# US 2013/0152685 A1 · Double-ended tuning fork with outrigger excitation

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- Number: US 2013/0152685 A1
- Document ID: US20130152685A1
- Status: Published application
- Kind: A1
- Application number: 13/331,934
- Filed: 2011-12-20
- Published: 2013-06-20
- Earliest claimed: 2011-12-20
- Assignees: Honeywell International Inc.
- Inventors: Paul W. Dwyer; Arthur Savchenko; Fred Petri
- Web page: https://patentgrep.com/patent/US20130152685A1

## CPC

- G01P 15/097: by vibratory elements
- G01P: MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT (measuring or recording blood flow A61B5/02, A61B8/06; monitoring speed or deceleration of electrically-propelled vehicles B60L3/00; vehicle lighting systems adapted to indicate speed B60Q1/54; determining position or course in navigation, measuring ground distance in geodesy or surveying G01C; combined measuring devices for measuring two or more variables of movement G01C23/00; measuring velocity of sound G01H; measuring velocity of light G01J7/00; measuring direction or velocity of solid objects by reception or emission of radiowaves or other waves and based on propagation effects, e.g. Doppler effect, propagation time, direction of propagation, G01S; measuring speed of nuclear radiation G01T; measuring acceleration of gravity G01V; {measuring or recording the speed of trains B61L23/00; speed indicators incorporated in motor vehicles B60K35/00; measuring frequency or phase G01R; traffic control G08G})

## Abstract

An accelerometer includes a base, a proof mass flexibly connected to the base, and a double-ended tuning fork (DETF) coupled to the proof mass and the base. The DETF includes a base attached to the accelerometer base, an outrigger that extends from a first side of the base, and two tines that extend from a side of the outrigger that is opposite the first side of the base. The accelerometer also includes a drive mechanism that generates opposing forces in different halves of the outrigger, thereby causing the tines to oscillate. An excitation voltage applied to metallized traces on the outrigger at the base of the DETF cause the tines to resonant. The alternating strains generated at the root of the tines excite the tines themselves at their resonant frequency without the requirement of complex metallization applied to the tines.

## Claims

### Claim 1

An accelerometer comprising:
a base;
a proof mass flexibly connected to the base;
a double-ended tuning fork (DETF) coupled to the proof mass and the base, the DETF comprising:
a base attached to the accelerometer base;
an outrigger that extends from a first side of the base; and
two tines that extend from a side of the outrigger that is opposite the first side of the base; and
a drive mechanism configured to cause opposing forces in different halves of the outrigger, thereby causing the tines to oscillate.

### Claim 2 (depends on 1)

The accelerometer of claim 1, wherein the outrigger comprises a piezoelectric material.

### Claim 3 (depends on 1)

The accelerometer of claim 1, wherein the drive mechanism comprises:
a first trace located on an edge face of a first half of the outrigger; and
a second trace located on an edge face of a second half of the outrigger;

### Claim 4 (depends on 3)

The accelerometer of claim 3, wherein the drive mechanism comprises:
a first component coupled to the first trace at a first polarity; and
a second component coupled to the second trace at a second polarity.

### Claim 5 (depends on 1)

The accelerometer of claim 1, wherein the drive mechanism comprises:
a first trace located on a top of a first half of the outrigger;
a second trace located on the top of a second half of the outrigger;
a third trace located on a bottom of the first half of the outrigger;
a fourth trace located on the bottom of the second half of the outrigger;
a fifth trace located on an edge face of a first half of the outrigger; and
a sixth trace located on an edge face of a second half of the outrigger.

### Claim 6 (depends on 5)

The accelerometer of claim 5, wherein the drive mechanism comprises:
a first component coupled to the first, third and sixth traces at a first polarity; and
a second component coupled to the second, fourth and fifth traces at a second polarity.

### Claim 7 (depends on 5)

The accelerometer of claim 5, further comprising:
a first electrical insulator located on the top of the outrigger between the first and second traces.

### Claim 8 (depends on 7)

The accelerometer of claim 7, further comprising:
a second electrical insulator located on the bottom of the outrigger between the third and fourth traces.

### Claim 9 (depends on 1)

The accelerometer of claim 1, wherein the drive mechanism comprises:
a first structure located adjacent to a first edge of the outrigger, the first structure comprising a metalized pad; and
a second structure located adjacent to a second edge of the outrigger, the second structure comprising a metalized pad.

### Claim 10 (depends on 1)

The accelerometer of claim 1, wherein the drive mechanism comprises:
a plurality of structures located adjacent to a top, a bottom and two sides of the outrigger;
a first trace located on a first half of the structure adjacent the top of the outrigger;
a second trace located on a second half of the structure adjacent the top of the outrigger;
a third trace located on a first half of the structure adjacent the bottom of the outrigger;
a fourth trace located on a second half of the structure adjacent the bottom of the outrigger;
a fifth trace located on the structure adjacent the first side of the outrigger;
a sixth trace located on the structure adjacent the second side of the outrigger.

### Claim 11 (depends on 1)

The accelerometer of claim 1, wherein the drive mechanism comprises metalized traces located only on the sides of the outrigger that extends from the first side of the base, a charge applied to the metalized traces is driven at a frequency of twice a desired frequency.

### Claim 12 (depends on 1)

The accelerometer of claim 1, wherein the drive mechanism comprises metalized traces located on surfaces adjacent to the sides of the first outrigger, a charge applied to the metalized traces is driven at a frequency of twice a desired frequency.

### Claim 13

A method comprising:
applying a first electric field across a portion of a first half of an piezoelectric outrigger of a double-ended tuning fork (DETF), the DETF being attached between a base and a proof mass suspended via a flexure from the base;
applying a second electric field across a portion of a second half of the outrigger; and
controlling the applied electric field at a predefined alternating frequency, thereby causing tines of the DETF to oscillate at a resonant frequency.

### Claim 14 (depends on 13)

The method of claim 13, wherein the applied electric field causes parametric driving of the tines.

### Claim 15 (depends on 13)

The method of claim 13, wherein the applied electric field causes non-parametric driving of the tines.

### Claim 16 (depends on 13)

The method of claim 13, wherein the first half of the outrigger comprises:
a first trace located on a top of the outrigger;
a second trace located on a bottom the outrigger; and
a third trace located on an edge face of the outrigger,
wherein the first half of the outrigger comprises:
a second trace located on the top of the outrigger;
a fourth trace located on the bottom of the outrigger; and
a sixth trace located on an edge face of the outrigger.

### Claim 17 (depends on 16)

The method of claim 16, further comprising:
isolating the first electric field from the second electric field.

### Claim 18

A system comprising:
a means for applying a first electric field across a portion of a first half of an piezoelectric outrigger of a double-ended tuning fork (DETF), the DETF being attached between a base and a proof mass suspended via a flexure from the base;
a means for applying a second electric field across a portion of a second half of the outrigger; and
a means for controlling the applied electric field at a predefined alternating frequency, thereby causing tines of the DETF to oscillate at a resonant frequency.

### Claim 19 (depends on 17)

The system of claim 17, wherein the first half of the outrigger comprises:
a first trace on a top of the outrigger;
a second trace on a bottom the outrigger; and
a third trace on an edge face of the outrigger,
wherein the first half of the outrigger comprises:
a second trace on the top of the outrigger;
a fourth trace on the bottom of the outrigger; and
a sixth trace on an edge face of the outrigger.

### Claim 20 (depends on 18)

The system of claim 18, further comprising:
a means for isolating the first electric field from the second electric field.