Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
  • G01L5/00—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
  • G01M17/00—Testing of vehicles
  • G01M17/007—Wheeled or endless-tracked vehicles
  • G01M17/02—Tyres
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
  • B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
  • B60T8/17—Using electrical or electronic regulation means to control braking
  • B60T8/172—Determining control parameters used in the regulation, e.g. by calculations involving measured or detected parameters
  • B60T8/1725—Using tyre sensors, e.g. Sidewall Torsion sensors [SWT]

Definitions

• the present invention relates to vehicles and the measurement of the forces exerted by the roadway on vehicle tires.
• the present invention also relates to the various electronic assistance devices used for example for the anti-lock regulation of the brakes of a vehicle or the anti-skid regulation of the drive wheels, the trajectory control of a vehicle or even for other forms. control or monitoring such as tire pressure.
• ABS slip limitation systems
• the invention starts from the observation that all the forces exerted by the road surface on the vehicle are transmitted via the wheels. It is the balance of these forces which conditions the accelerations undergone by the vehicle. So the determination of all of these forces could make it possible to dispense with the various sensors mentioned above or to supplement them to provide more complete information.
• the method of the invention is based on the observation that the forces acting between the tread of the tire and the road cause a substantial and reproducible deformation in the form of a circumferential extension or contraction of the sidewalls of the tires.
• This circumferential extension or contraction deformation if it is possible to measure it in isolation during the rotation of the tire in real time, can make it possible to know at all times the direction and intensity of the forces acting on the tire as well as the sign and the intensity of the self-alignment torque exerted by the tire.
• the inflation pressure is one of the parameters of the method proposed here.
• This pressure can be known by a specific measurement means independent of the measurements made in the context of this invention, an example of such a means being a pressure sensor.
• This pressure can also result from a specific treatment for the measurement of circumferential deformations.
• Camber is one of the parameters of the method proposed here.
• the camber can be known by a specific measurement means independent of the measurements made in the context of this invention, an example of such a means being a camber angle sensor. This camber can also result from a specific treatment for the measurement of circumferential deformations.
• the invention proposes a method for determining at least one of the characteristics chosen from the three components of a result of forces exerted by the roadway on the contact area of a tire and the self-alignment torque generated. by tire and camber and pressure, characterized in that said characteristic is determined by processing at least two circumferential extension or contraction measurements in at least one sidewall of the tire at two fixed points in space, located at different azimuths along the circumference.
• the invention proposes to estimate the contraction or the circumferential extension of the flanks by measuring the distance between the wires of the carcass ply in the flanks.
• the circumferential extension includes a component due to the bending of the flank, in particular during of the passage in the contact area (Phenomenon also called "rabbit belly").
• This component due to bending is in no case a problem and can be used to increase the dynamics of variation of the signals used by the invention by carrying out the extension measurement elsewhere than on the neutral fiber in bending.
• Figure 1 is a perspective of a tire on which we define conventions useful to the intelligence of the invention; • Figures 2a and 2b show the effect of the vertical component Fz:
• FIGS. 3a and 3b show the effect of the component Fx: - where the solid curve corresponds to a vertical load of 400 daN and an absence of force Fx, - where the dotted curve corresponds to a vertical load of 400 daN and an Fx force of 400 daN (Motor),
• FIG. 5 shows the deformation of the tire when a camber angle is applied
• FIG. 7 shows the neural network architecture
• Figure 8 shows examples of transfer functions
• FIGS. 9a and 9b show two examples of architecture allowing the inflation pressure of the tire to be taken into account if it varies
• Figure 10 shows the raw and filtered time signal
• Figure 11 shows the identification of the passage in the contact area from the time signal
• FIG. 12 shows an example of operation with a sensor and a model
• FIG. 13 shows an example of operation with three sensors and a model
• Figure 14 shows an example of operation with three sensors and two models.
• each force applied to the tire in the contact area causes a modification of the circumferential extension of the sidewalls of the tire.
