Method for obtaining the distance traveled by a rotating tire

Abstract

1. A method for obtaining a distance traveled by a tire, the method comprising: A sensor capable of generating a signal proportional to the acceleration applied is placed at a radial position R. C and rotating the tire at a rotational speed W under a load Z; and after a time interval T, generating a first signal Sig containing the amplitude of acceleration in a direction perpendicular to the crown. i where a value less than the threshold N corresponds to less than 40% of the length of the first signal; i The reference quantity V is the square root of the average value of i reference and a step of identifying the distance D traveled during the time T, as shown in [Formula 1] D = A * T * V i reference , where A is proportional to the square root of the rolling radius of the tire; Includes.

Description

Technical Field

[0001] The present invention relates to a method for obtaining the distance traveled by a tire casing under its use conditions of an assembled body that has been mounted.

Background Art

[0002] Knowing the total distance traveled by a tire casing is important for evaluating the condition of the tire casing, for example, from both its wear and aging perspectives. This is an easily obtainable quantity that reflects the condition of the tire casing. Therefore, by knowing this quantity, it becomes possible to plan maintenance work on the tire casing in order to maintain the mobility of the vehicle equipped with the tire casing, or even to perform inspections or replacements of the tire casing. Of course, it is more valuable to know this quantity because it is most suitable for evaluating the condition of the tire casing for the tire manufacturer that designed and manufactured the tire casing. Finally, this total travel distance is the sum of the distances traveled regularly during the service life of the tire casing. Also, obtaining this regularly traveled distance provides a good indicator regarding the condition of the tire casing, particularly for predicting the life of the tire casing.

[0003] In the prior art, there are two main systems of devices for evaluating the travel distance, which are the result of the configuration of the assembled body that has been mounted. As an example, U.S. Patent No. 9,566,834 (B2) discloses a TPMS device attached to a wheel of an assembled body that has been mounted, whereby the travel distance traveled by the assembled body can be determined through a correct evaluation of the centrifugal force measured by an accelerometer. In this case, it is necessary to attach an accelerometer to the wheel of the assembled body, which is a non-deformable solid. Furthermore, it is necessary to correct the signal from the accelerometer with respect to the temperature of the assembled body, which is measured by the TPMS device.

[0004] The drawback of this device is that it is necessary to further measure the acceleration and provide a TPMS (acronym for Tire Pressure Monitoring System) attached to the wheel, for example, to the valve rim. Under harsh operating conditions, due to the heat generated from the brake disk, temperature correction due to heat exchange between the brake disk and the wheel is required. Finally, this device only requires the use of an accelerometer for this purpose, which is expensive even if the assembly implemented using the accelerometer can detect whether it is rotating or stationary in order to save the device output at rest.

[0005] Among the second type of devices, US Patent No. 9,050,865 (B2) can be cited, which proposes placing an accelerometer included in a TMS (acronym for Tire Monitoring System) on the tread of the tire casing for the purpose of evaluating the distance traveled by the tire casing. In that case, the operation consists of evaluating the number of wheel rotations over a given time interval so as to be able to evaluate the distance traveled and the average rotational speed. This measurement needs to be repeated after a given time interval. The rotational speed of the tire casing is estimated, for example, by interpolation between two measurement phases, between two measurement phases. To detect the number of wheel rotations, it is recommended to use at least one impact-sensitive accelerometer to record the large acceleration changes that occur when the tread of the tire casing enters or exits the contact patch corresponding to the area where the tire casing touches the ground. Therefore, the absolute value of the radial acceleration is never necessary. However, due to the angular accuracy regarding the detection of the contact patch length, an estimated value of the load supported by the implemented assembly can be obtained.

[0006] The drawbacks of such a device lie in the angular accuracy required for detecting entry to or departure from the ground plane. Furthermore, the power consumption of the system is also high. It is necessary to evaluate various time intervals, the time intervals of the measurement phases, and the time intervals between the measurement phases, and calculate the rotational speed of the implemented assembly, which is calculated based on the rotational speed of each measurement phase and the duration during which no measurement is performed. This result is accurate and no acceleration measurement sensor is required to measure the true acceleration, but this system is not very suitable for powering long-life measuring devices. Furthermore, the power source, generally a battery, is located radially outside with respect to the axis of rotation of the tire casing, so it is generally small to reduce centrifugal force and thus has a low capacity, that is, this device is not very suitable for actual use, especially in long-life tire casings.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Means for Solving the Problems

[0008] The present invention relates to a method for obtaining the distance traveled by a tire casing provided with an electronic device vertically attached to the crown of the tire casing, the method being energy-efficient and executed in real time, and the traveled distance can be directly obtained by the electronic device.

[0009] The present invention is a method for obtaining the distance traveled by a tire casing mounted on a wheel to form an assembled body, the tire casing comprising a crown provided with a tread capable of contacting the ground, two sidewalls and beads, and having a meridian plane, the intersection of the meridian plane and the natural rotation axis defining the wheel center, the method comprising: - fixing at least one sensor perpendicular to the crown with respect to the tire casing, the sensor having a radial position R with respect to the natural rotation axis when mounted on the wheel, and capable of generating at least one output signal proportional to the acceleration received by the sensor within the tire casing; C - rotating the assembled body at a rotational speed W and placing it under conditions where a load Z is applied; - after a time interval T, obtaining a first signal Sig comprising at least the amplitude of the acceleration in the direction perpendicular to the crown, the value of the first signal Sig being less than a threshold N corresponding to less than 40% of the length of the first signal Sig; i i i - identifying a first reference quantity V defined as the square root of the average value of the first signal Sig; i i reference - determining the distance D traveled during the time interval T using [Equation 1] where A depends on the tire casing and is at least proportional to the square root of the radius of rotation corresponding to the minimum distance between the wheel center and the ground in the inflated state under load; - optionally, determining the total distance D traveled from time t0 to time t + T using f [Equation 2] A step of determining using JPEG0007706452000002.jpg11157, where D0 is the total distance traveled by the tire casing from time t0 to time t, and the step; includes.

