Method for estimating load distributed on trailer connected to vehicle

Abstract

Disclosed is a method for estimating a change in a load borne by a tire wheel assembly on a trailer resulting from attachment of the trailer to a stationary towing vehicle, the method comprising the steps of: attaching the trailer to a vehicle; recording an internal pressure P in a fluid chamber of the tire wheel assembly equipped with the pressure sensor; determining an internal temperature T in the fluid chamber of the tire wheel assembly equipped with the pressure sensor using the specified variation rule; evaluating, by means of the recorded internal pressure P and the determined internal temperature T, a change in volume [Delta] V of the tire-wheel assembly equipped with the pressure sensor using a model of a fluid undergoing an adiabatic transition, the fluid having a desired gas behavior; the variation [delta] Z in the load borne by the n tire wheel assemblies equipped with pressure sensors is estimated using a second function, the parameters of which include the intermediate variation [delta] V in the evaluated volume and the flattening stiffness KP per unit volume of the tires of the tire wheel assemblies.

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of real-time determination of applied quasi-static loads, in particular to the variation of the load generated by the connection of a trailer to a vehicle, especially when the vehicle is not moving. BACKGROUND

[0002] Obtaining the quasi-static load applied to a trailer that is not moving makes it possible to determine whether the trailer or each of the trailer axles is in a safe state even before the trailer is started, thus improving reliability and meeting road traffic safety requirements. In particular, determining the load applied to an inflation system such as a tire wheel assembly generally requires a balance weight and it is very difficult to determine this load outside very specific loading sites, for example quarries where trailers connected to a vehicle are loaded. To assess the load borne by a trailer and by each of the trailer axles outside these specific locations, it is possible to assess the load borne by each of the tire wheel assemblies of the trailer by the footprint left by the tire on the ground. Although it is possible to measure using a system that quantifies the static pressure by inserting a measurement system between the tire wheel assembly and the ground, this is not a simple task and the accuracy of the measurement depends on the correct positioning of the measurement system. Another alternative is to assess the size of the footprint in driving conditions by measuring the deformation of the tire as the wheel turns, thus determining the size of the footprint. By means of a mathematical model that relates the type of tire, the inflation pressure and the external dimensions of the footprint, it is possible to deduce the load applied to the tire casing. Unfortunately, this measurement is made in driving conditions. Thus, when the measurement is made, the trailer can no longer be in its safe operating range. Furthermore, for very heavy loads, achieving the accuracy of these measurements becomes tricky, as the deformation of the tire that determines the variation of the load tends to stabilize in the circumferential direction, while the deformation of the tire casing that is measured generally falls in this circumferential direction.

[0003] The subject and method of the present invention aim to solve the problem of measuring the variation of the load borne by a trailer without a measurement system outside the trailer, i.e. that can be used at any time without the need for specific measurement devices. Furthermore, this assessment is made at rest so that it is possible to declare whether the trailer has been safely loaded before it starts moving. SUMMARY