• the vertical component presses the tire on the ground. By creating a contact area, it causes a variation in the distance between the two points Ai and A 2 when the assembled assembly is in rotation, reflecting a modification of the circumferential extension of the sides.
• Figures 2a and 2b show the distance between points A and points B, respectively, depending on the azimuth at which they are located.
• the increase in the vertical component applied leads to an extension of the two flanks in the contact area (increase in the distance around 180 °) and a contraction of the other areas of the flank, mainly at the entry and exit of the contact area. (decrease in distance everywhere else, mainly around 135 ° and 225 °).
• FIGs 3a and 3b illustrate the effects of the component Fx of the applied forces, indicating the distance which separates points A and points B respectively, depending on the azimuth at which they are find.
• a positive Fx force is applied (motor torque)
• the two sides are compressed in the circumferential direction at the entry to the contact area and in extension at the exit from the contact area (Decrease in distance to 135 ° and increase to 225 °).
• a negative Fx force is applied (braking torque)
• the two sides are compressed in the circumferential direction at the exit of the contact area and in extension at the entry (Decrease in the distance to 225 ° and increase to 135 °).
• the self-alignment torque N (moment around the vertical axis) is not strictly speaking another force acting between the tread of the tire and the road. It is rather a consequence of the way in which the components Fx, Fy and Fz are applied in the contact area. If the point of application of the resultant having as components Fx, Fy and Fz is not the center of the contact area, this resultant generates a moment around Oz which we call self-aligning couple. The presence of this moment mainly results in a rotation of the contact area around Oz. This effect results for example in a circumferential extension at the entry of the contact area and a circumferential contraction at the exit from the contact area on one side while on the other side there is a circumferential contraction at the entry of the contact area. and a circumferential extension at the outlet of the contact area with respect to a situation with zero self-alignment torque.
• FIGS. 6a and 6b show the evolution of the circumferential deformation in the two flanks. On the overloaded sidewall (Points A), the evolution is similar to that of an increase in the load. On the other flank (Points B), there is an evolution compatible with a decrease of. the load carried.
• the apparent rigidity of a tire comes from both its pneumatic functioning (its inflation pressure) and its structural rigidity (rigidity of its architecture).
• the measured circumferential deformation signals also contain a pneumatic component and a structural component.
• the deformation signals of a tire inflated to 2 bars and loaded to 400 daN along Z are not identical to those delivered by the same tire to 2.5 bars and loaded to 500 daN. This difference corresponds to the structural contribution and can make it possible to estimate the inflation pressure of the tire.
• the links which connect the applied forces and the deformation signals are quantitatively modified, but without their nature being changed.
• the extension rates in the sidewalls are influenced by the pressure and by the load; they are composed of a contribution due to the "pneumatic" operation (ie dependent on the inflation pressure) and another contribution due to the structural operation (ie of the constituent materials of the tire and their arrangement) , which does not change when you change the pressure, where you can go back to the pressure.
• the method can be explained first in the case of an inflation pressure assumed to be constant for the sake of simplicity.
• the camber is constant and zero to make the explanation clearer and only mention the most interesting cases with regard to this parameter.
• One of the advantages of the proposed method is to allow a separation of the contributions of each component of the applied stress, so as to allow an estimation of each of these components.
• the approach used is based in part on remarkable parity characteristics which correspond to the natural symmetries of the tire to achieve this separation.
• azimuth ⁇ the angle at which we analyze the circumferential extension of the flanks.
• the origin of the azimuth is taken away from the center of the contact area.
• the center of the contact area therefore has the azimuth 180 °.
• the extension signal as a function of the azimuth s ( ⁇ ) can then be broken down into two signals s p ( ⁇ ) and s t ( ⁇ ) such as:
• s is called odd part and s p even part of s.
• s ⁇ ( ⁇ ) and s 2 ( ⁇ ) be the signals associated with the measurement of the circumferential extension on each sidewall of the tire.
• s p is called the even part on the side and s 1 the odd part on the side.
• the forces Fx, Fy, Fz and the self-alignment torque N are due to their orientations linked to certain symmetries.