[0010] This method first enables the sensor to be arranged perpendicular to the crown block, whereby the sensor can be used for other purposes, such as estimating the load supported by the mounted assembly. In addition, since the sensor is separated from the heating elements of the vehicle, such as the brake disc, the measurement of the vertical acceleration that is not affected by the temperature of the mounted assembly is ensured. Therefore, it is not necessary to correct the value of the vertical acceleration for temperature. In addition, since the mathematical operations performed are limited to calculations of comparison, summation, average value, and multiplication by time intervals, the energy efficiency is good. Therefore, it is perfectly conceivable to execute the operation within the electronic device integrated in the tire casing, but it is also possible to transfer some of these operations to the vehicle or the server using communication means, such as radio frequency communication means. In this case, the periodicity of the radio frequency communication is preferably higher than the periodicity between two measurement phases, especially when the communication consumes a lot of power. Finally, by ensuring that the value of the first signal Sig i is positioned at least proportionally above the threshold value N, it is ensured that the estimation of the travel distance D within the time interval is realistic or of good quality. In addition, it is also ensured that the estimated value of the travel distance during the time interval is significant. Specifically, the threshold value N allows for tolerating signal disturbances related to the measurement system or the ground. In addition, if most of the values of the first signal are negative or close to zero, it is an indication of signal mismatch, or small centripetal acceleration, or measurement at the azimuth angle of the tire casing corresponding to the ground contact surface. In all these cases, since the travel distance does not represent the reality, it is recommended not to evaluate it. The threshold value N enables the detection of these specific values of the first signal Sig i .

[0011] Positioning the sensor adjacent to the crown on the tire casing, contrary to the prior art U.S. Patent No. 9,566,834 (B2) that positions the sensor on the wheel, in particular due to the impact recorded by the sensor when it enters or exits the ground contact surface, or due to the roughness of the ground through which the mounted assembly passes above it, a lot of noise is added to the acceleration measurement signal. For example, the sensor passing through the ground contact surface leads to the measurement of a vertical acceleration value close to zero that does not represent the centrifugal acceleration at all.

[0012] Such an influence is greatly reduced when the sensor is incorporated into the wheel, which is an object that does not deform with respect to the tire casing under driving conditions. Therefore, regardless of the angular position of the sensor at the time of signal recording, by improving the signal / noise ratio, a good approximation of the centrifugal acceleration can be obtained. This shows the justification for performing a single measurement of the vertical acceleration in the prior art.

[0013] To solve this problem, it is necessary to calculate the average of the vertical acceleration of the sensor so as to obtain a realistic value of the centrifugal acceleration unless the values less than the threshold N in the first signal account for the majority. For example, this threshold N is a zero value.

[0014] Finally, to estimate the travel distances D and Df, it is necessary to know two variables. The first is the time interval T that has elapsed between two consecutive measurements. The second is the function A, which is proportional to the square root of the radius of rotation Rp. Here, the radius of rotation Rp is the minimum distance between the wheel center and the outer peripheral point of the tire casing to which a load is applied in the running state. As a result of the load Z being applied, the tire casing is pressed against the ground, so this distance is generally the orthographic projection of the wheel center onto the ground. Generally, from the time corresponding to the first use of the tire casing on the vehicle, regarding the total distance Df that the tire casing has traveled, it is sufficient to obtain the distance D0 by adding the distances traveled during each time interval T' preceding the time interval T, and then adding the distance D traveled during the time interval T. Of course, these time intervals T' are not necessarily the same as or equal to the time interval T. Similarly, the function A of the tire casing may change from one time interval to the next as a result of external or internal factors of the implemented assembly.

[0015] Preferably, the time interval T remains the same between each measurement, and when the first signal Sig i cannot be obtained at time t, the reference quantity V i reference is preferably taken as the set value V set and the total distance D f that the tire casing has traveled is [Equation 3] determined using the formula of JPEG0007706452000003.jpg26157.

[0016] In this way, the time interval T can be factored out of the sum. Therefore, this reduces the number of calculation times to be executed, is more economical in terms of power and time, and makes this method efficient in terms of the calculation time in the electronic device integrated in the tire.

[0017] In addition, as a result of specific mechanical, thermal or electromagnetic stresses on the implemented assembly, if the recording of the acceleration measurement signal is very noisy, instead of individual measured values, set values relative to a reference quantity can be used so as not to distort the total travel distance. This set value can be, for example, the previous value V of the reference quantity i-1 reference , or a part thereof, or even take on a zero value.

[0018] Preferably, the function A is constant and the total travel distance is [Equation 4] determined using JPEG0007706452000004.jpg26157.

[0019] Therefore, the function A can be factored out of the sum. Therefore, this reduces the number of calculations to be performed, is more economical in terms of power and time, and makes this method efficient in an electronic device integrated in a tyre. For this purpose, an approximation is necessary such that the rolling radius R P does not change over the service life of the tyre casing. In that case, the rolling radius R P is calculated only once by applying the calculation rules of ETRTO (acronym for European Tyre and Rim Technical Organisation) based on the information included in the markings of the tyre casing. For example, the load Z applied to the tyre casing is the load specified by the load index marked on the sidewall of the tyre casing and the ETRTO calculation rules. In addition, if there is an inflation pressure P, it is the recommended inflation pressure optionally indicated on the sidewall according to the ETRTO calculation rules.

