FR2824904A1 - Determination of the absolute angular position of a motor vehicle tire by determining the phase of both a torsion sensor applied to the side of the tire and the phase of the wheel rim and then combining the two measurements - Google Patents

Abstract

Method for determining the angular position of a motor vehicle tire uses a torsion sensor attached to the side of the tire (10). The tire phase is measured using the torsion sensor attached to its side while the phase of the rim (12) is also measured. The absolute position of the tire is determined from a combination of the measurement. An Independent claim is made for a system for measuring the absolute position using both a torsion sensor mounted on the side of the tire and a sensor for measuring the phase of the wheel rim.

Description

duration of propagation of the light in the wavelength.

  The present invention relates to a method for determining the angular position of a sidewall torsion sensor of a tire, comprising the following steps: - the phase of the tire is measured by the sidewall torsion sensor, s and

  the phase of the rim associated with the tire is measured.

  The invention also relates to a system for determining the angular position of a sidewall torsion sensor of a tire comprising: o - means for measuring the phase of the tire with the sidewall torsion sensor, and - means to measure the phase of a rim associated with the tire. State of the art s Sidewall or sidewall torsion sensors are used in particular to exploit the torque transmitted by a wheel and a tire to the roadway or the instantaneous grip coefficient of the tires on the roadway. For this, it is known to integrate into the side wall (sidewall) of a tire, a large number of permanent magnetization zones distributed regularly at the periphery of the tire. It is in particular possible to integrate the permanent magnetization zones in the wall of the tire or to apply them to the wall. At a certain distance from the wall of the tire there is a measurement sensor which comprises at least two measurement elements

  2s installed at a different radial distance from the axis of rotation of the wheel.

  The variations in the magnetic fields linked to the rotational movement of the tire generate signals at the outputs of the measurement sensors. These signals represent the rotational movement of the tire. When under the effect of the forces applied to the tire or of the drive or braking torque to be transmitted, the tire deforms, this results in a phase shift of the measurement signals supplied by the measuring elements. This phase shift can be used as a measure of transmitted torques or instantaneous adhesion coefficients. ss In determining the phase of a tire, it was found to be elic at and linked to great s difficulties in achieving a homogeneous sinusoidal magnetization over the entire periphery of the tire. This is why correction methods are necessary to compensate for such imperfections in the magnetization. These corrections consist in measuring the magnetization of the tire as a function of the angular position and

  to record the relation of these quantities in a characteristic curve.

  By taking account of this characteristic curve, the drawbacks of this magnetization which is not perfect can be eliminated by calculation. However, to take account of this characteristic curve, it is necessary to know the absolute angular position of the magnetized pnenmatic because it is only in this way that the system will know which place of the character.

  which should be used to determine the correction data.

  Advantages of the invention The object of the invention is to develop a method of the type defined above making it possible to determine the absolute angular position of the tire from the measured phase of the tire and the measured phase of the rim. The measured phase of the tire is not sufficient alone to determine the absolute angular position. In that, however, in addition, the measured phase of the rim is taken into account, the absolute angular position of the tire can be determined. This can then

  to be used for correction procedures.

  The method is in particular advantageous in that one o sure me the phase of the rim with a polar wheel with N polar pairs or teeth, and the flank torsion sensor comprises M magnetic phases with M N. In this way the measurement signals from the side wall torsion sensor change with a different frequency than the measurement signals s from the pole wheel associated with the rim. Consequently, by comparing the two measurement signals, it can be concluded that the position

absolute angularity of the tire.

  In this context, it is particularly useful for the pole wheel used to measure the phase of the rim to be part of a sensor for the rotation speed of the ABS system. Anyway, the ABS speed sensors are available in many vehicles, so it is particularly economical to use their signals to detect

  undermine the absolute angular position of the tire.

