System and method for measuring tire footprint length

Abstract

The present invention relates to a system for measuring the footprint length of a tire (10). In particular, the system includes a first electronic device (1) and a second electronic device (2), each configured to acquire, filter, store, and transmit data, and a processing device (3) external to the electronic devices (1, 2), configured to receive and process the data transmitted by at least each electronic device (1, 2) to measure the footprint length based on an angle (β) between a first axis (B1) passing through a center (O) of the tire (10) and a first contact point (CP1) between a portion of the tire (10) and the ground, and a second axis (B2) passing through a second contact point (CP2) between the center of the tire (10) and the ground. The present invention also relates to a method for measuring the footprint length of a tire (10).

Description

[Technical field]

[0001] The present invention relates to a system for measuring the length of a tire footprint.

[0002] In particular, the present invention relates to a vehicle (especially an agricultural vehicle) Tire footprint The invention relates to a system structure configured to measure length based on a chord relative to an angle between an axis passing through the center of the tire and a first point of contact between a portion of the tire and the ground, and a second axis passing through the center of the tire and a second point of contact between that portion of the tire and the ground beyond which that portion of the tire leaves the ground, when the tire is in use.

[0003] The system comprises at least a first electronic device that, in use, is mounted on an inner or outer surface of the tire, and a processing device that is external to the at least first electronic device.

[0004] Preferably, the system further comprises a second electronic device mounted on the rim, each electronic device configured at least to acquire, filter, store and transmit data to said processing device, said processing device configured at least to acquire and process the acquired data in order to measure the footprint of the tire.

[0005] "Footprint" means the contact area between the tire and the ground.

[0006] The contact surface is an area that is smaller than the overall dimension of the tire.

[0007] The present invention also relates to a method for measuring the length of a tire's footprint on a ground surface. [Background technology]

[0008] As is known, the shape of a tire's footprint is defined by a length (ie, the vertical dimension of the footprint) and a width (ie, the horizontal dimension of the footprint).

[0009] When the same load is applied to a tire, the tire footprint length changes depending on the tire pressure. i. High tire pressure reduces the tire's footprint length on the ground (in other words, limits the tire's deflection on the ground), ii. With low tire pressure, the tire's footprint length on the ground is greater (in other words, the tire's deflection on the ground is greater) than the footprint length under the conditions described above.

[0010] 1A and 1B show an agricultural vehicle tire and its footprint, respectively, when the tire pressure is high.

[0011] 1C and 1D show an agricultural vehicle tire and its footprint, respectively, when the tire pressure is low.

[0012] The footprint of an agricultural vehicle determines such things as traction, soil compaction, and fuel consumption per unit surface area worked by the agricultural vehicle.

[0013] Currently, systems are known that are capable of measuring the length of the contact area between the tire and the ground and are described in the international application WO2019101849A1.

[0014] The system comprises a monitoring unit associated with the tire, the monitoring unit comprising at least a sensor for measuring values ​​representative of the deformation of the tire in use.

[0015] In particular, said quantity is measured at a certain time and sampling frequency during a rotation of the tire, and each time said quantity is measured the system is capable of determining whether the measured quantity has a value representative of a passage of a monitoring unit corresponding to said contact area, such that a first number of times within a time interval a monitoring unit has passed corresponding to said contact area is obtained.

[0016] Based on the above values ​​of the number of times, the sampling frequency, and the time interval, parameters are estimated, and tire monitoring is performed based on the estimated parameters.

[0017] The measurement of the length of the contact area is based on statistical methods, in particular on the probability "p" that the monitoring unit will be located corresponding to the contact area during the rotation of the tire.

[0018] The larger the value of the parameter, the longer the time that the monitoring unit is located corresponding to the contact area within the time interval, and therefore the higher the probability of finding the monitoring unit in a state corresponding to the contact area during the rotation of the tire.

[0019] For example, this probability "p" may be equal to the ratio of the number of measurements representing the passage of a monitoring unit corresponding to the contact area to the number of measurements, according to the following formula: PL=2πRp where R is the radius of the tire.

[0020] However, systems of the known type described above have a drawback due to the fact that the presence of a sensor within the footprint zone is not certain but is described by probability, and therefore the length of the footprint cannot be calculated with high accuracy. Other systems for measuring the length of a tire footprint are disclosed, for example, in JP 2012-218682 A, EP 2 679 411 A and FR 3 042 281 A. Summary of the Invention [Problem to be solved by the invention]

[0021] The object of the present invention is to overcome the above-mentioned drawbacks and to provide a system and method for measuring the length of the footprint of a tire of a vehicle, in particular an agricultural vehicle, on a ground surface and to be able to evaluate how this length varies as a function of the tire pressure and / or the load applied to the tire.

[0022] The object of the present invention is therefore to provide a system for measuring the length of the footprint of a tire, comprising: a first electronic device that is mounted in use on an inner or outer surface of the tire; a second electronic device that is, in use, in contact with the rim on which the tire is mounted; and a processing device external to these electronic devices, a first reference system x1, y1, z1 is associated with the first electronic device such that axis x1 is a rotational tangent to a first point, which is an attachment point of the first electronic device on the tire, and axis z1 is perpendicular to axis x1; A second reference system x2, y2, z2 is related to the second electronic device such that axis x2 is rotationally tangent to a second point, which is the attachment point of the second electronic device on the rim, and axis z2 is perpendicular to axis x2. The aim is to provide .

[0023] The first electronic device is configured to transmit data to the processing device and includes: a first inertial measurement unit comprising a first gyroscope and a first accelerometer, the first inertial measurement unit being configured to obtain, using the first gyroscope, a plurality of values ​​related to angular velocity about at least a y-axis, or to obtain, using the first accelerometer, a plurality of values ​​related to linear acceleration along at least an x-axis or a plurality of values ​​related to linear acceleration along at least a z-axis; - first storage means for storing data; - the first inertial measurement unit and a first logic control unit connected to the first storage means, from the first inertial measurement unit, ■ Each value of the linear acceleration along the x-axis above, or ■ Each value of the linear acceleration along the z-axis above, or ■ Receive each value of the angular velocity around the y-axis, Using the first digital filter, ■ Filter each value of the linear acceleration along the x-axis to obtain a filtered linear acceleration along the x-axis, or ■ Filter each value of the linear acceleration along the z axis to obtain a filtered linear acceleration along the z axis, or ■ Filter each value of the angular velocity around the y-axis and calculate the y-axis velocity after filtering. Corner Search for speed, a first time corresponding to a first point of contact between a portion of the tire and the ground at which that portion of the tire contacts the ground, and a second time corresponding to a second point of contact between that portion of the tire and the ground beyond which that portion of the tire leaves the ground, each of which is ■ The first and last times of discontinuities in a sine curve related to linear acceleration along the x-axis after filtering, or ■ The first and last times of discontinuities in the sine curve related to the linear acceleration along the z-axis after filtering, or (ii) Identifying a first time and a second time, which are the first time and the last time of a discontinuity in the sine curve related to the angular velocity around the y-axis after the filtering; calculating a time interval between said first time and said second time; storing the first time, the second time, and the time interval in the first storage means; a first logic control unit configured to transmit the first time, the second time, and the time interval to the processing device.