[0020] According to a particular embodiment, the first signal Sig i is segmented over the number N TdR of wheel rotations, where N TdR is greater than or equal to 1 and N TdR is preferably an integer, and to construct the wheel rotation signal Sig TdR i a reference quantity Vi reference is the square root of the average value of the wheel rotation signal Sig over one rotation. TdR i Here, since the first signal Sig corresponds to at least one complete rotation of the implemented assembly, it is guaranteed that the low-level value corresponds to less than 40% of the length of the first signal Sig. Furthermore, the average value of the acceleration perpendicular to the crown over one rotation of the wheel is a quantity specific to the rotation of the implemented assembly, which can significantly improve the quality of the estimation of the travel distance, especially over a short distance, for example, in terms of daily evaluation. When the first signal Sig is segmented over a plurality of wheel rotations, the repetition of the wheel rotation can smooth the required specific quantity by reducing the weight of the spatial discretization regarding the recording of the first signal Sig. Therefore, in order to improve the quality of the prediction, the first signal Sig preferably corresponds to a plurality of wheel rotations. In addition, even if the signal does not correspond to an integer number of wheel rotations, the remainder does not significantly affect the required specific quantity. In this way, a very high-quality approximation of the distance traveled by the implemented assembly is obtained. Of course, if there is no remainder, apart from the discretization error, this means segmenting the first signal Sig over an integer number of wheel rotations, resulting in the required specific quantity being obtained with higher accuracy and leading to the best estimation of the travel distance.

[0021] According to a specific embodiment, after identifying the first continuous increment I corresponding to the abscissa value u of at least the first signal Sig exceeding the threshold B, the first signal Sig i is defined by i the integer number N defined in [Equation 5] i i i i i i TdR JPEG0007706452000005.jpg16157.

[0022] [Equation 5] JPEG0007706452000005.jpg16157 TdR ​​​Over the wheel rotation, it is partitioned between a first increment Imin and a second increment Imax, where max is equal to min + 2k and k is an integer of strictly positive natural numbers.

[0023] This is a simple way regarding the partitioning of the first signal Sig over an integer number of wheel rotations, minimizing complex operations on values. It is efficient in terms of computation time and memory space, thereby enabling implementation in an electronic device integrated into the tire casing while avoiding high power consumption, and thus the power supply size of the electronic device can be limited. Here, it is not required to determine whether the threshold B is exceeded from above or below, only the crossing is recorded. Therefore, to partition the first signal Sig over an integer number of wheel rotations, it is necessary to use only even or odd increments. When evaluating the direction of exceeding the threshold B, only the abscissa value u corresponding to either an even or odd increment I will be directly specified. This is within expectations but results in a high computational cost. i According to a specific embodiment, the first continuous increment I is i - a step of defining a threshold B which is a value composed between 0.1 and 0.5 of at least one maximum value of at least one part of the first signal Sig

[0024] - a step of determining a second signal of the abscissa value u depending on at least one part of the first signal Sig - the first signal Sig i and the threshold B; - a step of identifying a first continuous increment I corresponding to the abscissa value u of at least one part of the first signal Sig when the second signal exceeds a threshold E, where the second signal is preferably the difference between the first signal Sig i and the threshold B and the threshold E is the value zero, or the second signal is the ratio between the first signal Sig and the threshold B and the threshold E is the value 1, the step i and is identified using a combination of i - the first signal Sig i and the threshold B, and the threshold E is the value 1, the step and is identified using a combination of

[0025] This method can be easily implemented in an electronic device integrated into the tire casing because the mathematical operations to be performed are simple. To determine the threshold, it is necessary to hold the maximum value of a part of the first signal Sig i Specifically, a specific form of the vertical acceleration perpendicular to the crown of a rotating tire casing under such a load ensures that a threshold B is generated that can remove the part of the first signal Sig i corresponding to the passage of the ground contact surface of the tire casing. However, it is sufficient to simply demarcate this area relative to others and position the increment I. Then, by selecting the second function as the difference or ratio between the first signal and the threshold, the data processing time in the electronic device can be limited, and a simple threshold crossing function can be used.

[0026] According to one advantageous embodiment, the determination of the increment comprises - creating a second continuous increment J corresponding to an intermediate abscissa value u, which is defined by the abscissa value u of a continuous identical Even-odd property increment I, preferably located between 1 / 8 and 7 / 8 of the length, and very preferably at the midpoint of the length; - constructing a wheel rotation signal Sig min between the first increment J max and the second increment J TdR i where min and max are the same Even-odd property ; and including.

[0027] In this embodiment, the first signal can be demarcated over an integer number of wheel rotations. However, this time, the signal is not explicitly demarcated by entry into or departure from the ground contact surface, but by an intermediate position, very preferably a position on the opposite side of the ground contact surface. In fact, it is necessary to move away from the regions corresponding to both entry into and departure from the ground contact surface, which cause large variations in the vertical acceleration at any point on the crown of the tire casing. Therefore, the intermediate point is the same Even-odd propertyIt is generally preferably located between one-eighth and seven-eighths defined by the increment I. As a result, the first signal Sig i The average value of the increment is less susceptible to the influence of errors caused by the spatial discretization of wheel rotation. Specifically, since the sensitivity of the vertical acceleration at the entry to or departure from the ground surface is high, a small positioning error results in a large variation in the vertical acceleration, and in order to improve the estimation accuracy of the travel distance, it is necessary to take the average of more measurement points. When the section of the signal is outside the influence area of the ground surface, the recorded value is generally close to the desired specific value, so the error due to spatial discretization is small. Therefore, it is easy to limit the length of the first signal Sig i to one rotation of the wheel, and thereby the number of measurement points is also limited.

[0028] Advantageously, the rotational speed W of the tire casing is [Equation 6] greater than the threshold value W defined by JPEG0007706452000006.jpg26157, in which case the first signal Sig threshold is acquired, where Dev is the distance traveled by the tire casing in one rotation. i

[0029] Therefore, when the rotational speed exceeds the threshold value, although it is easy to separate the first signal Sig i with respect to the threshold value N, it is unpredictable. The first signal Sig i varies, for example, as a result of a road surface with a large macro roughness, electromagnetic interference affecting the measurement system, and / or vibrations of the tire casing. When this threshold value W threshold is not reached, a set value V i reference which can also be set to a zero value as the reference quantity V set can be adopted.