  According to a particularly advantageous embodiment, if the torsion sensor comprises M magnetic phases with absolute value | M-N | = 1. The number of magnetic phases of the side or sidewall torsion sensor is thus precisely distinguished from one phase of the number of magnetization phases of the speed sensor of the ABS system. We can thus conclude with the absolute angular position of the tire by applying the vernier principle. The greater the number of polar pairs, the more precise the determination of the absolute angular position. If, for example, we have a polar wheel of the ABS speed sensor with 48 polar pairs and the sidewall torsion sensor has 47 magnetic phases, we can measure

  rerating the angular position with an accuracy of 360/48.

  The method according to the invention is advantageously characterized in that the tire connected integrally to the rim makes it possible to determine the phase Ph ante) of the rim by measuring a phase Ph (ImB) of an area d internal magnetization and of a phase Ph (AmB) of an external magnetization zone according to the formula: Ph (j ante) = k. (Ph (AmB) - Ph (ImB)),

  formula in which k is a constant of the tire.

  For the tire connected to the phase, the phase of the tire corresponds to that of the rim. If the phase of the tire is known only with respect to the rim and the phase of the rim itself, the rim being integrally associated with the speed sensor, using the

  vernier principle you can determine the absolute phase of the tire.

  o I1 is also advantageous for the method according to the invention that the ph as e me suré e of the pneumatics so it is co rrig e taking into account the absolute angular position of the tire. Thus knowing the absolute angular position of the tire makes it possible to improve the determination of the phase of the tire by using

  advantage of a side torsion sensor.

  It is also particularly advantageous for the measured phase of the tire to be corrected by applying a characteristic curve containing the magnetization of the tire as a function of its angular position. By knowing the absolute angular position of the tire it is possible to use a characteristic curve measured beforehand and which corresponds to the magnetization as a function

of the angular position.

  The invention also relates to a system of the above type, characterized by means for determining the absolute angular position s5 of the tire from the measured phase of the tire and

of the measured phase of the j ante.

  In this way we meet for the system, the advantages

ges of the process of the invention.

  It is particularly advantageous for a pole wheel to have N pairs of poles or teeth for measuring the phase of the rim, and the side wall torsion sensor comprises n magnetic phases with M N. By comparing the measurement signals oscillating with different frequencies it is possible to determine the absolute angular position of the tire. In the context of the system according to the invention, it is useful for the pole wheel used to measure the phase of the rim to be that of a sensor o of the speed of rotation of an ABS system. It is a particularly economical solution because many vehicles have such a system anyway.

speed sensor.

  According to a preferred embodiment of the system of the invention, the flank torsion sensor M has M phases magneti

  with absolute value | M-N | = 1.

  As the number of magnetic phases of the respective sensors is thus precisely distinguished from one phase, we can conclude that

  the absolute angular position by applying the vernier principle.

  In a system according to the invention, it is preferentially provided that for tires connected integrally to the rim, the phase Ph (rim) of the rim is determined by measuring a phase Ph (ImB) of an area of internal magnetization and of a phase Ph (AmB) of an external magnetization zone by the formula Ph ante) = k. (Ph (AmB) - Ph (ImB),

  s formula in which k is a constant of the tire.

  If the phase of the tire is known with respect to the rim and that of the rim itself, which is integrally associated with the rotational speed sensor, using the vernier principle, it is possible to determine

  complete the absolute phase of the tire.

  so that the measured phase of the tire is corri

  taking into account the absolute angular position of the tire.

  Overall, the phase of the tire can thus be determined with great precision using a sidewall or sidewall torsion sensor. s5 I1 is particularly advantageous for the measured phase of the tire to be corrected by taking account of a characteristic representing the magnetization of the tire as a function of its angular position. A characteristic measured beforehand gives the specific relationship to the tire of the magnetization and of the angular position of the tire. This knowledge and the knowledge of the absolute angular position thus make it possible to improve the accuracy of the determination.

of the tire phase.

  The present invention is based on the consideration that by the combination of a side wall torsion sensor and an ABS speed sensor, the absolute position of the side wall or sidewall torsion sensor can be determined. In particular it is then possible, if the number of magnetic phases of the side torsion sensor is

  o precisely distinguishes from one phase of the ABS speed sensor.

