# US 11,079,227 B2 · Accelerometer system enclosing gas

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- Number: US 11,079,227 B2
- Document ID: US11079227B2
- Status: Granted
- Kind: B2
- Application number: 16/371,657
- Filed: 2019-04-01
- Published: 2020-10-01
- Granted: 2021-08-03
- Earliest claimed: 2019-04-01
- Assignees: Honeywell International Inc.
- Applicants: Honeywell International Inc.
- Inventors: Chad Fertig; Arthur Savchenko; Steven Tin; Neil Krueger; Joshua Dorr
- Web page: https://patentgrep.com/patent/US11079227B2

## CPC

- G01C 19/5614: Signal processing
- G01P 15/093: by photoelectric pick-up
- G01C 19/5621: the devices involving a micromechanical structure
- G01P 15/097: by vibratory elements
- G01P 15/13: by measuring the force required to restore a proofmass subjected to inertial forces to a null position
- G01P 15/18: in two or more dimensions
- G01C: MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY (measuring liquid level G01F; radio navigation, determining distance or velocity by use of propagation effects, e.g. Doppler effects, propagation time, of radio waves, analogous arrangements using other waves G01S)
- 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

This disclosure is related to devices, systems, and techniques for determining, using an electro-opto-mechanical accelerometer system, a frequency value in order to determine an acceleration value. For example, an accelerometer system includes a light-emitting device configured to emit an optical signal and a circuit. The circuit is configured to determine a frequency value corresponding to the optical signal and determine an acceleration value based on the frequency value. Additionally, the accelerometer system includes a housing that encloses the light-emitting device, the circuit, and Helium gas, where the Helium gas defines a partial pressure within a range between 0.1 torr and 760 torr.

## Claims

### Claim 1

An accelerometer system comprising:
a light-emitting device configured to emit an optical signal;
a circuit configured to:
modulate, using a modulating device, the optical signal to produce a modulated optical signal;
receive, using a photoreceiver, the modulated optical signal;
convert, using the photoreceiver, the modulated optical signal into an electrical signal;
process the electrical signal to obtain a processed electrical signal;
transmit the processed electrical signal to the modulating device, wherein the modulating device is configured to modulate the optical signal based on the processed electrical signal;
determine, based on the first processed electrical signal, a frequency value; and
determine an acceleration value based on the frequency value; and
a housing that encloses the light-emitting device, the circuit, and Helium gas, wherein the Helium gas defines a partial pressure within a range between 0.1 torr and 760 torr.

### Claim 2 (depends on 1)

The accelerometer system of claim 1, wherein the housing comprises a crystalline material, the crystalline material preventing the Helium gas from escaping the housing.

### Claim 3 (depends on 2)

The accelerometer system of claim 2, wherein the material comprises silicon.

### Claim 4 (depends on 1)

The accelerometer system of claim 1, wherein the housing comprises:
a first layer comprising an amorphous solid material; and
a second layer comprising a crystalline material, the crystalline material preventing the Helium gas from escaping the housing.

### Claim 5 (depends on 1)

The accelerometer system of claim 1, further comprising:
a first double-ended tuning fork (DETF) structure;
a second DETF structure;
one or more tethers;
a frame; and
a proof mass suspended within the frame by the first DETF structure, the second DETF structure, and the one or more tethers,
wherein the proof mass is suspended in a first direction relative to the frame by the first DETF structure and the second DETF structure,
wherein the first DETF structure contacts a first side of the proof mass and the second DETF structure contacts a second side of the proof mass, the first side being opposite the second side, and
wherein the proof mass is suspended in a second direction and a third direction relative to the frame by the one or more tethers.

### Claim 6 (depends on 5)

The accelerometer system of claim 5, wherein the first direction, the second direction, and the third direction represent three axes (x-axis, y-axis, and z-axis) of a three-dimensional Cartesian space.

### Claim 7 (depends on 5)

The accelerometer system of claim 5, wherein the first DETF structure and the second DETF structure each comprise:
two or more photonic crystal mechanical beams with a gap between the two or more photonic crystal mechanical beams.

### Claim 8 (depends on 5)

The accelerometer system of claim 5, wherein a mechanical quality factor associated with the first DETF structure and the second DETF structure is within a range between 5,000 and 2,000,000.

### Claim 9 (depends on 1)

The accelerometer system of claim 1 wherein the light-emitting device emits the optical signal at a power value, wherein the power value is within a range between 1 nanowatt (nW) and 10,000 nW.