• this principle can be used to decouple the effects of the stress components on the tire.
• the symmetries which apply make it possible moreover to affirm that the signal s, 1 is mainly related to the self-alignment torque N.
• the method explained here proposes to carry out measurements of the circumferential extension on at least one sidewall of the tire. These measurements make it possible, thanks to mathematical operations (linear or non-linear combinations between the measurements carried out at the different azimuths) to estimate the values of the signals s, p s p 's p p and s, 1 in certain azimuths and thereby to provide an assessment of the components of the applied force.
• mathematical operations linear or non-linear combinations between the measurements carried out at the different azimuths
• we present here some examples of use of the method which are not exhaustive and in no way limit the configurations that can be used to those listed here.
• V 2 -V 1 is used to estimate the imbalance between the contact area input and the output. This value will be mainly linked to the component Fx.
• An estimate of Fx is given by f x (r 2 V 2 -r ⁇ V ⁇ ) where ri and r 2 are positive real coefficients and f x a continuous monotonic function.
• V c - (V ⁇ + V 2 ) makes it possible to estimate the difference between the passage in the contact area and the outside of the contact area. The result here is mainly related to Fz.
• An estimate of Fz is given by f z (s c V c - (s ⁇ V ⁇ + s 2 V 2 )) where if, s 2 and s c are positive real coefficients and f z a continuous monotonic function.
• V c + V ⁇ + V 2 gives an indication of the overall extension of the flank. This value will mainly be linked to the component Fy of the applied force.
• An estimate of Fy is given by f y (u c V e + u ⁇ V ⁇ + U 2 V 2 ) where ui, u 2 and u c are positive real coefficients and f y is a continuous monotonic function.
• V ⁇ 1 -V ⁇ 2 + (V 2 1 -V 2 2 ) gives the even component in azimuth and odd in flank. This combination is therefore directly linked to Fy.
• An estimate of Fy is given by f y (e ⁇ V ⁇ '+ e 2 V 2 1 -f ⁇ V ⁇ 2 -f 2 V 2 2 ) where ei, e 2 , fi and f 2 are positive reals and f y is a continuous monotonic function.
• V ⁇ '-V ⁇ 2 - (V2 1 -V 2 2 ) gives the odd component in azimuth and odd in the side. This combination is therefore directly linked to N.
• N An estimate of N is given by fn (g ⁇ V ⁇ 1 -g 2 V 2 1 -h ⁇ V ⁇ 2 + h 2 V2 2 ) where gi, g 2 , hi and h 2 are positive reals and f n a continuous monotonic function.
• V c 'and V c 2 be the values measured at these azimuths.
• V c 'and V c 2 allow a certain redundancy of the information but above all a better estimate of the component Fz.
• Example 2 the fact of having five circumferential deformation measurements in five different azimuths on each flank makes it possible to distinguish the contributions of the component Fy and of the camber angle. This configuration therefore makes it possible to simultaneously assess the camber angle and the force components under running conditions with variable camber.
• the measurements on the two flanks provide a certain robustness. Indeed, because of the “load transfer” from one side to the other when the camber angle is not zero, a model using a measurement on the two sides and providing the sum of the estimates given by each side is by construction valid regardless of the camber angle.
• the linear combinations taken as an example above are very rudimentary and only allow the main effects to be taken into account.
• the method described uses more advanced transfer functions to link the measurements to the estimates of the forces. Any interpolation function allowing a link to be established between the measured quantities and the values of the components of the applied stress can be used in this context. We can thus determine the coefficients of the interpolation function from a learning base (see below).
• the neural networks seem well adapted to establish a transfer function between the measurements carried out and the components of the forces Fx, Fy, Fz and N.
• the camber angle can also be part of the quantities to be estimated and appear at the output of the transfer function.
• one can retain as an interpolation function allowing to establish a link between the measured quantities and the values of the components of the applied stress the use of networks to a layer of hidden neurons and a layer of output neurons. These hidden neurons use a sigmoid transfer function.