  Under these conditions, it is indeed possible to precisely determine the po

  absolute position by applying the principle of the vemier.

  Drawings The present invention will be described below in detail with the aid of preferred embodiments represented in the attached drawings in which: - Figure 1 is a schematic view of part of a wheel used to describe determining the phase of a tire, - Figure 2 shows several diagrams to describe the principle of the vernier,

  - Figure 3 is a block diagram for the description of the system

lon the invention.

  Description of the ex: example of realization

  FIG. 1 schematically shows part of a wheel s to explain the determination of the phase of a tire. A matt tire 1O is installed on a rim 12. This rim 12 has zones 14, 16, 18 of different permanent magnetization. These magnetizations alternate in polarity. For example, zone 14 of the North pole of a magnet is followed by zone 16 of the South pole, then zone 18 again of a North pole, etc. The tire 1O in FIG. 1 is shown in a state of torsion c that is to say that the area of the tire essentially the peripheral area of the tire 10 is offset. The zones of the tire 10 located radially on the outside are greatly offset than the zones located more on the inside; these are the zones which are closest to the rim 12. When at the different radial positions, that is to say for example at the level of the lines (a) and (b), measurement sensors are installed , it will be noted that for a deformation of the tire 1O due to the forces applied to the tire 1O or the drive torque or

  braking to be transmitted, there will be a phase difference between the metering signals

  sour emitted by the measuring elements installed according to lines (a) and (b).

  For a tire firmly connected to the rim, we will have the phase of the rim Ph ante) (line c) given by the following formula: s Ph ante) = k. (Ph (AmB) - Ph (ImB)), in this formula: Ph (AmB): represents the phase of the external magnetic zone for the line 10 (a) in figure 1, Ph (ImB): represents the phase of the inner magnetized zone for the line (b) of figure 1, Ph ante): phase of the rim for the line (c) in figure 1

K: tire constant.

  If the phase of the tire 10 is known with respect to the rim 12 and the phase of the rim 12 itself which is integrally connected to the speed sensor of the ABS system, it is possible to determine the

tire absolute phase 10.

  FIG. 2 shows how, on the basis of the quantities indicated above, the absolute phase of the tire can be determined. Figure 2 shows several diagrams used to explain the vernier principle used for this purpose. In the diagrams of figure 2 we have represented

  felt different sizes depending on the angle of rotation p of the wheel.

  FIG. 2a shows a sine or cosine function associated with the reception s of the measurement values for N pairs of poles. In the present case we have N = 2. Figure 2b shows corresponding sine / cosine curves linked to N + 1 = 3 pairs of poles. By forming the inverse function of the tangent function (Arctan) we obtain the functions represented in Figure 2d; Figure 2c corresponds to the sine / cosine curves from Figure 2a while Figure 2d corresponds to the sine or cosine curves of Figure 2b. Figure 2e shows how, by subtracting the functions shown in Figures 2c and 2d, the absolute phase is obtained. If the figures 2a and 2c are for example associated with the polar wheel of the rotational speed sensor of the ABS system and that FIGS. 2b and 2d correspond to the torsion sensor of the sidewall, then FIG. 2e shows that precisely after a wheel rotation of = 360 there will be a difference between the functions of Figures 2c and 2d equal to 0 modulo 360. This corresponds to a certain angular position of the sidewall torsion sensor (side wall). If there is a variation of the angular position ab solue, we will have the difference of 0 modulo 360 for another position of the wheel angle from which the absolute angular position of the sensor

flank twist.

  s Figure 3 shows a block diagram for description

  of a system according to the invention. The meaning of the symbols used in Figure 3 will first be given: 101: Phase measurement with a side torsion sensor, 102: Phase measurement with a polar wheel from the ABS system, o 103: Determination of the absolute phase according to the vernier method, 104: Correction of the phase measured by the side wall torsion sensor,: Result of the determination of the absolute phase in the functional element 103,

  s 106: Emission of the improved side torsion sensor phase.