### Claim 10 (depends on 1)

The accelerometer system of claim 1, wherein the modulating device is a first modulating device, the photoreceiver is a first photoreceiver, the modulated optical signal is a first modulated optical signal, the electrical signal is a first electrical signal, the processed electrical signal is a first processed electrical signal, the frequency value is a first frequency value, and wherein the circuit is further configured to:
modulate, using a second modulating device, the optical signal to produce a second modulated optical signal;
receive, using a second photoreceiver, the second modulated optical signal;
convert, using the second photoreceiver, the second modulated optical signal into a second electrical signal;
process the second electrical signal to obtain a second processed electrical signal;
transmit the second processed electrical signal to the second modulating device, wherein the second modulating device is configured to modulate the optical signal based on the second processed electrical signal; and
determine, based on the second processed electrical signal, a second frequency value.

### Claim 11 (depends on 10)

The accelerometer system of claim 10, wherein the acceleration value is a first acceleration value, wherein to determine the first acceleration value, the circuit is configured to:
subtract a baseline frequency value from the first frequency value to obtain a first frequency difference value; and
determine, based on the first frequency difference value, a first acceleration value, and wherein to determine a second acceleration value, the circuit is configured to:
subtract a baseline frequency value from the second frequency value to obtain a second frequency difference value; and
determine, based on the second frequency difference value, a second acceleration value.

### Claim 12

A method comprising:
emitting, using a light-emitting device, an optical signal;
modulating, using a first modulating device of a circuit, the optical signal to produce a first modulated optical signal;
receiving, using a first photoreceiver of the circuit, the first modulated optical signal;
converting, using the first photoreceiver, the first modulated optical signal into a first electrical signal;
processing the first electrical signal to obtain a first processed electrical signal;
transmitting the first processed electrical signal to the first modulating device, wherein the first modulating device is configured to modulate the optical signal based on the processed electrical signal; and
determining, based on the first processed electrical signal, a frequency value;
determining, using the circuit, an acceleration value based on the frequency value; and
enclosing, using a housing, the light-emitting device, the circuit, and Helium gas, wherein the Helium gas defines a partial pressure within a range between 0.1 torr and 760 torr.

### Claim 13 (depends on 12)

The method of claim 12, wherein the housing comprises a crystalline material, the crystalline material preventing the Helium gas from escaping the housing.

### Claim 14 (depends on 12)

The method of claim 12, wherein the housing comprises:
a first layer comprising an amorphous solid material; and
a second layer comprising a crystalline material, the crystalline material preventing the Helium gas from escaping the housing.

### Claim 15 (depends on 12)

The method of claim 12, further comprising:
suspending a proof mass suspended within a frame by a first DETF structure, a second DETF structure, and one or more tethers,
wherein the proof mass is suspended in a first direction relative to the frame by the first DETF structure and the second DETF structure,
wherein the first DETF structure contacts a first side of the proof mass and the second DETF structure contacts a second side of the proof mass, the first side being opposite the second side, and
wherein the proof mass is suspended in a second direction and a third direction relative to the frame by the one or more tethers.

### Claim 16 (depends on 12)

The method of claim 12, wherein the modulating device is a first modulating device, the photoreceiver is a first photoreceiver, the modulated optical signal is a first modulated optical signal, the electrical signal is a first electrical signal, the processed electrical signal is a first processed electrical signal, the frequency value is a first frequency value, and wherein the method further comprises:
modulating, using a second modulating device, the optical signal to produce a second modulated optical signal;
receiving, using a second photoreceiver, the second modulated optical signal;
converting, using the second photoreceiver, the second modulated optical signal into a second electrical signal;
processing the second electrical signal to obtain a second processed electrical signal;
transmitting the second processed electrical signal to the second modulating device, wherein the second modulating device is configured to modulate the optical signal based on the second processed electrical signal; and
determining, based on the second processed electrical signal, a second frequency value.

### Claim 17 (depends on 16)

The method of claim 16, wherein the acceleration value is a first acceleration value, wherein determining the first acceleration value comprises:
subtracting a baseline frequency value from the first frequency value to obtain a first frequency difference value; and
determining, based on the first frequency difference value, a first acceleration value, and wherein the method further comprises:
subtracting a baseline frequency value from the second frequency value to obtain a second frequency difference value; and
determining, based on the second frequency difference value, a second acceleration value.

### Claim 18

An accelerometer system comprising:
a first double-ended tuning fork (DETF) structure;
a second DETF structure;
one or more tethers;
a frame; and
a proof mass suspended within the frame by the first DETF structure, the second DETF structure, and the one or more tethers,
wherein the proof mass is suspended in a first direction relative to the frame by the first DETF structure and the second DETF structure,
wherein the first DETF structure contacts a first side of the proof mass and the second DETF structure contacts a second side of the proof mass, the first side being opposite the second side, and
wherein the proof mass is suspended in a second direction and a third direction relative to the frame by the one or more tethers;
a light-emitting device configured to emit an optical signal;
a circuit configured to:
determine a frequency value corresponding to the optical signal; and
determine an acceleration value based on the frequency value; and
a housing that encloses the light-emitting device, the circuit, and Helium gas, wherein the Helium gas defines a partial pressure within a range between 0.1 torr and 760 torr.