[0024] The second electronic device is configured to transmit data to the processing device and includes: a second inertial measurement unit including a second gyroscope, the second inertial measurement unit being configured to obtain, with the second gyroscope, a plurality of values ​​related to an angular velocity around at least a y-axis; - second storage means for storing data; a second logic control unit connected to said second inertial measurement unit and to said second storage means, receiving a value of angular velocity about the y-axis from the second inertial measurement unit; using a second digital filter to filter each of the values ​​of the angular velocity about the y-axis to obtain each filtered angular velocity about the y-axis; ○ Each time t associated with each value of the angular velocity around the y-axis after the filtering 2y 'Identify ○ At a given time interval, the above filtered angular velocity around the y-axis and each time t 2y ' and stored in the second storage means, ○ Each value of the angular velocity around the y-axis after the above filtering and each time t 2y and a second logic control unit configured to transmit the signal to the processor.

[0025] The processing device is configured to receive at least data from the first electronic device and data from the second electronic device, and includes: - third storage means for storing data; a third logic control unit connected to said third storage means, receiving the first time, the second time, and the time interval from the first electronic device; the filtered values ​​of angular velocity about the y-axis transmitted by the second electronic device and their respective times t 2y ' and receive, ○At each time t within the above time interval 2y Calculate an average value of the filtered angular velocity about the y-axis associated with the second electronic device corresponding to '; The angle between the first axis passing through the tire center and the first tangent point and the second axis passing through the tire center and the second tangent point is calculated using the following formula:

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[0026] Further preferred embodiments of the system are disclosed in the dependent claims.

[0027] The invention also relates to a method for measuring the length of a tire footprint using the system described above.

[0028] The method includes the following steps. A) a plurality of values ​​related to a linear acceleration along an x-axis associated with the first electronic device; or ■ a plurality of values ​​related to a linear acceleration along a z-axis associated with the first electronic device; or obtaining a plurality of values ​​associated with an angular velocity about a y-axis associated with a first electronic device; B) Filter each of the values ​​of linear acceleration along the x-axis to obtain the filtered linear acceleration along the x-axis, or ■ Filter each value of the linear acceleration along the z axis to obtain a filtered linear acceleration along the z axis, or (iii) filtering each value of the angular velocity around the y-axis to obtain a filtered angular velocity around the y-axis; C) a first time at a first point of contact between a portion of the tire and the ground at which the portion of the tire contacts the ground, and a second time at a second point of contact between the portion of the tire and the ground beyond which the portion of the tire leaves the ground, each of which is ■ The first and last times of discontinuities in a sine curve related to linear acceleration along the x-axis after filtering, or ■ The first and last times of discontinuities in the sine curve related to the linear acceleration along the z-axis after filtering, or (ii) identifying a first time and a second time, which are the first time and the last time of a discontinuity in the sine curve related to the angular velocity around the y-axis after the filtering; D) calculating a time interval between the first time and the second time; 、 E ) storing said first time, said second time, and said time interval; F) obtaining a plurality of values ​​related to an angular velocity about at least a y-axis associated with the second electronic device; G) filtering each of the values ​​of the angular velocity about the y-axis to obtain a filtered angular velocity about the y-axis; H) Each time t associated with each value of the angular velocity around the y-axis after filtering 2y ', I) At a given time interval, the above filtered values ​​of the angular velocity around the y-axis and the respective times t 2y '; and storing J ) At each time t within the above time interval 2y calculating an average value of the filtered angular velocity about the y-axis associated with the second electronic device corresponding to K ) The angle between the first axis passing through the tire center and the first tangent point and the second axis passing through the tire center and the second tangent point is calculated using the following formula.