• the output neurons use a linear transfer function ( Figure 7).
• Figure 7 The parsimony property of this type of network used as an approximator is very interesting here. It is possible to use a network by component to be estimated or a network allowing, thanks to several outputs, to estimate all the components.
• the first step consists after having determined the azimuths of measurement to collect the values of the circumferential extension of the sidewall (s) during various stresses on the tire chosen so as to cover the whole area in which the evaluation of the chosen characteristic (s) will be allowed in normal use.
• the stresses chosen must also implement all the couplings likely to be encountered during normal use.
• the set of measured values and the associated chosen characteristic (s) constitutes the learning base.
• the second step consists in learning the network weights (more generally, determining the coefficients of an interpolation function) on the basis thus constituted. At the end of this phase, the transfer functions are available.
• a third step consists in testing the transfer functions by comparing the estimates of the chosen characteristic (s) with the values indicated by another means of measurement.
• a first way of proceeding consists in correcting the forces estimated at the output of the transfer function as a function of the pressure. It is thus possible to carry out a first order correction. Indeed, either a stress applied to the tire in the case of a transfer function which does not take the pressure into account. If the pressure is twice the reference pressure (at which the transfer function has been established), the transfer function will see approximately half the deformation measured at the input than for the reference pressure. It will therefore evaluate efforts that are half as weak than the efforts actually applied. The estimated efforts should be doubled.
• the first consists in using a pressure measurement given by a pressure sensor different from the specific sensors of the invention.
• the measured pressure value is then supplied to the system, in addition to the azimuth deformation values to the transfer function (s).
• Figure 9a shows schematically the associated architecture.
• the second approach consists in estimating the inflation pressure from measurements of the circumferential flanks.
• the deformation signals have a structural component and a pneumatic component which allows, by their analysis, to capture information on the inflation pressure.
• FIG. 9b schematizes the architecture which results from this approach.
• the method then provides, without an additional sensor, an estimate of the inflation pressure.
• the number of measurement points can be greater than the minimum configurations presented in the examples and allow a more precise or more reliable result due to the redundancy of the information available.
• An alternative to increase the precision or the robustness of the method consists in using a multidimensional measurement in place of a mono-dimensional measurement or in supplementing the measurement of extension in the circumferential direction by another measurement.
• a circumferential deformation in an area of the sidewall close to the tread and another measure of circumferential deformation in an area of the sidewall close to the bead.
• the inputs of the transfer function are made up of a mixture of measurements of one or the other or of the different types of deformations at different azimuths. Apart from this difference, we then use exactly the same approach for determining the transfer function.
• the measurement of the circumferential extension of the sidewall (s) of the tire can be done in any way, by an external device or a device internal to the tire.
• an external device or a device internal to the tire.
• the use of one or more sensors placed in the tire and therefore driven in rotation by the tire is described.
• This or these sensors integrated into the tire and locally measuring the circumferential extension of the sidewall (s) can use any physical measurement principle. It may for example be dielectric sensors measuring a variation in capacitance linked to the distance which separates two electrodes.
• the electrodes may consist of a conductive wire placed radially in the sidewall. This arrangement allows a measurement of the "wire gap" by measuring the capacitance between the electrodes.
• the sensor can be powered either by the vehicle by remote power supply by a battery on the wheel or in the tire or by any other means.
• the sensor itself can provide information continuously or with a sufficiently rapid refresh rate relative to the period of rotation of the wheel.
• This approach using a sensor integrated into the tire has the advantage of allowing knowledge of the circumferential extension of the sidewall (s) to all azimuths of the tire since a sensor, driven by the tire, explores all the azimuths during a wheel rotation.
• the method of reconstruction of the components of the forces being based on the measurement of the circumferential extension at certain azimuths, the problem arises of the localization of the sensor to extract the values at the right azimuths.
• the sensor is interrogated at a constant and known frequency. It therefore delivers a time signal of the variation of the local circumferential extension.
• a measured signal is presented in FIG. 10.