[0004] The present invention relates to a method for estimating the variation of the load borne by the tire wheel assemblies of a trailer resulting from the connection of the trailer to a stationary towing vehicle, said method comprising the following steps: • in a preliminary phase, i.e. before the trailer is connected to the vehicle: • at least one pressure sensor is provided for at least one tire wheel assembly of at least one axle of the trailer not connected to the towing vehicle, said sensor being able to measure the internal pressure of the fluid cavity of the tire wheel assembly defined by the tire casing and the wheel, preferably at least one pressure sensor is provided for at least one tire wheel assembly of each axle of the trailer, very preferably at least one pressure sensor is provided for all tire wheel assemblies of all axles of the trailer; • determining an initial load Z1 applied to at least one pressure sensor-equipped tire wheel assembly of the trailer not connected; • determining an initial inflation pressure P1 of at least one pressure sensor-equipped tire wheel assembly of the trailer; • determining an initial internal temperature T1 of at least one pressure sensor-equipped tire wheel assembly of the trailer; • evaluating the initial volume V1 of at least one pressure sensor-equipped tire wheel assembly with a first function whose parameters include the volume V0 of the fluid cavity of the tire wheel assembly empty and inflated to the initial pressure P1 and the flattening rigidity K of the tire of the tire wheel assembly per unit volume P ; • evaluating the number of moles n of fluid in the fluid cavity of each pressure sensor-equipped tire wheel assembly with a model taking into account the inflation pressure P1, the initial volume V1 and the temperature T1 ; • determining the evolution law of the internal temperature T of the fluid cavity as a function of the internal pressure P during the adiabatic transition of at least one tire wheel assembly inflated and bearing a load Z1 and equipped with at least one pressure sensor; • during the main phase: • connecting the trailer to the vehicle at a geometric point M of the trailer; • recording the internal pressure P of the fluid cavity of at least one pressure sensor-equipped tire wheel assembly at a collection frequency F1 ; • determining the internal temperature T of the fluid cavity of at least one pressure sensor-equipped tire wheel assembly with the evolution law determined during the preparatory phase; • evaluating the intermediate change in volume AV of at least one pressure sensor-equipped tire wheel assembly by using a model of the fluid, said fluid behaving as an ideal gas, undergoing an adiabatic transition, by using the recorded internal pressure P and the determined internal temperature T; • estimating the change in load AZ borne by each pressure sensor-equipped tire wheel assembly by using a second function whose parameters include the evaluated intermediate change in volume AV and the flattening rigidity K of the tire per unit volume P .

[0005] According to a preferred embodiment, in the preliminary phase, at least one tyre wheel assembly of at least one axle of the trailer equipped with a pressure sensor comprises a temperature sensor able to measure the temperature of the fluid chamber, the method comprising, in the main phase, the step of recording the internal temperature T of the fluid chamber of at least one tyre wheel assembly equipped with a pressure sensor at a collection frequency F2, the method comprising a second step of evaluating the intermediate variation AV2 of the volume of at least one tyre wheel assembly equipped with a pressure sensor, using a model of the fluid as an ideal gas, in thermal equilibrium with the environment outside the fluid chamber, taking into account the recorded internal temperature T.

[0006] The method for determining the variation of the applied load comprises two successive phases. The first phase comprises identifying the intrinsic parameters of the tyre wheel assembly before the trailer is connected to the vehicle. This constitutes establishing a measurement system of the trailer by installing a measurement system on the axles of the trailer and identifying the initial parameters of the tyre wheel assembly, for example the volume of the fluid chamber, the quantity of fluid contained in the closed volume defined by the fluid chamber, the load initially applied to the tyre wheel assembly by the unconnected trailer, the internal temperature of the fluid chamber of each tyre wheel assembly and the inflation pressure of the fluid chamber. Intuitively, in estimating the quantity of fluid trapped in the fluid chamber, it is assumed that the properties of the fluid are known. It is also necessary to have an evolution law that links the relevant variation of the internal temperature T of the tyre wheel assembly to the variation of the inflation pressure P of the tyre wheel assembly when the tyre wheel assembly is in working conditions, in particular, under a load Z1, around an inflation pressure P1 and a temperature T1. This evolution law can be a default law or can be derived from experimental characteristics or numerical simulations of the relevant tyre wheel assembly.