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[0029] The present invention will now be described by way of example and not by way of limitation by way of embodiments thereof and with particular reference to the accompanying drawings in which: [Figure 1]1A and 1B respectively show an agricultural vehicle tire and its footprint when the tire pressure is high, and FIGS. 1C and 1D respectively show an agricultural vehicle tire and its footprint when the tire pressure is low. [Diagram 2] FIG. 2 is a schematic diagram of components of a first embodiment of a system contemplated by the present invention, comprising a first electronic device, a second electronic device and a processing device external to the electronic devices, in which a footprint length is calculated based on information about a linear acceleration along an x-axis associated with the first electronic device. [Diagram 3] FIG. 3A is a perspective view of a wheel including a tire and a rim on which the tire is mounted, showing a first electronic device positioned on the inside of the tire so as to contact the inner surface of the tire itself, a second electronic device positioned in a groove in the rim, and a processing device; FIG. 3B is a side view of the wheel of FIG. 3A, and FIG. 3C is a front view of the wheel of FIG. 3A. [Figure 4] FIG. 4A shows a sine curve on a Cartesian plane representing the linear acceleration along the x-axis associated with a first electronic device when the tire is in use, and FIG. 4B shows a sine curve on a Cartesian plane representing the linear acceleration along the x-axis filtered by a first IIR filter when the tire is in use. [Diagram 5] FIG. 5A shows the trend of two portions of the angular velocity around the y-axis associated with the second electronic device during use of the second electronic device, during a time interval ΔtD, before and after application of a second IIR filter, and FIG. 5B shows the trend of a portion of the angular velocity around the y-axis after filtering, associated with the second electronic device, during the time interval ΔtD, on a Cartesian plane. [Figure 6] FIG. 6 is a schematic diagram showing a tire represented by a circumference, a first axis passing through the center of the tire and a first tangent point between a portion of the tire and the ground, and a length of the tire's footprint substantially equal to the length of a chord for the angle made by the center of the tire and a second axis passing through a second tangent point between the portion of the tire and the ground beyond which the portion of the tire leaves the ground. [Figure 7]FIG. 7A shows a sine curve on a Cartesian plane representing the linear acceleration along the z-axis associated with a first electronic device when the tire is in use, which sine curve relates to a second embodiment of the system of the present invention, the system components of which are the same as those of the system of FIG. 2 (i.e. the first electronic device, the second electronic device and the processing device) and the footprint length is calculated based on information about the linear acceleration along the z-axis, and FIG. 7B shows a sine curve on a Cartesian plane representing the linear acceleration along the z-axis filtered by a first IIR filter when the tire is in use. [Figure 8] FIG. 8A shows a sine curve on a Cartesian plane representing the angular velocity about the y-axis associated with the first electronic device when the tire is in use, which sine curve relates to a third embodiment of the system covered by the present invention, in which the system components are the same as those of the system of FIG. 2 (i.e., the first electronic device, the second electronic device and the processing device) and the footprint length is calculated based on information about the angular velocity about the y-axis. FIG. 8B shows a sine curve on a Cartesian plane representing the angular velocity about the y-axis filtered by the first IIR filter when the tire is in use. [Figure 9] FIG. 9 is a schematic diagram of components of a fourth embodiment of the system covered by the present invention, comprising a first electronic device and a processing device external to the first electronic device. [Figure 10] FIG. 10 shows a sine curve on a Cartesian plane representing the angular velocity about the y-axis filtered by the first IIR filter during use of the tire. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] 2 to 6, a first embodiment of a system for measuring the length of the footprint of a tire 10 is shown. Explain .

[0031] This system is a first electronic device 1 that is mounted on an inner surface 10A or an outer surface 10B of a tire 10 during use; -When in use, 1 tire 0 a second electronic device 2 that is mounted on the rim 20, and in particular, in the disclosed embodiment, is provided in contact with a groove 20A of the rim 20; a processing device 3 external to said electronic devices 1 and 2.

[0032] In the disclosed embodiment, a first reference system x1, y1, z1 is associated with the first electronic device 1 such that its axis x1 is tangent to a rotation circle of a first point P1, which is the mounting point of the first electronic device 1 on the tire 10, and its axis z1 is orthogonal to the axis x1, and a second reference system x2, y2, z2 is associated with the second electronic device 2 such that its axis x2 is tangent to a rotation circle of a second point P2, which is the mounting point of the second electronic device 2 on the rim 20, and its axis z2 is orthogonal to the axis x2.

[0033] The angle between the first axis A1 and the second axis A2 is indicated as α.

[0034] The axes x1 and z1 of the first reference system lie in the same first plane.

[0035] The axes x2 and z2 of the second reference system lie in the same second plane.

[0036] In disclosed embodiments, the second plane is parallel or substantially parallel to the first plane.

[0037] Although not shown, the first plane and the second plane may be the same plane.

[0038] Furthermore, in the disclosed embodiment, the first electronic device 1 is disposed on the inner surface 10A of the tire 10.

[0039] However, the first electronic device may be disposed on the outer surface 10B of the tire 10 without departing from the scope of the present invention.

[0040] The length of the footprint of the tire 10 is calculated based on the angle β between a first axis B1 passing through the center O of the tire 10 and a first contact point CP1 between the portion of the tire 10 and the ground when that portion of the tire 10 contacts the ground, and a second axis B2 passing through the center of the tire and a second contact point CP2 between the portion of the tire 10 and the ground beyond which the portion of the tire 10 leaves the ground (the above contact points are shown in Figure 6).

[0041] In particular, the length of the tire's footprint is substantially defined by a chord relative to said corner, said chord being a chord located within the circumference of the circle representing the tire.

[0042] Regarding the first electronic device 1, the first electronic device 1 has therein: first power supply means 14 for supplying power to the first electronic device 1; a first wireless transceiver module 13 for transmitting and receiving signals / data to and from the processing device 3; a first inertial measurement unit 12 comprising a first accelerometer 122, Using the first accelerometer 122, linear acceleration A along at least the x-axis is measured. 1x (In the embodiment described, the x-axis is Direct Linear acceleration A 1x The values ​​are normalized to unity (i.e., along the x-axis). Direct Linear acceleration A 1x The value of is between -1 and +1. first storage means 15 for storing data, - the first inertial measurement unit a first logic control unit 11 connected to said first radio transceiver module 12, said first radio transceiver module 13 and said first storage means 15, A linear acceleration A along the x-axis from the first inertial measurement unit 12 of the first electronic device 1 1x Receive the value of Using the first digital filter, linear acceleration A along the x-axis is calculated.1x Filter each value of and calculate the linear acceleration along the x-axis after filtering. 1x ', A first time t 1 corresponds to a first contact point CP1 between a part of the tire 10 and the ground, at which the part of the tire 10 comes into contact with the ground. 1,1D and a second time t corresponding to a second contact point CP2 between the portion of the tire 10 and the ground beyond which the portion of the tire 10 separates from the ground. 1,2D Identify the following: The first time t 1,1D and the second time t 1,2D The time interval Δt between D Calculate The first time t 1,1D , the second time t 1,2D , and the time interval Δt D is stored in the first storage means 15, The first time t 1,1D , the second time t 1,2D , and the time interval Δt D and a first logic control unit 11 configured to transmit the signal to the processing device 3.

[0043] In other words, the first contact point CP1 is the initial point of contact between a portion of the tire 10 and the ground, and the second contact point CP2 is the final point of contact between the same portion of the tire 10 and the ground (beyond this second contact point CP2, that portion of the tire 10 leaves the ground).

[0044] Regarding the first digital filter, in the disclosed embodiment, this digital filter is a first IIR filter (Infinite Impulse Response).

[0045] In particular, the first IIR filter has a frequency between 0.1 Hz and 1 Hz. component of Removal It is preferable to do so.

[0046] The first logic control unit 11 determines whether the time interval Δt D can be configured to transmit the signal to the processing device 3.

[0047] Advantageously, energy savings can be achieved by the first electronic device 1 transmitting data to the processing device 3 after a predefined first number of rotations.

