Micro-electro-mechanical gyroscope

• US 6,516,665 B1
• Filed: 06/15/2000
• Issued: 02/11/2003
• Est. Priority Date: 06/17/1999
• Status: Expired due to Fees

• Current Assignee: Penn State Research Foundation
• Original Assignee: Penn State Research Foundation
• Inventors: Varadan, Vijay K., Xavier, Pascal B., Suh, William D., Kollakompil, Jose A., Varadan, Vasundara V.
• Primary Examiner(s): KWOK, HELEN C
• Application Number:
  US09/594,370
• Time in Patent Office: 971 Days
• Field of Search: 735/040.1, 735/040.2, 735/142.8, 310/311, 310/313.A, 310/313.B, 310/313.D, 310/313.R
• US Class Current: 73/504.01
• CPC Class Codes: G01C 19/5698 using acoustic waves, e.g. surface acoustic wave gyros
• CPC Class Codes: H03H 9/02645 Waffle-iron or dot arrays
• CPC Class Codes: H03H 9/6486 having crossing or intersecting acoustic tracks, e.g. intersection in a perpendicular or diagonal orientation

Abstract

A gyroscope comprises a piezoelectric substrate having a surface. Disposed on the surface are a resonator transducer, a pair of reflectors, a structure such as a metallic dot, and a sensor transducer. The resonator transducer creates a first surface acoustic wave on the surface. The pair of reflectors reflects the first surface acoustic wave to form a standing wave within a region of the surface between the pair of reflectors. The structure is disposed on the surface within the region, wherein a Coriolis force acting upon the structure creates a second surface acoustic wave. The sensor senses the second surface acoustic wave and provides an output indicative thereof.

Claims

1. A gyroscope comprising:

a substrate having a surface, said substrate being comprised of piezoelectric material;

a resonator transducer disposed on said surface, for creating a first surface acoustic wave on said surface;

a pair of reflectors disposed on said surface, for reflecting said first surface acoustic wave to form a standing wave within a first region of said surface between said pair of reflectors;

a structure disposed on said surface within said first region, wherein a Coriolis force acting upon said structure creates a second surface acoustic wave;

a first sensor transducer disposed on said surface for sensing said second surface acoustic wave and providing an output indicative thereof,

a second sensor transducer disposed on said surface for sensing a residual surface acoustic wave from a second region of said surface that is free of any structure that said Coriolis force can act upon, and for providing an output indicative of said residual surface acoustic wave, and

wherein a difference between said output of said first sensor transducer and said output of said second sensor transducer is processed to characterize said Coriolis force.

2. The gyroscope of claim 1, wherein said first and second sensor transducers are disposed orthogonally to said resonator transducer.

3. The gyroscope of claim 1, wherein said resonator transducer creates an electrical potential on said substrate, and said substrate converts said electrical potential into mechanical energy, thus forming said first surface acoustic wave.

4. The gyroscope of claim 1, wherein said structure is located at an anti-node of said standing wave.

5. The gyroscope of claim 1,

wherein said first surface acoustic wave causes said structure to oscillate along a z-axis, and

wherein said Coriolis force is directed along a y-axis and is related to a rate of rotation of said substrate about an x-axis.

6. The gyroscope of claim 1,

wherein said structure is one of a plurality of structures disposed in an array within said first region,

wherein said first surface acoustic wave causes said plurality of structures to oscillate along a z-axis, and

wherein said Coriolis force is directed along a y-axis and is related to a rate of rotation of said substrate about an x-axis.

7. The gyroscope of claim 6, wherein said x-axis and said y-axis comprise an x-y plane, and wherein said array is located in said x-y plane such that said Coriolis force, acting upon each of said plurality of structures, creates a plurality of said second surface acoustic wave that are coherently added.

8. The gyroscope of claim 6, wherein said first surface acoustic wave has a wavelength, and wherein said plurality of structures are spaced apart from one another with a periodicity of said wavelength.

9. The gyroscope of claim 6, wherein said second surface acoustic wave has a wavelength, and wherein said plurality of structures are spaced apart from one another with a periodicity of said wavelength.

10. The gyroscope of claim 1, wherein said substrate comprises a material selected from the group consisting of lithium niobate, lithium tantalate, lithium tetraborate, quartz and combinations thereof.

