane of the support and gyro members;

one or more first drives for oscillating the support member about the drive axis;

one or more second drives for oscillating the scale factor gimbal about the input axis; and

one or more gyro output sensors that detect oscillation of the gyro member about an output axis that is orthogonal to both the input axis and the drive axis.

2. The gyroscope of claim 1 in which the first and second drives comprise capacitive drives.

3. The gyroscope of claim 2 in which the first and second drives comprise plates.

4. The gyroscope of claim 1 in which there is at least one first drive on each side of the drive axis and at least one second drive on each side of the input axis.

5. The gyroscope of claim 1 in which the gyro output sensors comprise capacitive sensors.

6. The gyroscope of claim 5 in which the gyro output sensors comprise comb sensors.

7. The gyroscope of claim 6 in which the comb sensors comprise sectors that are radially arranged around the output axis.

8. The gyroscope of claim 7 comprising two pairs of diametrically opposed comb sensor sectors, with the signals from the pairs differenced, to increase the signal strength and reduce common-mode noise.

9. The gyroscope of claim 1 further comprising one or more support member motion sensors that sense motion of the support member about the drive axis.

10. The gyroscope of claim 9 in which the support member motion sensors comprise capacitive plate sensors.

11. The gyroscope of claim 9 further comprising one or more scale factor gimbal motion sensors that sense motion of the scale factor gimbal about the input axis.

12. The gyroscope of claim 11 in which the scale factor gimbal motion sensors comprise capacitive plate sensors.

13. The gyroscope of claim 11 further comprising a controller, responsive to the support member motion sensors, for maintaining an oscillation amplitude of the support member constant.

14. The gyroscope of claim 11 further comprising a controller, responsive to the scale factor gimbal sensors, for maintaining an oscillation amplitude of the scale factor gimbal constant.

15. The gyroscope of claim 1 in which the gyro member is flexibly coupled to the support member by a plurality of gyro member flexures.

16. The gyroscope of claim 15 in which the gyro member flexures each comprise two bending “

U”

flexures.

17. The gyroscope of claim 1 in which the support and gyro members are both generally annular.

18. The gyroscope of claim 1 in which the support member is flexibly coupled to the scale factor gimbal by a pair of linear flexures.

19. The gyroscope of claim 1 in which the gyro member is located within the support member.

20. The gyroscope of claim 19 in which the gyro member is coupled to the support member by flexures that are generally radial relative to the output axis.

21. A linear accelerometer with integral scale factor functionality, the accelerometer lying generally in a plane, for detecting acceleration along an acceleration input axis that lies in the plane, comprising:

a substrate defining a surface;

spaced bonding pads coupled to the substrate and projecting from the surface of the substrate;

a shuttle spaced from the surface of the substrate and flexibly coupled to the bonding pads by shuttle flexures, such that the shuttle is capable of linear oscillatory motion relative to the substrate parallel to the input axis;

a linear accelerometer located within and flexibly coupled to the shuttle by flexures such that the linear accelerometer is capable of motion along the input axis relative to the shuttle;

one or more shuttle drives that oscillate the shuttle parallel to the input axis at a shuttle oscillation frequency, and thereby also oscillate the linear accelerometer along the input axis at the shuttle oscillation frequency;

one or more shuttle oscillation sensors that determine the amplitude of the shuttle oscillation; and

one or more accelerometer motion sensors that determine the accelerometer motion that is caused by both the shuttle oscillatory displacement due to the shuttle drives and any acceleration along the input axis.