[0048] Regarding the first inertial measurement unit, said first inertial measurement unit 12 comprises a first gyroscope 121; Through the first gyroscope 121, at least the angular velocity ω around the y axis is detected. 1y Get ○Top Note Angular velocity around axis ω 1y to the processing device 3.

[0049] FIG. 4A illustrates a linear acceleration A along the x-axis associated with the first electronic device 1 (i.e., the electronic device disposed on the inner surface 10A of the tire 10). 1x 4 shows a sine curve S1 representing

[0050] The sine curve S1 represents the linear acceleration A along the x-axis associated with the first electronic device 1. 1x It shows how this changes over time.

[0051] As can be seen from FIG. 4A, the sinusoidal curve S1 has periodic discontinuities due to portions of the tire 10 first contacting and then lifting off the ground.

[0052] The discontinuities are detected using a first electronic device 1 disposed on the inner surface 10A of the tire 10.

[0053] The sinusoid S filtered by the first IIR filter shown in FIG. 1F is not as pronounced as the sinusoid S1 (i.e., the sinusoid without the first IIR filter applied), but it remains constant over the time interval Δt DIt has the same discontinuity at

[0054] Therefore, this time interval Δt D The duration of is given by the time that said portion of the tire 10 contacts the ground and remains in contact with the ground until that same portion of the tire leaves the ground.

[0055] In use, the tire 10 undergoes multiple revolutions.

[0056] For the first electronic device 1, at a first time t 1,1d and a second time t during which the portion of the tire 10 is still in contact with the ground and beyond which the portion of the tire 10 leaves the ground. 1,2d Two times are identified and stored.

[0057] The rotational motion of the tire 10 is represented by a sine curve, and each of the above-mentioned times is represented by a linear acceleration A along the x-axis, whose abscissa axis represents time and whose ordinate axis represents the first electronic device 1. 1x This corresponds to the intersection point with the abscissa axis of the Cartesian plane.

[0058] In the example described, the storage means 15 stores the first logic system Your Located outside of Knit 11.

[0059] However, the first storage means 15 may also be included in the first logic control unit 11 without departing from the scope of the present invention.

[0060] In particular, with regard to the second electronic device 2, as already mentioned, in the disclosed embodiment, the second electronic device 2 is disposed in a groove 20A of the rim 20.

[0061] However, the second electronic device 2 may be located anywhere on the rim 20, for example on the outer or outward facing surface of the rim or on the disc of the rim, without departing from the scope of the invention.

[0062] The second electronic device 2 has therein: second power supply means 24 for supplying power to the second electronic device 2; a second wireless transceiver module 23 for transmitting and receiving signals / data to and from the processing device 3; a second inertial measurement unit 22 comprising a second gyroscope 221, Through the second gyroscope 221, at least the angular velocity ω around the y axis is detected. 2y a second inertial measurement unit (22) configured to obtain a plurality of values ​​related to second storage means 25 for storing data, a second logic control unit 21 connected to said second inertial measurement unit 22, to said second radio transceiver module 23 and to said second storage means 25, The angular velocity ω around the y-axis is measured from the second inertial measurement unit 22. 2y Receive the value of ○The angular velocity ω around the y-axis is calculated using the second digital filter. 2y Filter each value of and calculate the angular velocity around the y-axis after filtering. 2y ', ○ Angular velocity ω around the y-axis after the above filtering 2y Each time t associated with each value of ' 2y 'Identify ○ At a given time interval, the angular velocity ω around the y-axis after the above filtering 2y ' values ​​and their respective times t 2y ' and stored in the second storage means 25, Filtering the above Later Angular velocity ω around the y-axis 2y ' values ​​and their respective times t 2y and a second logic control unit 21 configured to transmit the signal ``'' to the processing device 3.

[0063] Regarding the second digital filter, in a disclosed embodiment, the second digital filter is a second IIR filter.

[0064] In particular, the second IIR filter has frequencies between 0.1 Hz and 1 Hz. component of Removal It is preferable to do so.

[0065] Angular velocity ω around the y-axis after filtering 2y ' and their respective times t 2y The step of storing may be performed at predetermined time intervals, which may be selected such that the storing step is periodic.

[0066] Regarding the second inertial measurement unit 22, the second inertial measurement unit 22 comprises a second accelerometer 222; Through the second accelerometer 222, linear acceleration A along at least the x-axis 2x Get multiple values ​​related to ○Linear acceleration A along the x-axis 2x to the processing device 3.

[0067] The second logic control unit 21 outputs the filtered angular velocity around the y-axis after the tire 10 has completed a second predetermined number of rotations. degree ω 2y ' value and the angular velocity around the y-axis after filtering degree ω 2y Each time t associated with each value of ' 2y ' and to the processing device 3.

[0068] Advantageously, energy savings can be achieved by the second electronic device 2 transmitting data to the processing device 3 after a second predetermined number of rotations.

[0069] Regarding the digital filters, and in particular the IIR filters mentioned above, these IIR filters make it possible to eliminate noises mainly due to vibrations, mechanical transmission and ground irregularities.

[0070] With regard to both electronic devices 1 and 2 of the system, each electronic device 1, 2 is fixed to the tire 10 and rim 20, respectively, by means of respective fixing devices (not shown) that are dust and water resistant.

[0071] In particular, with regard to the processing device 3, the processing device 3 includes therein: third power supply means 34 for supplying power to the processing device 3; a third wireless transceiver module 33 for transmitting and receiving signals / data to the first electronic device 1 and to the second electronic device 2; third storage means 35 for storing data, a third logic control unit 31 connected to said third radio transceiver module 33, to said third power supply means 34 and to said third storage means 35, The first electronic device 1 transmits the first time t 1,1D and the second time t 1,2D and the time interval Δt D And receive, ○ From the second electronic device 2, the angular velocity ω around the y-axis after the filtering is 2y ' and the filtered angular velocity around the y-axis ω 2y Each time t associated with each value of ' 2y ' and receive, ○The above time interval Δt D At each time t 2y ' the average value of the angular velocity about the y-axis after filtering associated with the second electronic device 2

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[0072] As can be seen from the drawing, the footprint length is substantially the distance between the first axis B1 (i.e., the center of the tire and the tire 10 Part of and the ground) and a second axis B2 (i.e., an axis passing through the center of the tire and the second point of contact CP2 between that portion of the tire 10 and the ground).