[0030] Reference acceleration γ referencecorresponds to the neutral state of the tire casing, i.e., the state where the load is zero. In practice, this itself appears in the built-in assembly that constitutes the mounted assembly that rolls on the ground without undergoing the deformation to form the ground contact surface. Ultimately, this corresponds to the acceleration that the sensor would experience when the sensor is attached to the tire casing in a state where the tire casing rotates freely around its natural axis of rotation.

[0031] As a result, the reference acceleration γ reference is simply the centripetal acceleration that the sensor would experience when attached to a freely rotating tire casing. Therefore, in order to specify the reference acceleration, the following two parameters are required. That is, the radial position R of the sensor with respect to the natural axis of rotation C and the rotational speed W of the tire casing to which the sensor is fixed.

[0032] According to the second embodiment, the reference acceleration γ reference is determined based on the average value of the wheel rotation signal Sig TdR .

[0033] Specifically, this method assumes that, in a state of freely rotating at the rotational speed W, the tire casing or some sensor attached thereto experiences a centripetal acceleration proportional to its radial position with respect to the natural axis of rotation. When the tire casing is pressed against a hard ground and receives a load, the tire casing deforms so as to distribute the deformation energy generated by this load between two situations. The first situation corresponds to the conditions regarding the movement required by the ground contact surface and tends to reduce the centripetal force energy. The second situation is the condition regarding the energy delivered to the tire casing outside the ground contact surface. This delivered energy complements the reduction in the centripetal force energy corresponding to the first situation. As a result, regardless of whether the tire casing is receiving a load Z or not, the average value of the wheel rotation signal over an integer number of wheel rotations corresponds to the centripetal acceleration that the sensor experiences.

[0034] Preferably, the wheel rotation signal Sig is generated for a given angular position of the tire casing. TdR After fixing the phase of the wheel rotation signal Sig, in order to take into account the effect of the Earth's gravity, TdR A correction Corr is applied to the

[0035] Compensation for the Earth's gravity allows to minimize errors during deformation of the tire casing, especially at low rotation speeds. In particular, when the tire casing rotates, the sensor rotates around its natural axis of rotation. The signal it outputs is then proportional to the radial acceleration and is therefore tainted by the Earth's gravity. Over one revolution of the wheel, the Earth's gravity generates a sinusoidal signal with an amplitude g that depends on the height of the sensor in the Earth reference frame. This parasitic signal Corr is therefore calculated as a first signal Sig i This is the first signal Sig i This requires that the rotational speed of the tire be synchronized with the angular position of the tire casing.

[0036] Of course, the higher the rotational speed W of the tire casing, the more the centrifugal acceleration experienced by the sensor will dominate this parasitic signal.

[0037] Very advantageously, the reference quantity V reference The time interval T between two assessments is less than or equal to 10 minutes, preferably less than or equal to 5 minutes, very preferably less than 2 minutes.

[0038] The simplicity of this method is based in part on this time interval T. That is, the larger it is, the fewer calculations need to be performed on the integrated electronic device, thereby saving energy. However, there is no need to sacrifice the quality of the estimation to save energy. The general idea is to obtain the mileage in one day, one week, one month, or the service life of the tire casing, so there is no need to obtain accurate measurements at predetermined intervals. Specifically, if the result is statistically correct on the desired time scale, the goal is achieved. For this purpose, by measuring once every 10 minutes, an accurate estimate on a daily basis can be obtained. However, to make the usage profile of the tire casing irrelevant, this time interval T needs to be reduced to 5 minutes. Finally, to be accurate for evaluations on a time scale of several hours, the time interval needs to be reduced to 2 minutes. However, to improve the quality of the total mileage estimation on a time scale of at least one hour for the use of the tire casing, there is no need to make the time interval less than 30 seconds. In the case of standard use of the tire casing, using a time interval of less than 30 seconds cannot achieve any further significant improvement in accuracy.

[0039] Now, the tire casing defines a radius of rotation R P and the function A is [Equation 7] proportional to the ratio B of JPEG0007706452000007.jpg20150.

[0040] Specifically, the function A can be defined by the ratio B of the radius of rotation R P to the sensor position radius R C . These two radii are determined with respect to the natural axis of rotation of the assembled body. However, while the radius R P is evaluated in the loaded state of the tire casing, the sensor position radius R C is determined in the unloaded state of the assembled body. Of course, the proportional relationship between the function A and the ratio B can be unity or another parameter.

[0041] Specifically, the rolling radius R P depends on the load Z supported by the tire casing.

[0042] When the tire casing is mounted on a rim of a given diameter and width, and in some cases is below the maximum nominal load indicated by its load index, and in some cases is inflated to the recommended pressure, the value of the radius of the tire casing pressed against the flat part of the ground can be set to the nominal R P value. However, in practice, the rolling radius R P varies with the load Z it supports. However, as a first approximation, since the variation in the rolling radius with respect to the actual value of the rolling radius R P can be ignored, it is sufficient to either adopt a representative quantity or consider the variation due to the load dependence applied at each instant of measurement.

[0043] Specifically, the tire casing is inflated to the inflation pressure P, and the rolling radius R P and the radial position R C depend on the inflation pressure P of the tire casing.

[0044] Similarly, in the case of an inflated tire casing, the rolling radius R P and the position radius R C may be affected by the inflation pressure of the tire casing. In this case, if necessary, it may be necessary to consider the variation of these two radii due to the inflation pressure in order to improve the accuracy obtained over the distance traveled by the tire casing. As a first approximation, the inflation pressure determined by applying the ETRTO rules can be used to obtain a very satisfactory first estimate of the total distance traveled.

[0045] Specifically, the rolling radius R P depends on the total distance D f traveled by the tire casing.

