METHOD FOR DETERMINING A WHEEL TIRE GROUND PRINT

• US 20160303928A1
• Filed: 11/24/2014
• Published: 10/20/2016
• Est. Priority Date: 12/05/2013
• Status: Active Grant

• Current Assignee: Continental Automotive France (Continental AG), Continental Automotive GmbH (Continental AG)
• Original Assignee: Continental Automotive France (Continental AG), Continental Automotive GmbH (Continental AG)
• Inventors: BENBOUHOUT, Rachid, BOUTHINON, Jean-Christophe
• Granted Patent: US 10,207,551 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B60C 2019/004 Tyre sensors other than for detecting tyre pressure
• CPC Class Codes: B60C 23/0408 transmitting the signals by non-mechanical means from the wheel or tyre to a vehicle body mounted receiver
• CPC Class Codes: B60C 23/0447 Wheel or tyre mounted circuits
• CPC Class Codes: B60C 23/0474 Measurement control, e.g. setting measurement rate or calibrating of sensors; Further processing of measured values, e.g. filtering, compensating or slope monitoring
• CPC Class Codes: B60C 23/0488 Movement sensor, e.g. for sensing angular speed, acceleration or centripetal force
• CPC Class Codes: B60C 23/064 comprising tyre mounted deformation sensors, e.g. to determine road contact area
• CPC Class Codes: G01B 21/02 for measuring length, width, or thickness G01B21/10 takes precedence

Abstract

Method of determining the footprint of a tire on the ground, using devices already installed in standard production tires. Since the frequency of the transmitter clock present in a wheel unit is perturbed by mechanical vibrations when the tire contacts the ground, the frequency variations of the reference clock are representative of the value of the footprint. The method therefore includes determining the footprint on the ground of a tire of a wheel by measuring continuously, as a function of time, a signal representative of the variations in frequency of the reference clock supplied at the output of the time control device; determining a time interval during which the frequency variations of the reference clock occur; and, on the basis of the rotation speed of the tire, deducing therefrom an angular range of contact (Θ) corresponding to the footprint between the ends representing the ground contact length of the tire.

Claims

1. A method for determining the footprint of a tire (3) of a vehicle equipped with a monitoring system comprising one wheel unit (4) for each tire (3), each wheel unit (4) comprising a microcontroller (14), a speed sensor (12′

), a transmitter (10), a reference clock (16) of the transmitter (10) having a given frequency (F), and at least one time control device for the system (13, 32), which comprises;

continuously measuring, as a function of time (t), un signal (Δ

F/F₀, S, S′

) representative of the variations (Δ

F) of the frequency (F) of the reference clock (16) supplied at the output of the time control device (13, 32),

determining a time interval (T<sub>Δ

L</sub>) during which said variations of frequency (Δ

F) of the reference clock (16) occur, and

on the basis of the rotation speed of the tire (3), deducing therefrom an angular contact range (Θ

) corresponding to the footprint (Δ

L), representing the length of the contact of this tire (3) with the ground.

2. The footprint determination method as claimed in claim 1, comprising the following successive steps:

recording (30, 60, 60′

), as a function of time, the frequency (F) of the reference clock (16) and the variations (Δ

F) of this frequency (F) on the basis of said representative signal (Δ

F/F₀, S, S′

);

determining the time interval (T<sub>Δ

L</sub>) during which said representative signal (Δ

F/F₀, S, S′

) varies;

recording the rotation speed of the wheel (1) as a function of time;

deducing therefrom the angular contact range (Θ

) of the tire (3), corresponding to the time interval (T<sub>Δ

L</sub>) of the variations of frequency (Δ

F) of the reference clock (16);

defining a detection threshold (F_Min) below which said frequency variations (Δ

F) are disregarded;

if the frequency variations (Δ

F) are above the frequency threshold (F_Min), calculating the footprint (Δ

L) on the basis of the contact angle (Θ

), the time interval (T<sub>Δ

L</sub>) and the speed of the wheel (1);

defining boundaries (Δ

L_min, Δ

L_max) of the value of the footprint (Δ

L) beyond which the calculated value of the footprint (Δ

L) is not accepted;

defining a frequency of calculation for determining the value of the footprint (Δ

L) of the tire (3), and

restarting the calculation at the frequency thus defined.