[0073] FIG. 6 is a schematic diagram of a tire 10 represented by a circumference having a center O and a rolling radius R0, where the angle β is the angle between a first axis B1 (passing through the center of the tire and a first tangent point CP1) and a second axis B2 (passing through the center of the tire and a second tangent point CP2).

[0074] As can be seen from FIG. 6, the length of the tire footprint is approximated by the length of the chord for the angle (defined by the first axis B1 and the second axis B2) connecting the first contact point CP1 and the second contact point CP2.

[0075] Furthermore, the first electronic device 1 may comprise a first clock source 16 connected to the first logic control unit 11, and the second electronic device 2 may comprise a second logic Control Unit Ni T2 1 and the processing device 3 may be provided with a third clock source 36 connected to the third logic control unit.

[0076] In the second embodiment to be described, unlike the first embodiment, the first inertial measurement unit 12 included in the first electronic device 1 is Through the first accelerometer 122, at least along the z-axis Direct Linear acceleration A 1z The method is configured to obtain

[0077] Therefore, the first logic system Your Knit 11 is From the first inertial measurement unit 12 of the first electronic device 1, Also Linear acceleration along axis A 1z Receive the value of ○The first digital filter Also Linear acceleration along axis A 1z Filter the value of to obtain the filtered linear acceleration along the z-axis A 1z ', A first point of contact CP1 between a portion of the tire 10 and the ground, a first time t 1,1D and a second point of contact CP2 between the portion of the tire 10 and the ground beyond which the portion of the tire 10 separates from the ground. 1,2D Identify the following: The first time t 1,1D and the second time t 1,2D The time interval Δt between D Calculate The first time t 1,1D , the second time t 1,2D , and the time interval Δt D is stored in the first storage means 15, The first time t 1,1D , the second time t 1,2D , and the time interval Δt D to the processing device 3. The device is configured to obtain

[0078] FIG. 7A shows the linear acceleration A along the z axis associated with the first electronic device 1 (i.e., the electronic device disposed on the inner surface 10A of the tire 10) in the second embodiment. 1z 4 shows a sine curve S1' representing

[0079] The sinusoidal curve S1′ represents the linear acceleration along the z-axis associated with the first electronic device 1. A1Z It shows how this changes over time.

[0080] As can be seen from FIG. 7A, the sinusoidal curve S1' periodically has discontinuities due to portions of the tire 10 first contacting the ground and then lifting off the ground.

[0081] Figure 7B shows S 1F The sinusoid filtered by the first digital filter, denoted by ', is represented as sinusoid S1' (i.e., the first digital fill Ta Although not as pronounced as the sinusoidal curve without the application of D , which has the same discontinuity.

[0082] Regarding the second electronic device 2, the operation of the second electronic device 2 is the same as that of the second electronic device described in the first embodiment.

[0083] Regarding the processing device 3, the operation of the processing device 3 is the same as that of the processing device 3 described in the first embodiment.

[0084] In the third embodiment, unlike the first and second embodiments, at the first time t 1,1D and the second time t 1,2D The time interval Δt between D is the angular velocity ω about the y-axis associated with the first electronic device 1. 1y It is calculated by the value of

[0085] Therefore, the first The argument Reason control Unit 11: The first inertial measurement unit 12 of the first electronic device 1 measures the angular velocity ω around the y-axis. 1y Receive the value of The first digital filter calculates the angular velocity ω around the y-axis. 1y Filter the value of and calculate the filtered angular velocity around the y-axis ω 1y ', At a first contact point CP1 between a portion of the tire 10 and the ground, the portion of the tire 10 comes into contact with the ground. The Time t of 1 1,1D and a second point of contact CP2 between the portion of the tire 10 and the ground beyond which the portion of the tire 10 separates from the ground. 1,2D Identify the following: The first time t 1,1D and the second time t 1,2D The time interval Δt between D Calculate The first time t 1,1D , the second time t 1,2D , and the time interval Δt D The first Notes storing the information in a storage means; The first time t 1,1D , the second time t 1,2D , and the time interval Δt D to the processing device 3.

[0086] 8A and 8B show a sinusoidal curve S1″ that is not filtered by the first digital filter and a sinusoidal curve S1″ that is filtered by the first digital filter, which represent an angular velocity about the y-axis associated with the first electronic device 1 (the third embodiment described above). 1F '' and are shown on the Cartesian plane.

[0087] As can be seen from FIG. 8A, the sinusoidal curve S1'' periodically has discontinuities due to portions of the tire 10 first contacting and then lifting off the ground.

[0088] The sinusoidal curve S filtered by the first digital filter shown in FIG. 1F '' is not as pronounced as the sinusoid S1'' (i.e., the sinusoid to which the first digital filter is not applied), but it remains constant over the time interval Δt D It has the same discontinuity at

[0089] The above time interval Δt Dis the angular velocity around the y-axis after filtering, ω 1y ' is the largest (ω MAX The first time t 1,1D And after filtering y Angular velocity around axis ω 1x ' is the smallest (ω MIN At the second time t 1,2D It is defined by:

[0090] Regarding the second electronic device 2, the operation of the second electronic device 2 is the same as that of the second electronic device described in the first embodiment.

[0091] Regarding the processing device 3, the operation of the processing device 3 is the same as that of the processing device 3 described in the first embodiment.

[0092] For the three embodiments described above, the time interval Δt D is the first time t, which can be one of the following depending on the embodiment applied: 1,1D and the second time t 1,2D It is defined by: ■ Linear acceleration A along the x-axis after filtering 1x ' (see the first embodiment) 1F The first and last times of the discontinuity in ■ After filtering Z Linear acceleration along axis A 1z ' (see the second embodiment) 1F The first and last times of the discontinuity in ■ Angular velocity ω around the y-axis after filtering 1y ' (see the third embodiment) 1F '' The first and last times of the discontinuity.

[0093] Furthermore, for each of the three embodiments described above, the third logic control unit 31 of the processing device 3 - may be configured to send a synchronization signal to the first electronic device 1 and the second electronic device 2 to synchronize their respective clock sources to the third clock source 36 of the processing device 3, depending on a predetermined time resolution that may be required depending on the circumstances.

[0094] The synchronization signal is preferably transmitted periodically, for example, when the tire 10 has completed a predetermined number of revolutions.