  In the functional element 101, the phase of a side torsion sensor is measured. This phase, measured by the side torsion sensor, must be corrected in the functional element 104, for example using a characteristic curve containing information relating to the magnetic field as a function of the angular position. To reliably carry out such a correction in the functional element 104, it is necessary to know the absolute phase. For this, in the functional element 102, the phase of a polar wheel of the ABS system is measured. The phase measured in the functional element 101 and s that in the functional element 102 is combined according to the vernier principle. This method provides the result 105, namely the absolute phase. In the functional element 104, a characteristic curve is corrected from the measured phase and the absolute phase so that the functional element 106 can emit the

improved phase.

  The above description of the embodiment according to the

  The present invention serves for illustrative purposes without any limitation on the invention. Different variations and modifications are possible.

  in the context of the invention without departing from the framework of equivalents.

Claims (9)

CATI O N S REVENUE   1) Method for determining the angular position of a sidewall torsion sensor of a tire (10) comprising the following steps: - the phase of the tire (10) is measured by the sidewall torsion sensor, and - one measures the phase of the rim (12) associated with the tire (10), characterized in that, from the measured phase of the tire (10) and the measured phase of the rim (12), the angular position is determined absolute of pneumati o that (10).   2) Method according to claim 1, characterized in that - the phase of the rim (12) is measured with a polar wheel with N polar pairs or teeth, and - the flank torsion sensor comprises M magnetic phases with M N. 3) Method according to claim 1, characterized in that the pole wheel for measuring the phase of the rim (12) is part of a cap   speed of rotation of an ABS system.   4) Method according to claim 1, 2s characterized in that the flank torsion sensor comprises M magnetic phases with | M N | = 1. ) Method according to claim 1 characterized in that the pnenmatic (10) connected integrally to the rim (12) makes it possible to determine the phase Ph ante) of the rim (12) by measuring a phase Ph (ImB) d '' an internal magnetization zone and a phase Ph (AmB) of an external magnetization zone according to the formula: 3s Ph ante) = k. (Ph (AmB) - Ph (ImB)),   formula in which k is a constant of the tire.   6) Method according to claim 1, characterized in that the measured phase of the tire (10) is corrected taking into account the   absolute angular position of the tire (10).   7) Method according to claim 1, characterized in that the measured phase of the tire (10) is corrected by knowing a characteristic curve taking into account the magnetization of the tire   (10) as a function of the angular position of the tire (10).   8) System for determining the angular position of a sidewall torsion sensor of a tire (10) comprising: - means for measuring the phase of the tire (10) with the sidewall torsion sensor, and - means for measuring the phase of a rim (12) associated with the mat tire (10), characterized by means for determining the absolute angular position of the tire (10) from the measured phase of the tire (10) and the phase o measured from the rim (12).   9) System according to claim 8, characterized in that - a pole wheel has N pairs of poles or teeth to measure the: 5 rim phase (12), and - the side wall torsion sensor has n magnetic phases with M N.) System according to claim 8, characterized in that the pole wheel for measuring the phase of the rim (12) is part of a cap   speed of rotation of an ABS system.   1 1) System according to claim 8, characterized in that the flank torsion sensor M has M magnetic phases with va their absolute | M-N | = 1.   12) System according to claim 8, characterized in that for tires (10) connected integrally to the rim (12), the phase Ph ante) of the j ante (12) is determined by measuring a phase Ph s (ImB) of an internal magnetization zone and of a ph as Ph (AmB) of an external magnetization zone by the formula Ph ój ante) = k. (Ph (AmB) Ph (ImB),   formula in which k is a constant of the tire.   lO 13) System according to claim 12, characterized in that the measured phase of the tire (10) is corrected taking into account the   absolute angular position of the tire (10).   14) System according to claim 8, characterized in that the measured phase of the tire (10) is corrected taking into account the characteristic contained in the magnetization of the tire (10) in   function of the angular position of the tire (10).