[0046] The rolling radius R P changes as a result of the natural wear of the tread. The wear of the tread depends on the total distance D fis linearly proportional to. Therefore, by taking this dependency into account, the evaluation accuracy of the travel distance is improved. For example, it is necessary to consider the variation according to the dependency set for the total travel distance over a long period that is much longer than the time interval T between two measurements. However, as a first approximation, since the variation in the radius of rotation with respect to the actual value of the radius of rotation R P can be ignored, the representative quantity of the radius of rotation R P may be adopted as described above.

[0047] According to one specific embodiment, the first signal Sig i is acquired at a constant sampling frequency.

[0048] When samples are acquired regularly, since the variation in the rotational speed W of the assembled body implemented is small over a small number of wheel rotations, a spatial discretization of the first signal Sig i that is substantially constant spatially is obtained. Therefore, considering that the reference quantity V reference is the average value of the wheel rotation segments where the samples are spatially distributed, this method is robust. In addition, this constant sampling is easy to implement in an electronic device integrated into the tire casing

[0049] According to an advantageous embodiment, the spatial discretization of the sampling of the first signal Sig i is less than 10 degrees, preferably less than 6 degrees, and very preferably less than 3 degrees.

[0050] Although not essential, in order to be able to identify the ground contact surface, that is, the region of the tire casing in contact with the ground, under normal rotation conditions of the assembled body implemented, it is preferable that the spatial discretization of the acceleration of the rotating wheel is minimized. In particular, when the length of the signal Sig i is large, this information can be used to indirectly identify the increment for differentiating the passage of the ground contact surface. Of course, the finer the spatial discretization of the first signal Sig i , the higher the detection accuracy and the shorter the required length of the first signal. In that case, over a single wheel rotation or over a small number of wheel rotations, the reference quantity Vreference can obtain very good evaluation. Thus, the length of the first signal Sig i is always almost the same in two measurement methods, either spanning a small number of wheel rotations with high-level discretization or spanning a large number of wheel rotations with low-level or medium-level spatial discretization. Both solutions provide a correct evaluation of the traveling distance as long as at least one wheel rotation is completed.

[0051] For example, when it is desired to evaluate the distance traveled by the tire casing with a wheel-tire assembly, the sensor needs to be associated with an electronic unit comprising a microcontroller, a memory space, a battery, and a clock. In that case, since spatial discretization at a constant sampling frequency is assumed, simple operations can be performed by the microcontroller, and battery consumption can be minimized. In addition, by having a minimum discretization of about 36 points per wheel rotation, it is possible to limit the number of operations and transfers to the memory space. Nevertheless, the accuracy obtained regarding the deformation of the tire casing is well maintained, while the battery of the electronic unit is conserved. That is, only the intermediate scalar value of the method needs to be saved or transferred. The present invention will be better understood by reading the following description of application examples to pneumatic tires. This application example is given merely illustratively, and the following attached drawings are referred to.

Brief Description of the Drawings

[0052]

Figure 1

Figure 2

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Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

[0053] In order to implement the present invention, the tire casing must be equipped with an electronic unit comprising a sensor, a microcontroller, a clock, a memory space and energy storage means, and wireless frequency communication means capable of transmitting and possibly receiving. The tire casing includes a crown that rotates around the natural axis of rotation, two sidewalls, and two beads. Further, the casing includes a meridian plane that is equidistant from the two beads, and the intersection between the meridian plane and the natural axis of rotation defines the wheel center.

[0054] The sensor is fixed in a radial position R with respect to the natural axis of rotation while attached to the wheel, towards a protruding material element or longitudinal groove that is a region of uniform rigidity. C and is fixed perpendicular to the crown with respect to the tire casing. The sensor can generate at least one output signal proportional to the acceleration perpendicular to the crown received by the sensor within the tire casing. In fact, this sensor can be a uniaxial sensor, in which case the uniaxial sensor needs to be positioned radially. It can also be composed of a plurality of uniaxial sensors. In that case, in order to reconstruct the acceleration perpendicular to the crown of the tire casing, the orientation of each uniaxial sensor needs to be clearly identified with respect to the coordinate system of the tire casing. The sensor takes into account the continuous component of the acceleration. The sensor can be an acceleration sensor using piezoresistive technology or capacitance technology.

[0055] The electronic unit is powered by energy storage means and controlled using a clock by a microcontroller. The microcontroller has, for example, a calculation algorithm installed that enables it to determine a reference quantity V of the tire casing using signals generated by sensor elements. reference A transmission means for radio frequency communication is used to transmit the calculated information, and a reception means for radio frequency communication is used to receive operating instructions or usage information for the calculation algorithm. Ideally, this electronic unit includes or is associated with other measuring elements (for example, means for evaluating inflation pressure, temperature of the internal cavity of the mounted assembly, tread wear condition, etc.) so that component sharing can optimize the operating cost.

[0056] In this case, the sensor is activated by the microcontroller when the tire casing is in a running state. Of course, a threshold value for the rotational speed W can be selected, and a signal output by the sensor is obtained from that threshold value. The electronic unit can utilize a memory space suitable for the type of analysis it desires to perform. In fact, the capacity of this memory space is predefined in advance according to the use of the electronic unit. It is the microcontroller that controls the storage of values from the sensor into the memory space. In addition, the microcontroller can perform simple mathematical and logical operations on a small amount of data. When the mathematical and logical operations are quite complex or the number of data to be operated on increases, the microcontroller is replaced by a microprocessor. Finally, the electronic unit is powered by energy storage means. The simplest storage means is a battery. However, a large capacitor that can be recharged using a piezo element is also envisioned.

[0057] Depending on the sampling frequency of the electronic unit, a wide range of rotational speeds W can be covered with a spatial discretization of less than 10 degrees. According to one particular embodiment, the sampling frequency is adaptable according to requirements or in response to a signal such as the rotational speed W of the tire casing.