11. The gyroscope of claim 1, wherein said first surface acoustic wave has a wavelength, and wherein said resonator transducer comprises an inter-digital transducer (IDT) comprising fingers spaced apart with a periodicity of one half said wavelength.

12. The gyroscope of claim 1, wherein said first surface acoustic wave has a wavelength, and wherein said pair of reflectors are separated from each other by a distance of an integral number of one half said wavelength.

13. The gyroscope of claim 1, wherein said resonator transducer receives an RF signal that initiates an oscillation of said resonator transducer.

14. The gyroscope of claim 13,

wherein said RF signal is coupled from an antenna to a first port of a duplexer, and thereafter from a second port of said duplexer to said resonator transducer, and

wherein said output of said sensor transducer is coupled to a third port of said duplexer, and thereafter from said first port of said duplexer to said antenna.

15. The gyroscope of claim 1, wherein said first surface acoustic wave has a frequency in the range of 1 MHz to 5 GHz.

16. The gyroscope of claim 1, further comprising:

a third sensor transducer disposed on said surface orthogonally to said resonator transducer and separated from said first sensor transducer by said first region, for sensing said second surface acoustic wave and providing an output indicative thereof; and

a fourth sensor transducer disposed on said surface orthogonally to said resonator transducer and separated from said second sensor transducer by said second region, for sensing said residual surface acoustic wave and providing an output indicative thereof,

wherein said output of said first and third sensor transducers are added to provide a combined output indicative of said second surface acoustic wave,

wherein said output of said second and fourth sensor transducers are added to provide a combined output indicative of said residual surface acoustic wave, and

wherein a difference between said combined output indicative of said second surface acoustic wave and said combined output indicative of said residual surface acoustic wave is processed to characterize said Coriolis force.

17. The gyroscope of claim 1,

wherein said structure has a first dimension in a direction of said first surface acoustic wave and a second dimension in a direction of said second surface acoustic wave, and

wherein said first dimension is different from said second dimension.

18. The gyroscope of claim 1,

wherein said structure is one of a plurality of structures disposed in an array within said region,

wherein said plurality of structures have a first spacing in a direction of said first surface acoustic wave and a second spacing in a direction of said second surface acoustic wave, and

wherein said first spacing is different from said second spacing.

19. The gyroscope of claim 1, wherein said output of said second sensor transducer is a reference signal, said output signal of said first sensor transducer is a test signal, and further comprising a differential amplifier for subtracting the reference signal from the test signal to minimize the effect of noise.

20. The gyroscope of claim 1, further comprising an antenna for receiving a first signal from an external transmitter for initiating said first surface acoustic wave, and for transmitting a second signal derived from said difference between said output of said first sensor transducer and said output of said second sensor transducer to an external receiver.

21. A gyroscope comprising:

a substrate having a surface, said substrate being comprised of piezoelectric material;

a first resonator transducer disposed on said surface, for creating a first surface acoustic wave on said surface;

a pair of reflectors disposed on said surface, for reflecting said first surface acoustic wave to form a standing wave within a first region of said surface between said pair of reflectors;

a structure disposed on said surface within said first region, wherein a Coriolis force acting upon said structure creates a second surface acoustic wave;

a first sensor transducer disposed on said surface for sensing said second surface acoustic wave and providing an output indicative thereof,

a second resonator transducer disposed on said surface for creating a third surface acoustic wave on said surface;

a second pair of reflectors disposed on said surface for reflecting said third surface acoustic wave to form a second standing wave within a second region of said surface between said second pair of reflectors, wherein said second region is free of any structure that said Coriolis force can act upon; and

a second sensor transducer disposed on said surface for sensing a residual surface acoustic wave from said second region, and providing an output indicative thereof;

wherein a difference between said output of said first sensor transducer and said second sensor transducer is processed to characterize said Coriolis force.

22. A gyroscope comprising:

a piezoelectric substrate having a surface;

a resonator disposed on said surface for creating a first surface acoustic wave within a region of said surface;

a structure disposed on said surface within said region for oscillating in response to said first surface acoustic wave, wherein a Coriolis force acting upon said structure creates a second surface acoustic wave;

a sensor disposed on said surface for sensing said second surface acoustic wave and providing an output indicative thereof; and

an antenna for receiving a first signal from an external transmitter for initiating an oscillation of said resonator, and for transmitting a second signal derived from said output of said sensor to an external receiver.