[0095] If each of the electronic devices is configured only to transmit data to the processing device 3 and the processing device 3 is configured to receive and process such data, then transmission of a synchronization signal is not necessary.

[0096] In a variant in which each electronic device 1, 2 is configured only to acquire, filter and transmit data to the processing device 3, which is configured to receive and process such data to calculate the footprint length, a first wireless transmitting module is used instead of the first wireless transceiver module (located in the first electronic device 1), a second wireless transmitting module is used instead of the second wireless transceiver module (located in the second electronic device 2), and a wireless receiving module is used instead of the third wireless transceiver module (located in the processing device 3).

[0097] As is apparent from the above, each electronic device 1, 2 may be configured to acquire and transmit data (after filtering) and the processing device 3 may be configured to receive and process such data in order to calculate the tire footprint length, each electronic device 1, 2 may be configured to acquire and transmit data (after filtering) and receive one or more signals (e.g. synchronization signals, etc.) from the processing device, and the processing device 3 may be configured to receive and process such data in order to calculate the footprint length and transmit one or more signals (e.g. synchronization signals, etc.) to each of said electronic devices.

[0098] Furthermore, for each of the three embodiments described above, the system may consist of a first electronic device 1, a second electronic device 2 and a processing device 3.

[0099] In the fourth embodiment shown in FIG. 9, the system comprises a first electronic device 1 and a processing device 3 .

[0100] In this fourth embodiment, the role of the second electronic device 2 is taken by the first electronic device 1, ie an electronic device arranged on the inner surface 10A of the tire 10.

[0101] Therefore, the time interval Δt D and angular velocity about the y-axis are obtained through a single electronic device, namely, an electronic device mounted on the inner surface 10A of the tire 10.

[0102] Therefore, unlike the three embodiments described above, in the fourth embodiment the system comprises only a single electronic device, i.e. the first electronic device 1, located inside the tire 10, and a processing device 3 external to this first electronic device 1.

[0103] The first electronic device 1 is configured to acquire and filter data and transmit signals / data to the processing device 3, which is configured to receive the transmitted signals / data and process such data.

[0104] Therefore, the first electronic device 1 can be used not only to identify a first time and a second time and calculate the time interval between the two times, but also to obtain values ​​of angular velocity around the y axis associated with the first electronic device 1 and their respective times in order to calculate the angle β.

[0105] Therefore, the filtered angular velocity ω about the y-axis associated with the second electronic device 2 in each of the above embodiments is 2y' is the filtered angular velocity ω about the y-axis associated with the first electronic device 1 in the previous embodiments, i.e., the only electronic device in this fourth embodiment; 1y ' is equivalent to '.

[0106] Therefore, in the fourth embodiment, the filtered angular velocity around the y axis (over the time interval Δt D (at each time in

number

number

[0107] FIG. 10 shows the angular velocity ω about the y-axis after filtering of the first sole electronic device 1. 1y ' represents the sine curve S 1F ''' is shown on the Cartesian plane.

[0108] As in the third embodiment, the sinusoidal curve S filtered by the first digital filter shown in FIG. 1F ''' is the angular velocity around the y-axis after filtering, ω 1y ' is the largest (ω MAX The first time t 1,1D and the angular velocity around the y-axis after filtering, ω 1y ' is the smallest (ω MIN At the second time t 1,2D The time interval Δt D There is a discontinuity corresponding to

[0109] In this fourth embodiment, the average value of the angular velocity around the y axis

number

[0110] With reference to FIG. 10, the average value can be calculated by the following formula:

number

[0111] Alternatively, the system may consist of said first electronic device 1 and said processing device 3 .

[0112] The fourth embodiment is preferable because the system structure is simplified compared to the system structures described in the above embodiments.

[0113] Furthermore, the energy consumption of the above system is lower than that of the systems described with respect to the previous embodiments.

[0114] Regarding the second embodiment (FIGS. 7A and 7B), the third embodiment (FIGS. 8A and 8B) and the fourth embodiment (FIGS. 9 and 10), the first digital filter is a first IIR filter (infinite impulse response) as described in the first embodiment above.

[0115] This is also evident from the text of the figures (described in the brief description of the drawings) associated with each embodiment.

[0116] The present invention also relates to a method for measuring the length of the footprint of a tire 10 using the system described above.

[0117] The method includes the following steps. A) Linear acceleration A along the x-axis associated with the first electronic device 1 1x or ■ Linear acceleration A along the z-axis associated with the first electronic device 11z or ■ Angular velocity ω about the y-axis associated with the first electronic device 1 1y obtaining a plurality of values ​​associated with B) ■ Linear acceleration A along the x-axis 1x Filter each value of x to obtain the filtered linear acceleration A along the x-axis. 1x ' or ■ Linear acceleration A along the z-axis 1z Filter each value of and calculate the filtered linear acceleration along the z-axis, A 1z ' or ■Angular velocity ω around the y-axis 1y Filter each value of and calculate the filtered angular velocity around the y-axis ω 1y ', C) A first point of contact CP1 between a portion of the tire 10 and the ground, a first time t at which the portion of the tire 10 contacts the ground. 1,1D and a second point of contact CP2 between the portion of the tire 10 and the ground beyond which the portion of the tire 10 separates from the ground. 1,2D and each of them is, ■ Linear acceleration A along the x-axis after the above filtering 1x 'The sine curve S associated with 1F The first and last times of the discontinuity, or ■ Linear acceleration A along the z-axis after the above filtering 1z 'The sine curve S associated with 1F ' discontinuity, or ■ Angular velocity ω around the y-axis after the above filtering 1y 'The sine curve S associated with 1F The first time t 1,1D and the second time t 1,2D and D) The first time t 1,1D and the second time t 1,2D The time interval Δt between Dand calculating E) The first time t 1,1D , the second time t 1,2D , and the time interval Δt D storing the F) Angular velocity ω about at least the y-axis associated with the second electronic device 2 2y obtaining a plurality of values ​​associated with G) Angular velocity ω around the y-axis 2y Filter each value of and calculate the angular velocity around the y-axis after filtering. 2y ', H) Angular velocity ω around the y-axis after the above filtering 2y Each time t associated with each value of ' 2y ', I) At a given time interval, the angular velocity ω around the y-axis after the above filtering 2y ' and each time t 2y '; and storing J ) the above time interval Δt D At each time t 2y ', the average value of the angular velocity around the y-axis after filtering associated with the second electronic device 2 corresponding to

number

number

number

[0118] For each embodiment of the system described above, the value obtained is the linear acceleration A of the first electronic device 1 along the x-axis. 1x (see the first embodiment of the system), or the linear acceleration A along the z-axis of the first electronic device 1 1z (see the second embodiment of the system), or the angular velocity ω of the first electronic device 1 about the y axis 1y is a value related to

[0119] Therefore, the above filtering step and the above first time t 1,1D and the second time t 1,2D The time interval Δt between D The first time t used to calculate 1,1D and the second time t 1,2D The steps of determining whether and how much is the true value are performed on values ​​obtained using one of the first three embodiments of the system described above.