[0058] Optionally, the electronic unit can include or acquire identification information of the tire casing. This information is useful for the selection of a useful data set for the calculation algorithm used in the electronic unit. If the electronic unit needs to acquire the identification information of the tire casing or needs to receive an instruction to perform a measurement, the electronic unit is equipped with radio frequency receiving means. The radio frequency receiving means operates in a low frequency range, ideally at a frequency of 125 kHz, so as to be free from interference generated by the metal area of the tire casing and its surrounding environment within the vehicle.

[0059] According to one particular embodiment, the electronic unit specifically has high frequency transmitting means known as the BLE (Bluetooth (R) Low Energy) band within the UHF (ultra high frequency) band, particularly near 433 MHz or 900 MHz or in an unused frequency band. In addition, the UHF band makes it possible to have a small antenna size and facilitates the incorporation of the electronic unit into the tire casing.

[0060] This transmission communication is useful for transmitting the data of the present method to the vehicle or outside the vehicle. It is possible to either transmit a data sequence corresponding to the acquisition of the first signal Sig i or the wheel rotation signal Sig TdR or to transmit an intermediate result to be calculated by the electronic unit. Since the data flow is not very large in the two transmission modes, the power consumption of the electronic components is necessarily small. Specifically, high frequency transmission consumes more power than mathematical operations and logical operations.

[0061] Figure 1 shows in gray the first raw signal 1b corresponding to the vertical acceleration perpendicular to the crown of a track tire casing rotating at a constant rotational speed W. Regularly and periodically, the curve 1b passes through low, near-zero values. This periodic phenomenon corresponds to the sensor passing through the ground contact surface of the tire casing. The transition between the sensor passing through the ground contact surface of the tire casing and passing through other parts of the tire casing occurs abruptly on the falling or rising side depending on whether the sensor is entering or leaving the ground contact surface. Additionally, it should be noted that the first signal 1b follows the carrier wave on a scale of one wheel rotation and oscillates around this carrier wave at a frequency higher than the rotational frequency of the wheel. These oscillations correspond to noise on the first signal 1b from the sensor, and this noise is due to various unpredictable effects including the macro-roughness of the road.

[0062] The curve indicated by the subscript 1 in black represents the signal of the same accelerometer corrected only with respect to the gravity of the earth, and this signal will be referred to as the corrected first signal 1. The correction here is a sine wave and is applied to the point located at the center of the ground contact surface, that is, the point equidistant from the two edges that define the boundary of the part of the signal that is near zero. It can be seen that the first signal 1 is flatter between the regions characterizing the ground contact surface. Although not essential, it is preferred that the various steps of the method be performed on this corrected first signal 1.

[0063] Figure 2 shows a method for evaluating the influence that the spatial discretization and the length of the first signal Sig i exert on the reference acceleration value γ reference based on which the reference quantity V reference is based, and the distance D and D f traveled by the tire casing. Accordingly, the thick gray continuous curve shows the first signal (referred to as 1) corresponding to the vertical acceleration corrected by gravity at one-degree angular steps over multiple wheel rotations, and its depiction is intentionally limited to approximately one rotation. The average value of this signal is, by definition, the reference acceleration γ referencetends towards and is represented by the continuous straight line 4. The same average value will be obtained for integer wheel rotations, regardless of whether this signal is gravity-corrected or not. This value is used as a reference and is equal to 100 by default.

[0064] A second first signal Sig represented by the black triangle (referred to as 10) i corresponds to the same signal 1, but in this case, the spatial discretization of the signal is 10 degrees. To form the wheel rotation signal Sig TdR it is possible to limit the length of this signal to one rotation of the wheel by combining samples located at near-zero values. Since this signal 10 necessarily has near-zero values for each sample per ground contact, this level of spatial discretization teaches that at least the acceleration measurement signal can be separated into one rotation of the wheel, and that this event can be detected under standard operating conditions of a conventional tire casing. Of course, beyond this maximum angular discretization, it may not be possible to identify the ground contact of the sensor using the acceleration measurement signal. Considering only the Sig TdR for a complete rotation of the wheel, the average value of this signal, equal to 99% of the value of the reference acceleration γ reference is obtained, which is very satisfactory.

[0065] Finally, a third first signal Sig represented by the light grey circle and referred to as 11 icorresponds to the same signal 1, but in this case, the spatial discretization of the signal is 10 degrees and the sampling is limited to the first 5 increments, i.e., a portion of one wheel rotation. In FIG. 2, the dashed line (referenced by 3) represents the threshold N. Here, the threshold N corresponds to 50 percent of the maximum value for the acceleration measurement signal without gravity correction over one rotation. Note that few of the points of signals 10 and 11 fall below this threshold N. Further, the lengths of signals 10 and 11 are selected such that at least 60 percent of the signal length is located above this threshold N. In the case of signal 11, since the length of signal 11 is equal to 5 and two values are below this threshold N (representing 40 percent of the signal), exactly 60 percent of the length of signal 11 is located above this threshold. In this case, the average value of signal 11 is equal to 90% of the reference acceleration γ reference which is satisfactory as a valid estimate of the travel distance can be obtained using it. If this signal 11 were limited to the first 4 values, then in that case, the condition regarding the length of the signal exceeding the above N would not be met and the average value would drop to 79% of the reference acceleration. Further, if the last 4 values of signal 11 were used, then in that case, the condition regarding the threshold N would be met and the average value would be 110 percent of the reference acceleration, which would still be quite satisfactory. Note that changing the threshold N would not change the results much either. However, when using the raw acceleration measurement signal without gravity correction, this threshold N must be carefully selected as the signal may not pass through zero due to the value of gravity.