3. The footprint determination method as claimed in claim 1, wherein the control device is a clock (13) of the microcontroller (14), and the signal representative of the variations (Δ

F) of frequency (F) of the reference clock (16) is the relative variation (Δ

F/F₀) of this frequency (F) timed by the frequency of the clock (13) of the microcontroller (14).

4. The footprint determination method as claimed in claim 3, wherein the clock (13) of the microcontroller (14) is calibrated by the reference clock (16) of the transmitter in an angular range located outside the contact angle (Θ

) corresponding to the footprint (Δ

L).

5. The footprint determination method as claimed in claim 1, wherein the control device is a phase lock detector (32) of a phase lock loop (20) with which the transmitter (10) is equipped, and the signal representative of the variations (Δ

F) of the frequency (F) of the reference clock (16) is a phase locking state information signal (S, S′

) supplied by the phase lock detector (32) to the microcontroller (14).

6. The footprint determination method as claimed in claim 5, wherein the locking state information signal (S) is supplied at the output of the phase lock detector (32) in the form of pseudo-digital values (60), and wherein a decision threshold (Δ

S) is defined such that the values of said information signal (S) at the output of said detector (32) are considered to have a value of “

one”

above this threshold (Δ

S) and a value of “

zero”

below this threshold (Δ

S), a period of time for which the signal (S) supplied by this detector (32) remains equal to “

one”

then corresponding to the time interval (T<sub>Δ

L</sub>) for which the wheel unit (4) is in the footprint (Δ

L).

7. The footprint determination method as claimed in claim 5, wherein the locking state information signal (S′

) is supplied directly at the output of the phase lock loop (20) in the form of digital values (60′

), varying between “

zero” and

“

one”

, a period of time for which the signal (S′

) supplied by said loop (20) remains equal to “

one”

then corresponding to the time interval (T<sub>Δ

L</sub>) for which the wheel unit (4) is in the footprint (Δ

L).

8. The footprint determination method as claimed in claim 2, wherein the control device is a clock (13) of the microcontroller (14), and the signal representative of the variations (Δ

F) of frequency (F) of the reference clock (16) is the relative variation (Δ

F/F₀) of this frequency (F) timed by the frequency of the clock (13) of the microcontroller (14).

9. The footprint determination method as claimed in claim 8, wherein the clock (13) of the microcontroller (14) is calibrated by the reference clock (16) of the transmitter in an angular range located outside the contact angle (Θ

) corresponding to the footprint (Δ

L).

10. The footprint determination method as claimed in claim 2, wherein the control device is a phase lock detector (32) of a phase lock loop (20) with which the transmitter (10) is equipped, and the signal representative of the variations (Δ

F) of the frequency (F) of the reference clock (16) is a phase locking state information signal (S, S′

) supplied by the phase lock detector (32) to the microcontroller (14).

11. The footprint determination method as claimed in claim 10, wherein the locking state information signal (S) is supplied at the output of the phase lock detector (32) in the form of pseudo-digital values (60), and wherein a decision threshold (Δ

S) is defined such that the values of said information signal (S) at the output of said detector (32) are considered to have a value of “

one”

above this threshold (Δ

S) and a value of “

zero”

below this threshold (Δ

S), a period of time for which the signal (S) supplied by this detector (32) remains equal to “

one”

then corresponding to the time interval (T<sub>Δ

L</sub>) for which the wheel unit (4) is in the footprint (Δ

L).

12. The footprint determination method as claimed in claim 10, wherein the locking state information signal (S′

) is supplied directly at the output of the phase lock loop (20) in the form of digital values (60′

), varying between “

zero” and

“

one”

, a period of time for which the signal (S′

) supplied by said loop (20) remains equal to “

one”

then corresponding to the time interval (T<sub>Δ

L</sub>) for which the wheel unit (4) is in the footprint (Δ

L).