[0120] In a fourth embodiment, in which the first electronic device 1 plays the role of the second electronic device 2, the steps of determining the first and second times, calculating the time interval between the two times and obtaining values ​​of the angular velocity around the y axis associated with the first electronic device 1 and their respective times in order to calculate the angle β are performed by a single electronic device, i.e. the first electronic device 1, and the same considerations apply as already stated above in relation to this fourth embodiment. [Industrial Applicability]

[0121] As already mentioned, the present system and method have the advantage that it makes it possible to measure the length of the footprint of a tire, which is the object of the present invention.

[0122] It is therefore possible to monitor the footprint length over time and monitor whether the value of the footprint length changes over time due to, for example, changes in tire pressure and / or load on the tire.

[0123] Although the present invention has been described in terms of preferred embodiments thereof, for purposes of illustration and not limitation, it is to be understood that variations and / or modifications may be effected by those skilled in the art without departing from the scope of the invention as defined by the appended claims.

Claims

1. A system for measuring the length of a footprint of a tire (10), comprising: a first electronic device (1) mounted, in use, on the inner surface (10A) or on the outer surface (10B) of said tire (10); a second electronic device (2) that, in use, is placed in contact with the rim (20) on which said tire (10) is mounted; a processing device (3) external to these electronic devices (1, 2), First reference system x １ , y １ , z １ is the axis x １ is tangential to the rotation of a first point (P1), which is the mounting point of the first electronic device (1) on the tire (10), and is aligned along an axis z １ is the axis x １ orthogonally associated with the first electronic device (1); Second reference system x ２ , y ２ , z ２ is the axis x ２ is tangential to the rotation of a second point (P2), which is the attachment point of the second electronic device (2) on the rim (20), and is aligned with an axis z ２ is the axis x ２ orthogonally associated with the second electronic device (2); The first electronic device (1) is configured to transmit data to the processing device (3) and includes therein: - a first gyroscope (121) and a first accelerometer (122), said first gyroscope (121) being used to measure at least an angular velocity (ω １ｙ ) or by using the first accelerometer (122) to obtain a plurality of values ​​related to linear acceleration (A １ｘ ) or at least a number of values ​​related to the linear acceleration (A １ｚ a first inertial measurement unit (12) configured to obtain a plurality of values ​​related to a - first storage means (15) for storing data, a first logic control unit (11) connected to said first inertial measurement unit (12) and to said first storage means (15), from the first inertial measurement unit (12), ■ The linear acceleration along the x-axis (A １ｘ ) or Linear acceleration along the z-axis (A １ｚ ) or ■ The angular velocity around the y-axis (ω １ｙ ) values, Using a first digital filter, ■ The linear acceleration along the x-axis (A １ｘ ) to obtain the filtered linear acceleration along the x-axis (A １ｘ ') or Linear acceleration along the z-axis (A １ｚ ) to obtain the filtered linear acceleration along the z-axis (A １ｚ ') or ■ The angular velocity around the y-axis (ω １ｙ ) is filtered to obtain the filtered angular velocity around the y-axis (ω １ｙ ') and a first time (t ) at which a portion of the tire (10) comes into contact with the ground, which corresponds to a first contact point (CP1) between said portion of the tire (10) and the ground; １，１Ｄ ) and a second time (t ) corresponding to a second contact point (CP2) between the portion of the tire (10) and the ground beyond which the portion of the tire (10) leaves the ground. １，２Ｄ ), each of which is The linear acceleration (A) along the x-axis after filtering １ｘ The sine curve (S １Ｆ ) are the first and last times of a discontinuity, or The linear acceleration (A) along the z-axis after filtering １ｚ The sine curve (S １Ｆ') are the first and last times of a discontinuity, or ■ The angular velocity (ω １ｙ The sine curve (S １Ｆ The first time (t ) is the first time and the last time of the discontinuity of １，１Ｄ ) and the second time (t １，２Ｄ ) and The first time (t １，１Ｄ ) and the second time (t １，２Ｄ ) the time interval (Δt Ｄ ) is calculated, The first time (t １，１Ｄ ), the second time (t １，２Ｄ ), and the time interval (Δt Ｄ ) in the first storage means (15); The first time (t １，１Ｄ ), the second time (t １，２Ｄ ), and the time interval (Δt Ｄ a first logic control unit (11) configured to transmit a signal to the processing device (3); The second electronic device (2) is configured to transmit data to the processing device (3) and has therein: a second inertial measurement unit (22) comprising a second gyroscope (221), by means of which the angular velocity (ω) around at least the y-axis is measured; ２ｙ a second inertial measurement unit (22) configured to obtain a plurality of values ​​related to the - second storage means (25) for storing data, a second logic control unit (21) connected to said second inertial measurement unit (22) and to said second storage means (25), ○ The angular velocity (ω) around the y-axis is measured from the second inertial measurement unit (22). ２ｙ ) value, ○ Using a second digital filter, the angular velocity around the y-axis (ω ２ｙ ) and calculate the angular velocity around the y-axis after filtering (ω ２ｙ ') and ○ The angular velocity around the y-axis after the filtering (ω ２ｙ Each time t ' ２ｙ 'Identify At a given time interval, the filtered angular velocity around the y-axis (ω ２ｙ ') and each time t ２ｙ ' is stored in the second storage means (25), ○ The angular velocity around the y-axis after the filtering (ω ２ｙ ') and each time t ２ｙ and a second logic control unit (21) configured to transmit the signal to the processing device (3), The processing device (3) is configured to receive at least data from the first electronic device (1) and data from the second electronic device (2), and includes therein: - third storage means (35) for storing data, a third logic control unit (31) connected to said third storage means (35), The first time (t １，１Ｄ ), the second time (t1, 2D), and the time interval (Δt Ｄ ) from the first electronic device (1); The filtered angular velocity around the y-axis (ω ２ｙ ') and their respective times t ２ｙ ' and receive The time interval (Δt Ｄ ) at each time t ２ｙ ', the average value of the angular velocity around the y-axis after filtering associated with the second electronic device (2) corresponding to ##EQU00015## ) is calculated, The angle (β) between a first axis (B1) passing through the center (O) of the tire (10) and the first tangent point (CP1) and a second axis (B2) passing through the center (O) of the tire (10) and the second tangent point (CP2) is calculated by the following formula: ##EQU00016## Calculate according to The length of the footprint of the tire (10) is calculated by the following formula: ##EQU00017## (In the formula, R ０ is the rolling radius of the tire (10).

