# US 2021/0239731 A1 · Method for calibrating a radial-acceleration sensor for the wheel of a motor vehicle

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- Number: US 2021/0239731 A1
- Document ID: US20210239731A1
- Status: Published application
- Kind: A1
- Application number: 17/264,138
- Filed: 2019-07-16
- Published: 2021-08-05
- Earliest claimed: 2018-07-30
- Assignees: Continental Automotive France; Continental Automotive GmbH
- Applicants: Continental Automotive France; Continental Automotive GmbH
- Inventors: Nicolas Guinart; Sébastien Plancke; Jean-Philippe Boisset
- Web page: https://patentgrep.com/patent/US20210239731A1

## CPC

- G01P 21/00: Testing or calibrating of apparatus or devices covered by the preceding groups
- B60C 23/0488: {Movement sensor, e.g. for sensing angular speed, acceleration or centripetal force}
- B60C 23/0489: {for detecting the actual angular position of the monitoring device while the wheel is turning}
- G01L 17/00: Devices or apparatus for measuring tyre pressure or the pressure in other inflated bodies
- G01P 1/00: Details of instruments
- G01P 3/48: by measuring frequency of generated current or voltage {(in general G01R23/00)}
- G01P 15/09: by piezoelectric pick-up
- 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})
- B60C: VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
- G01L: MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE (weighing G01G)

## Abstract

A method for calibrating a radial acceleration sensor of a wheel of a vehicle including the following steps: acquisition, by the sensor, of signals Si, each signal Si being acquired during a predetermined time window Wi when the vehicle is in motion, the windows Wi being different from one another; detection, for each time window Wi, of local extrema of the signal Si associated respectively with phase values and detection instants; determination, for each time window Wi, of a frequency Fi of the rotation of the wheel of the vehicle as a function of the phase values and of the detection instants for the local extrema detected; low-pass filtering of the signals Si, so as to obtain, for each time window Wi, a filtered value Zi; calibration of a constant error Ec of the radial acceleration sensor as a function of the filtered values Zi and of the frequencies Fi.

## Claims

### Claim 1

A method for calibrating a radial acceleration sensor of a wheel of a motor vehicle, said method comprising:
an acquisition step of acquisition, by the radial acceleration sensor, of signals Si, each signal Si being acquired during a predetermined time window Wi when the vehicle is in motion, the windows Wi being different from one another,
a detection step of detecting, for each time window Wi, at least three local extrema of the signal Si which are respectively associated with phase values and with detection instants,
a determination step of determining, for each time window Wi, a frequency Fi of the rotation of the wheel of the vehicle as a function of the phase values and of the detection instants for the local extrema detected in said time window Wi,
a filtering step of low-pass filtering of the signals Si, so as to obtain, for each time window Wi, a filtered value Zi associated with the frequency Fi, and
a calibration step of calibrating a constant error Ec of the radial acceleration sensor as a function of the filtered values Zi and of the frequencies Fi.

### Claim 2 (depends on 1)

The method as claimed in claim 1, wherein the step of determining the frequency Fi comprises, for each time window Wi considered, determining a phase time signal φi by quadratic interpolation of the respective phase values of three local extrema, the frequency Fi being determined by evaluating the derivative of said signal φi with respect to time at a predetermined instant tp within said time window Wi.

### Claim 3 (depends on 2)

The method as claimed in claim 2, wherein the three local extrema considered within each time window Wi are consecutive.

### Claim 4 (depends on 1)

The method as claimed in claim 1, wherein the cut-off frequency of the low-pass filter applied to the signals Si is less than or equal to 10 Hz, preferably less than 5 Hz, and more preferably still equal to 1 Hz.

### Claim 5 (depends on 1)

The method as claimed in claim 1, wherein the step of calibrating the constant error Ec comprises a linear regression of points Pi, each point Pi having Zi and Fi2 as its ordinate and abscissa values respectively, the constant error Ec being estimated to be equal to the ordinate value at the origin of said linear regression.

### Claim 6 (depends on 1)

The method as claimed in claim 1, said method comprising, after the detection step, a step 600 of estimating, for at least one time window Wi, an error Ri in the gain of the radial acceleration sensor according to the formula: Ri=Vi/Qi, where Vi represents an amplitude associated with at least one local extremum of the signal Si acquired during said at least one time window Wi, and Qi represents an amplitude that is expected on the basis of measurements theoretically supplied by the radial acceleration sensor for said at least one local extremum, the gain error Ri being calculated only if a steady-speed phase is detected for the signal Si.

### Claim 7 (depends on 6)

The method as claimed in claim 6, wherein, the step of determining the frequency Fi comprises, for each time window Wi considered, determining a phase time signal φi by quadratic interpolation of the respective phase values of three local extrema, the frequency Fi being determined by evaluating the derivative of said signal φi with respect to time at a redetermined instant tp within said time window Wi, and the step of estimating a gain error comprises, for each time window Wi, making the comparison between the second derivative of the phase time signal φi and a predetermined value ε, such that if |d2φi/dt2|<ε, a steady-speed phase is detected.

### Claim 8 (depends on 6)

The method as claimed in claim 6, wherein the amplitude Vi corresponds to the amplitude between two consecutive local extrema of the signal Si in a steady-speed phase, and Qi satisfies:
Qi=2×g×G,
where g is the acceleration due to gravity, and G represents the gain of a filter applied to the signal Si during the detection step (200) so as to reduce measurement noise.

### Claim 9 (depends on 1)

A wheel unit comprising a radial acceleration sensor, said wheel unit comprising means configured for implementing the steps of the calibration method as claimed in claim 1 so as to calibrate said radial acceleration sensor.

### Claim 10 (depends on 9)

A motor vehicle comprising a wheel unit as claimed in claim 9.

### Claim 11 (depends on 7)

The method as claimed in claim 7, wherein the amplitude Vi corresponds to the amplitude between two consecutive local extrema of the signal Si in a steady-speed phase, and Qi satisfies:
Qi=2×g×G,
where g is the acceleration due to gravity, and G represents the gain of a filter applied to the signal Si during the detection step (200) so as to reduce measurement noise.