# US 12,371,157 B2 · Method for monitoring an aircraft landing gear employing at least one accelerometer supported by a wheel of the landing gear, and aircraft implementing this method

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- Number: US 12,371,157 B2
- Document ID: US12371157B2
- Status: Granted
- Kind: B2
- Application number: 18/561,048
- Filed: 2022-05-18
- Published: 2024-08-01
- Granted: 2025-07-29
- Earliest claimed: 2021-05-19
- Assignees: Safran Electronics & Defense; Safran Landing Systems
- Applicants: Safran Electronics & Defense; Safran Landing Systems
- Inventors: Joël Zabulon; Kyril Lekarski; Nicolas Fanton; Benjamin Michaud; Etienne Brunstein
- Web page: https://patentgrep.com/patent/US12371157B2

## CPC

- B60C 23/0488: {Movement sensor, e.g. for sensing angular speed, acceleration or centripetal force}
- B64C 25/28: with indicating or warning devices
- B64C 25/001: {Devices not provided for in the groups B64C25/02 - B64C25/68}
- B64D 2045/008: {Devices for detecting or indicating hard landing}
- B64D 2045/0085: {Devices for aircraft health monitoring, e.g. monitoring flutter or vibration}
- G01B 21/26: for testing wheel alignment
- B60C: VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
- B64C: AEROPLANES; HELICOPTERS
- B64D: EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT
- G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS

## Abstract

A method for monitoring an aircraft landing gear. The method includes using information from at least one accelerometer firmly secured to a landing gear wheel mounted to rotate on a landing gear axle to estimate an angle of deflection α of the axle at least when the wheel is in contact with the ground.

## Claims

### Claim 1

A method of monitoring an aircraft landing gear having a device for monitoring the pressure of a tire, the tire being carried by a wheel of the landing gear, the wheel being mounted to rotate on a landing gear axle, the method comprising:
estimating an angle of deflection α of the axle at least when the wheel is in contact with the ground, wherein the estimation uses information from at least one accelerometer integrated into the pressure monitoring device.

### Claim 2 (depends on 1)

The method according to claim 1, wherein a transverse acceleration γy,c measured by the accelerometer in a direction substantially parallel to a central axis of the axle and dependent on the angle of deflection α of the axle is used to estimate the angle of deflection α of the axle.

### Claim 3 (depends on 2)

The method according to claim 2, wherein an angle β of rotation of the wheel is estimated from an orthoradial acceleration γx,c and/or a radial acceleration γz,c measured by the accelerometer, and a speed of rotation ω=β{dot over ( )} is then estimated, wherein the two estimates are utilized to eliminate from the transverse acceleration γy,c terms varying with the angle of rotation and the speed of rotation, and then the angle of deflection α of the axle is estimated from the transverse acceleration γy,c thus reprocessed.

### Claim 4 (depends on 2)

The method according to claim 2, further comprising filtering the transverse acceleration γy,c and a radial acceleration γz,c measured by the accelerometer to obtain a filtered transverse acceleration γy,c,f and a filtered radial acceleration γz,c,f by eliminating the terms varying periodically as a function of an angle of rotation β of the wheel.

### Claim 5 (depends on 4)

The method according to claim 4, wherein the filtering is started from a landing onset that is detected when the quantity |γz,c| exceeds a threshold or is in saturation.

### Claim 6 (depends on 4)

The method according to claim 4, wherein, after the filtering has been established, the method further comprises:
collecting the data
y
i
=
γ
y
,
c
,
f
(
t
i
)
⁢
h
⁡
(
t
i
)
=
[
1
γ
y
,
c
,
f
⁢
(
t
i
)
]
.
where the ti are the sampling instants, γy,c,f is the filtered transverse acceleration, and γz,c,f is the filtered radial acceleration;
arranging the sampled data into the following matrix form:
Y
=
[
y
1
…
y
n
]
H
=
[
h
1
…
h
n
]
estimating a state vector X by calculating {circumflex over (X)}=M·Y with the pseudo-inverse M=(Ht·H)−1·Ht; and
estimating the angle of deflection of the axle by calculating {circumflex over (α)}=arcsin ({circumflex over (X)}(1)/g) where g is the acceleration of gravity.

### Claim 7 (depends on 6)

The method according to claim 6, wherein the pseudo-inverse calculation is replaced by a recursive least-squares method.

### Claim 8 (depends on 4)

The method according to claim 4, further comprising calculating a corrected acceleration (γy,c,cor) from the filtered accelerations γy,c,f and γz,c,f:
γ
y
,
c
,
cor
≈
γ
y
,
c
,
f
-
θ
y
⁢
z
⁢
γ
z
,
c
,
f
where θyz is given or estimated beforehand, and the angle of deflection of the axle is estimated by the calculation:
α
ˆ
=
arcsin
⁡
(
γ
y
,
c
,
cor
/
g
)
,
where g is the acceleration of gravity.

### Claim 9 (depends on 4)

The method according to claim 4, wherein two accelerometers are used that are arranged on the wheel diametrically opposite each other and measuring respective radial accelerations γz,c,1 and γz,c,2, and wherein the mean radial acceleration
γ
¯
z
,
c
=
γ
z
,
c
,
1
+
γ
z
,
c
,
2
2
is formed and used as the radial acceleration for estimating the deflection angle of the axle.

### Claim 10 (depends on 1)

An aircraft comprising at least one landing gear having a wheel to which is attached at least one accelerometer connected to an electronic control unit performing a computer program comprising instructions arranged to implement the method according to claim 1.