[0066] FIG. 3 shows a method for determining the wheel rotation signal Sig TdR (referenced by 2 in the figure) over integer wheel rotations. Here, a corrected first signal Sig i is used to determine the threshold E indicated by the dashed line 3 for better illustration of the example. Here, the threshold E is set to half of the maximum amplitude of the uncorrected first signal Sig i . Successive increments I are identified, which, for example, from below, the first signal Sig iis the location where it crosses the dashed line 3, which physically addresses the detachment of the sensor that rotates integrally with the tire casing from the ground surface. Therefore, here, in response to entry into the ground surface, the crossing from above the threshold value E by the first signal Sigi, which would generate the intermediate increment I, is ignored. Therefore, the first signal Sig i is the wheel rotation signal Sig between the first increment (here I1) and the second increment (here I3) TdR (referred to in 2). The wheel rotation signal Sig TdR here represents the acceleration measurement signal of the sensor over two complete rotations of the wheel.

[0067] The threshold value E represented by the dashed line 3 is, in this case, evaluated in a part of the first signal Sigi using a variable sampling frequency. The maximum discretized value obtained is extracted from this part of the first signal and named MAX. Therefore, the threshold value E is a value that lies between 10 and 50% of the value MAX, and in this example, this value is approximately 50%.

[0068] The reference acceleration γ represented by the black solid line 4 reference corresponding to the average value of the wheel rotation signal Sig TdR (referred to in 2) over one rotation is calculated. This is done by summing the values of the increments u of the first wheel rotation signal Sig TdR and dividing that sum by the number of increments of the wheel rotation signal Sig TdR at the end of the wheel rotation signal Sig TdR of the first wheel rotation signal Sig TdR This is evaluated in real time. For this, it is sufficient to find the first crossing from below by the first signal for the threshold value E, which determines the starting point of the wheel rotation signal Sig TdR (referred to in 2). Of course, this calculation can also be done after all the records of the wheel rotation signal Sig

[0069] Figure 4 shows the wheel rotation signal Sig from the acceleration measurement signal TdRIndicates the segmentation of (referenced by 7 and shown in gray). Here, the second embodiment is used for this segmentation.

[0070] To better explain this example, a threshold B shown by the dashed line 5 is determined from the signal delivered by the corrected sensor. Successive increments I are identified, which are the points where the first signal crosses the dashed line 5, and this physically corresponds to the sensor integrated with the tire casing entering or leaving the ground contact surface. Next, considering only the odd-numbered increments I in this explanatory diagram, successive increments J are constructed that are equidistant from the odd-numbered increments I. These increments are identified by the vertical dotted lines in FIG. 3. Of course, this method can be applied as long as the selected increments are between 1 / 8 and 7 / 8 of the signal length included between two increments I i and I i+1 .

[0071] Next, the wheel rotation signal Sig TdR (referenced by 7) is segmented between a first increment (here J1) and a second increment (here J3). The wheel rotation signal Sig TdR here represents the acceleration measurement signal delivered by the sensor over two complete rotations of the wheel.

[0072] The threshold B represented by the dashed line 5 is, in this example, evaluated at a variable sampling frequency on a portion of the acceleration measurement signal. The obtained discretized maximum value is extracted from this portion of the acceleration measurement signal and named MAX. Thus, the threshold B is a value between 10 and 50% of the value MAX, and in this example, this value is approximately 50%.

[0073] The reference acceleration γ represented by the solid black line 6 reference is determined by calculating the average value of the first wheel rotation signal Sig TdR (referenced by 7). This sums the values of the increments u of the wheel rotation signal between increments J1 and J3, and then divides this sum by the number of increments of the wheel rotation signal at the end of the first wheel rotation signal Sig TdRIt is evaluated in real time by dividing by the number of increments u (referenced by 7).

[0074] This second embodiment is a better method because the discretization error at the extreme values of the wheel rotation signal Sig TdR causes only slight variations in the calculation of the reference acceleration. Specifically, at these extreme values, the sensitivity of the signal is low with respect to the sensitivity of the signal level with respect to the increment I.

[0075] FIG. 5 shows an acceleration measurement signal corresponding to the acceleration perpendicular to the crown of a truck tire casing that is pre-corrected for the gravity of the earth and rotates at a variable rotational speed W.

[0076] Here, a threshold value E represented by the dashed line 3 is determined with respect to the wheel rotation signal Sig TdR (shown in light gray and referenced as 2).

[0077] The threshold value E makes it possible to identify, for example, the increment I corresponding to the sensor leaving the ground surface. In this analysis, the wheel rotation signal Sig TdR is preferred to limit the error related to the variation of the rotational speed W of the tire casing, so it is limited to one rotation of the wheel. The threshold value E is segmented over an integer number of wheel rotations and is selected to correspond to half of the reference acceleration of the first signal that is before the wheel rotation signal 2. Also, the reference acceleration γ reference is determined by calculating the average value of the wheel rotation signal 2 shown by a continuous curve (referenced by 4) from the wheel rotation signal 2.

[0078] Also, here it should be noted that since the rotational speed W is variable in the acceleration phase, the period related to the wheel rotation decreases, resulting in rising or falling edges that are increasingly closely spaced.

[0079] Figure 6 illustrates the speed profile of trucks used regionally in Europe. This vehicle is equipped with an assembled body with sensors according to the present invention, and the assembled body is attached to the front of the vehicle. The response of the sensors was recorded at a predetermined time interval T of about one minute. The sampling frequency of the sensors was selected so that the conditions of the signal length and the minimum angle step size were satisfied throughout the usage-related range of the speed during the measurement phase. The daily mileage was estimated by an integration device at a measurement frequency of one minute. For this purpose, function A was selected to be ratio B. Rotation radius R P and the position radius R of the sensor C were pre-calibrated on a test bed in the loaded and unloaded states by applying the ETRTO rules. Furthermore, the signals were stored in an external memory space, which made it possible to change the time interval T between the measurement phases and thus perform other evaluations. Furthermore, the distance traveled by the vehicle during the day was recorded directly by the vehicle's speedometer and also via a commercially available GPS device.

[0080] Figure 7 summarizes the differences between the mileage recorded by the vehicle and various evaluations of this method where only the time interval T between the measurement phases was changed in one-minute increments from one minute to forty minutes. The first evaluation at one minute was that of the device incorporated in the assembled body. The other evaluations were performed by deleting the raw data and increasing the time interval T between the measurements. Here, for a given evaluation regarding the daily mileage, the time interval T remained constant.