• On this temporal signal it is easy to recognize the signature of a revolution of the wheel that we observed previously (FIGS. 1a, 1b, 2a, 2b 3a and 3b).
• this signal is noisy.
• the first operation consists in reducing this noise by applying a low-pass filter, the cut-off frequency of which can be linked to the speed of rotation of the wheel.
• This measurement of the angular position of the wheel can, for example, be obtained by counting the transitions of an ABS sensor of the speed of rotation of the wheel.
• the invention proposes to use the signal from the sensor or any other sensors integrated into the tire to estimate the angular position of the wheel.
• Each passage of the sensor in the contact area has as signature a very strong circumferential extension of the sidewalls of the tire.
• the simplest method to carry out this operation consists in carrying out a thresholding of the filtered signal and in seeking the maxima among the values higher than this threshold ("algorithm 1" - figure 11).
• This approach makes it possible not to detect the maxima which do not correspond to the passage through the contact area.
• the shape of the signal changes significantly as a function of the forces applied. In real conditions, thresholding can be complicated, because the threshold level must be constantly adapted. In addition, under certain conditions, it happens that the fact of applying a threshold causes the detection of several extrema per revolution of the wheel. This situation is encountered when a significant Fy force is applied.
• algorithm 1 Use by default the previously explained algorithm called "algorithm 1".
• a periodicity use the date of the last passage in the contact area and an evaluation of the speed according to the last passages to predict the date of the future passage in the contact area t n .
• the estimation of the speed of rotation can be used at the input of the transfer function to improve the precision of the estimation of the components of forces over a large range of speeds.
• Several possibilities are then available for implementing the measure. Indeed, the determination of the components of the forces requires measurements at several azimuths.
• a first approach consists in using only one sensor on each side for which one wishes to have measurements. At each passage to a required position, the value given by the sensor is taken into account to refresh the measurement at the azimuth considered.
• a single sensor thus makes it possible to obtain the measurements at all the azimuths necessary for the reconstruction of the forces.
• Figure 12 shows this type of operation with a model (transfer function) which requires measurements at three azimuths (0 °, 120 ° and 240 °).
• a second approach consists in placing several sensors on the circumference so that at least once per revolution the sensors are simultaneously at the azimuths at which one wishes to make a measurement. It is thus possible to obtain an image of the deformation of the tire in different azimuths at a given instant, which no longer requires that the forces vary slowly with respect to the rotation of the wheel. Ideally (maximum bandwidth), the number of sensors should be at least equal to the number of quantities to be estimated.
• One implementation of this approach consists in placing the sensors evenly distributed around the tire. Thus, in the case where N sensors have been placed, the situation where the sensors are correctly positioned occurs at least N times per revolution. Figure 13 shows this type of operation with three sensors which fall three times per revolution on the azimuths where the measurement must be made (0 °, 120 ° and 240 °).
• the first uses measurements at 0 °, 120 ° and 240 °, the second at 60 °, 180 ° and 300 °.
• the transfer function can be applied.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Transportation (AREA)
• Mechanical Engineering (AREA)
• Tires In General (AREA)
• Force Measurement Appropriate To Specific Purposes (AREA)
• Measuring Fluid Pressure (AREA)
• Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)
• Arrangements For Transmission Of Measured Signals (AREA)

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• 2002
  • 2002-08-02 WO PCT/EP2002/008619 patent/WO2003014693A1/fr active Application Filing
  • 2002-08-02 EP EP02767302A patent/EP1417470A1/de not_active Withdrawn
  • 2002-08-02 JP JP2003519377A patent/JP4479993B2/ja not_active Expired - Fee Related
  • 2002-08-02 CN CNB028155203A patent/CN1245615C/zh not_active Expired - Fee Related
  • 2002-08-02 KR KR10-2004-7001891A patent/KR20040023725A/ko not_active Application Discontinuation
• 2004
  • 2004-02-05 US US10/773,015 patent/US7203603B2/en not_active Expired - Fee Related

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