2. The first logic control unit (11) of the first electronic device (1) determines whether the time interval (Δt Ｄ ) to said processing device (3), The second logic control unit (21) of the second electronic device (2) detects the filtered angular velocity (ω) around the y-axis when the tire (10) has completed a second predetermined number of rotations. ２ｙ ') and their respective times t ２ｙ 2. The system according to claim 1, characterized in that it is adapted to transmit to the processing device (3).

3. the first digital filter is a first IIR filter that removes frequency components between 0.1 Hz and 1 Hz; 3. The system of claim 1, wherein the second digital filter is a second IIR filter that removes frequency components between 0.1 Hz and 1 Hz.

4. the first electronic device (1) is configured to receive one or more signals from the processing device (3) and is provided with a first clock source (16) connected to the first logic control unit (11); the second electronic device (2) is configured to receive one or more signals from the processing device (3) and is provided with a second clock source (26) connected to the second logic control unit (21); the processing device (3) is configured to transmit one or more signals to each of the electronic devices (1, 2) and is provided with a third clock source (36) connected to the third logic control unit (31); The third logic control unit (31) A system according to any one of claims 1 to 3, characterized in that it is configured to send a synchronization signal to the first electronic device (1) and the second electronic device (2) in order to synchronize the first clock source (16) and the second clock source (26) to the third clock source (36).

5. 5. The system according to claim 4, characterized in that the third logic control unit (31) of the processing device (3) is configured to transmit the synchronization signal when the tire (10) has completed a predetermined number of revolutions.

6. The role of the second electronic device (2) is played by the first electronic device (1), so that the angular velocity (ω) around the y-axis after filtering of the second electronic device (2) is ２ｙ The value of ω′) is calculated based on the filtered angular velocity (ω) of the first electronic device (1) about the y-axis. １ｙ ') and the time interval (Δt Ｄ ) the average value ( [0018] ) is the time interval (Δt Ｄ ) the average value ( [0019] 4. The system according to claim 1, wherein the first and second inputs are replaced by the second and third inputs.

7. The time interval (Δt Ｄ ) is the angular velocity (ω) around the y-axis after filtering １ｙ The first time (t １，１Ｄ) and the angular velocity around the y-axis after filtering (ω １ｙ The second time (t １，２Ｄ ) and the average value of the angular velocity ( [0020] 4. The system of claim 1, wherein the filtered angular velocity about the y-axis (ω 1y ') is given by dividing the sum of the maximum value of the filtered angular velocity about the y-axis (ω 1y ') by two.

8. A method for measuring a footprint length of a tire (10) using a system according to any one of claims 1 to 7, comprising: A) Linear acceleration along the x-axis associated with the first electronic device (1) (A １ｘ ) or Linear acceleration (A) along the z-axis associated with the first electronic device (1) １ｚ ) or Angular velocity (ω) around the y-axis associated with the first electronic device (1) １ｙ deriving a plurality of values ​​associated with the B) Linear acceleration along the x-axis (A １ｘ ) to obtain the filtered linear acceleration along the x-axis (A １ｘ ') or Linear acceleration along the z-axis (A １ｚ ) to obtain the filtered linear acceleration along the z-axis (A １ｚ ') or ■ The angular velocity around the y-axis (ω １ｙ ) is filtered to obtain the filtered angular velocity around the y-axis (ω １ｙ ') and C) a first point of contact (CP1) between a portion of the tire (10) and the ground, a first time (t １，１Ｄ) and a second time (t t ) at a second contact point (CP2) between the portion of the tire (10) and the ground beyond which the portion of the tire (10) leaves the ground. １，２Ｄ ), each of which is The linear acceleration (A) along the x-axis after filtering １ｘ The sine curve (S １Ｆ ) are the first and last times of a discontinuity, or The linear acceleration (A) along the z-axis after filtering １ｚ The sine curve (S １Ｆ ') are the first and last times of a discontinuity, or ■ The angular velocity (ω １ｙ The sine curve (S １Ｆ The first time (t ) is the first time and the last time of the discontinuity of １，１Ｄ ) and the second time (t １，２Ｄ ) D) the first time (t １，１Ｄ ) and the second time (t １，２Ｄ ) the time interval (Δt Ｄ ) and E) the first time (t １，１Ｄ ), the second time (t １，２Ｄ ), and the time interval (Δt Ｄ ) storing the F) an angular velocity (ω) about at least the y-axis associated with the second electronic device (2); ２ｙ deriving a plurality of values ​​associated with the G) Angular velocity (ω) around the y-axis ２ｙ ) and calculate the angular velocity around the y-axis after filtering (ω ２ｙ ') and H) Each time instant t associated with each value of the angular velocity about the y-axis after filtering ２ｙ ', I) At a predetermined time interval, the filtered angular velocity (ω ２ｙ') and each time t ２ｙ '; and storing J) the time interval (Δt Ｄ ) at each time t ２ｙ ', the average value of the angular velocity around the y-axis after filtering associated with the second electronic device (2) corresponding to ##EQU00021## ) and K) The angle (β) between a first axis (B1) passing through the center (O) of the tire (10) and a first contact point (CP1) and a second axis (B2) passing through the center (O) of the tire (10) and a second contact point (CP2) is calculated using the following formula: [0022] and calculating the L) The length of the footprint of the tire (10) is calculated by the following formula: [0023] (In the formula, R ０ is the rolling radius of the tire (10).

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