Sensor

• US 9,310,201 B2
• Filed: 09/05/2011
• Issued: 04/12/2016
• Est. Priority Date: 09/17/2010
• Status: Active Grant

• Current Assignee: Atlantic Inertial Systems Incorporated (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: Atlantic Inertial Systems Incorporated (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Fell, Christopher Paul
• Primary Examiner(s): Kwok, Helen
• Application Number:
  US13/823,934
• Publication Number:
  US 20130192368A1
• Time in Patent Office: 1,681 Days
• Field of Search: 735/041.3, 735/041.2, 735/040.4
• US Class Current: 1/1
• CPC Class Codes: G01C 19/5684 the devices involving a micromechanical structure
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis
• CPC Class Codes: Y10T 29/49002 Electrical device making

Abstract

A silicon MEMS gyroscope is described having a ring or hoop-shaped resonator. The resonator is formed by a Deep Reactive Ion Fitch technique and is formed with slots extending around the circumference of the resonator on either side of the neutral axis of the resonator. The slots improve the Quality Factor Q of the gyroscope without affecting the resonant frequency of the resonator.

Claims

1. A sensor having a high Quality Factor (Q) comprising a vibrating structure comprising a substantially planar ring or hoop shaped vibratory resonator, the resonator having inner and outer peripheries extending around a neutral axis, drive means for causing the resonator to vibrate, a plurality of support means for supporting the resonator and for allowing the resonator to vibrate in response to the drive means in a substantially undamped oscillation mode so as to permit the resonator to move relative to the support means in response to turning rate of the sensor, in which the resonator includes a first series of radially positioned slots inwardly of the neutral axis and a second series of radially positioned slots outwardly of the neutral axis of the resonator said first and second series of slots being concentrically positioned relative to the neutral axis of the resonator such that the positioning of the first and second series slots adjusts the thermal relaxation path lengths on the resonator without affecting the resonant frequency of the resonator thereby increasing the Q factor of the resonator, the first and second series of slots being radially positioned on the resonator where the kinetic and strain energy densities are equal such that the effect on the resonator stiffness is approximately equal to the effect on the resonator mass.

2. A sensor according to claim 1 in which the resonator includes a further series of slots positioned inwardly and outwardly of the neutral axis of the resonator.

3. A sensor according to claim 1 in which the first an second series of slots result in the formation of a series of connected thinner ring segments, the length and thickness of the segments being such that the segments are stiffer than the stiffness of the resonator when oscillating in cos 2 θ

mode, the segments substantially behaving as part of a homogeneous structure when the resonator is vibrating in the cos 2 θ

mode.

4. A sensor according to claim 3 in which the arcuate angle of the segments is ≦

5 degrees and the separation between adjacent slots in either series is ≧

2 degrees.

5. A sensor according to claim 1 in which the first and second series of slots are of a uniform design such that the resultant effect on primary and secondary cos 2 θ

mode shapes is equal to avoid any induced imbalance in the frequencies or damping of the resonator.

6. A sensor according to claim 5 in which the first and second series of slots are positioned the same radial distance from neutral axis, have the same angular extent and separation and are equi-angularly positioned around the circumference of the resonator.

7. A sensor according to claim 1 in which the position of the first series of slots inwardly of the neutral axis of the resonator is staggered in relation to the second series of slots outwardly of the neutral axis of the resonator such that a thermal relaxation path length is greater.

8. A method of improving the Quality Factor Q of a sensor having a planar ring or hoop-shaped resonator comprising the step of forming first and second series of slots in the resonator, said first and second series of slots being positioned concentrically, externally and internally to the neutral axis of the resonator such that said slots do not affect the resonant frequency of the resonator, the first and second series of slots being radially positioned on the resonator where the kinetic and strain energy densities are equal such that the effect on the resonator stiffness is approximately equal to the effect on the resonator mass.

9. A method according to claim 8 further comprising the step of forming the first and second series of slots in a uniform design such that the resultant effect on primary and secondary cos 2 θ

mode shapes is equal to avoid any induced imbalance in the frequencies or damping of the resonator.

10. A method according to claim 8 further comprising the step of positioning the first and second series of slots the same radial distance from neutral axis, the slots having the same angular extent and separation and the slots being equi-angularly positioned around the circumference of the resonator.