[0081] It should be noted that when the time interval T is less than 10 minutes, the difference in distance between the distance recorded by the vehicle and the distance evaluated by this method does not exceed 5 percent. For this particular schedule, if the time interval is set to 20 minutes, the error in the estimated value still does not exceed 10 percent. Furthermore, the shorter the time interval T, the smaller the difference between the reference value recorded by the vehicle and the evaluated value by this method. When the time interval T between the measurement phases is less than 5 minutes, the error is even smaller.

Explanation of symbols

[0082] 1 The first signal corresponding to the gravity-corrected vertical acceleration 3 Dashed line (threshold value) 4 Continuous straight line (average value of the signal) 10 The second first signal 11 The third first signal

Claims

1. A method for obtaining the distance traveled by a tire casing mounted on a wheel to form an implemented assembly, wherein the tire casing has a crown with a tread capable of contacting the ground, two sidewalls, and beads, and a meridian plane, and rotates around a natural rotation axis, and the intersection of the meridian plane and the natural rotation axis defines the wheel center, - A step of fixing at least one sensor perpendicular to the crown with respect to the tire casing, the sensor having a radial position R with respect to the natural rotation axis in a state of being attached to the wheel C and capable of generating at least one output signal proportional to the acceleration received by the sensor within the tire casing. - placing the implemented assembly under conditions where it can rotate at a rotational speed W and a load Z is applied; - After a time interval T, obtaining a first signal Sig including at least an amplitude of an acceleration in a direction perpendicular to the crown i wherein a value of the first signal Sig i that is less than a threshold value N corresponds to less than 40% of a length of the first signal Sig i - the first signal Sig i a first reference quantity V defined as the square root of the average value of i reference identifying; and - the distance D traveled during the time interval T, 【Equation 1】 is determined using, where A depends on the tire casing and is at least proportional to the square root of the radius of rotation Rp corresponding to the minimum distance between the wheel center and the ground under a loaded state, A method comprising.

2. The time interval T remains the same between each measurement, and when the first signal Sig i cannot be obtained at time t, the reference quantity V i reference takes the set value V set , and the total distance D traveled by the tire casing f is 【Equation 3】 The method for obtaining the distance traveled by the tire casing according to Claim 1, determined using.

3. The function A is a constant, and the total distance D f is 【Equation 4】 The method for obtaining the distance traveled by the tire casing according to Claim 2, determined using.

4. The first signal Sig i is segmented over the number of wheel rotations N TdR where N TdR is 1 or more, and in order to construct the wheel rotation signal Sig TdR i the reference quantity V i reference is the square root of the average value of the wheel rotation signal Sig TdR i over one rotation, a method for obtaining the distance traveled by the tire casing according to any one of claims 1 to 3.

5. At least a first signal Sig exceeding a threshold value B i After identifying a first continuous increment I corresponding to the abscissa value u of i the first signal Sig is 【Equation 5】 The integer number of times N defined by TdR Over the wheel rotation of min Between the first increment I max And the second increment I, where max is equal to min + 2k, max and min represent natural numbers, and k is an integer of strictly positive natural integers. The method for obtaining the distance traveled by the tire casing according to claim 4.

6. The first continuous increment I is - the first signal Sig i defining a threshold value B which is a value composed between 0.1 and 0.5 of at least one maximum value of at least one part of - the first signal Sig i determining a second signal of at least one of the parts and the abscissa value u depending on the threshold value B; - the first signal Sig before the second signal exceeds the threshold value E i identifying the first continuous increment I corresponding to the abscissa value u of at least one part of the, wherein the second signal is the difference between the first signal Sig i and the threshold value B, the threshold value E is zero, or the second signal is the first signal Sig i and the ratio between the threshold value B, and the threshold value E is unity, step; The method for obtaining the distance traveled by the tire casing according to Claim 5, identified using a combination of.

7. The identification of the increment is - creating a second continuous increment J corresponding to an intermediate abscissa value u between the abscissa values u of the increments I of the same parity in succession; First increment J min and the second increment J max between which the wheel rotation signal Sig TdR i is constructed, a step in which min and max have the same parity, A method for obtaining the distance traveled by the tire casing according to Claim 5 or 6, comprising.

8. The rotational speed W of the tire casing is 【Equation 6】 Threshold value W defined by threshold When it is larger than i the first signal Sig is acquired, where Dev is the distance traveled by the tire casing in one revolution, the method for acquiring the distance traveled by the tire casing according to any one of claims 1 to 7.

9. the reference amount V reference The method for obtaining the distance traveled by the tire casing according to any one of claims 1 to 8, wherein the time interval T between the two evaluations regarding reference is 10 minutes or less.

10. The tire casing defines a rolling radius R P and the function A is 【Equation 7】 The method for obtaining the distance traveled by the tire casing according to any one of Claims 1 to 9, proportional to the ratio B of.

11. the rotational radius R P A method for obtaining the distance traveled by a tire casing according to any one of claims 1 to 10, wherein the rotational radius R depends on the load Z supported by the tire casing.

12. The tire casing is inflated to the inflation pressure P, and the turning radius R P and the radial position R C is a method for obtaining the distance traveled by the tire casing according to any one of claims 1 to 11, which depends on the inflation pressure P of the tire casing.

13. The radius of rotation R P is a method for obtaining the distance traveled by the tire casing according to claim 2 or claim 3, which depends on the total distance Df traveled by the tire casing.

14. The first signal Sig i is a method for obtaining the distance traveled by the tire casing according to any one of claims 1 to 13, which is obtained at a constant sampling frequency.

15. The sampling spatial discretization of the first signal Sig i is less than 10 degrees, a method for obtaining the distance traveled by a tire casing according to any one of claims 1 to 14.

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