[0007] The second phase represents the step of evaluating the variation of the load applied to each of the tyre wheel assemblies equipped with the electronic device due to the connection of the trailer to the vehicle. The electronic device, comprising a pressure sensor, manages and regulates the recording of the pressure measurements. Thus, when the trailer is connected to the vehicle, the inflation pressure of the fluid chamber of each of the tyre wheel assemblies equipped with the electronic device is recorded. During the transient phase, the time evolution of the physical quantities related to the fluid chamber is greater. The connection of the trailer induces a first transition corresponding to the work produced by the additional load, which can be similar to an adiabatic (i.e. fast) transition, which has a dominant effect compared to the second transition. Then, after the fast transition, there is a slower transition corresponding to the thermal equilibrium of the fluid chamber through the tyre casing and the wheel with the external environment. This equilibrium is necessary after the internal temperature change of the fluid chamber related to the work. This thermal equilibrium is established more slowly due to the thermal inertia of the tyre and the wheel. Moreover, the effect of the thermal equilibrium on the variation of the volume of the fluid chamber is less important compared to the transition related to the work. Thus, different sampling frequencies can be used for the two physical quantities, temperature and pressure. However, the same sampling frequency can also be used for the two sensors. Preferably, the electronic device is fixed to the internal wall of the tyre. This is because in practice the tyre deforms the most during the adiabatic transition. If this method uses a temperature sensor, the relative variation of the measured temperature is greater compared to the absolute temperature measured because the thermal inertia of the tyre casing is lower, while the wheel, in particular made of metal, has intrinsically a greater inertia than the tyre. As a result, the accuracy of the temperature measurement is improved, thus improving the quality of the method of measuring the variation of the load.

[0008] With the variation of the inflation pressure of the fluid chamber, the variation of the internal temperature of the fluid in the fluid chamber can be determined, for which purpose the variation of the internal temperature is defined by an evolution law determined previously in the preliminary phase. Thus, this evolution law converts the measured value of the internal pressure of the fluid in the fluid chamber into an evaluated value of the internal fluid temperature produced only by the adiabatic transition.

[0009] Then, the first intermediate variation of the volume can be evaluated with a model of the fluid that has undergone the adiabatic transition. Here the term "adiabatic" means that the transition undergone by the fluid, due to the connection of the trailer to the vehicle, occurs without external heat exchange between the fluid chamber and the outside of the tyre wheel assembly, which assumes that this transition is fast. As a result, by using only the variation of the measured inflation pressure and the variation of the internal temperature determined from the variation of the pressure in the fluid chamber according to the evolution law, the first variation of the volume of the fluid chamber caused by the connection of the trailer to the vehicle can be estimated, the fluid having undergone the adiabatic transition. For air or nitrogen, it can be entirely reasonable to assume that the gaseous fluid inside the fluid chamber of the tyre wheel assembly equipped with the pressure sensor is an ideal gas.

[0010] Preferably, a second intermediate variation of the volume is evaluated using a second transition of the fluid. This second transition is related to the thermal equilibrium of the fluid between the constituent parts of the tire wheel assembly, mainly the tire casing, and the outside. Thus, during the transient process related to the connection of the trailer but after the first transition of the fluid, i.e. when the inflation pressure changes its temporal evolution, the recorded variation of the internal temperature in the fluid chamber is used to evaluate the second variation of the volume undergone by the tire wheel assembly in this second transition. Taking into account the second variation of the volume ensures a higher accuracy in the evaluation of the variation of the volume of the fluid chamber, thus improving the measurement accuracy of the variation of the load of each tire wheel assembly equipped with a pressure sensor. However, the first intermediate variation of the volume is sufficient to estimate the overload applied to the tire wheel assembly on a first order.

[0011] Of course, taking into account the variation of the external temperature of the tire wheel assembly due to the thermal equilibrium of the tire wheel assembly also makes it possible to improve the measurement of the second variation of the volume at each tire wheel assembly equipped with a pressure sensor, resulting from the connection of the trailer to the vehicle. However, in a simple method, the initial internal temperature T1 of the fluid in the fluid chamber of the tire wheel assembly can be taken as the external temperature, since the tire wheel assembly is preferably in a thermo-mechanical steady state.

[0012] These two transitions can occur in each time increment, or one after the other in a measurement over a period of time. These evaluations of the intermediate variations of the volume require the use of measured values established from the establishment of a mechanical and possibly thermal equilibrium of the tire wheel assemblies of the trailer during the transient period of loading of the trailer. Once these forms of equilibrium are established, the variations of the temperature and pressure of the fluid chamber tend towards zero, thus reaching a further thermo-mechanical steady state.

[0013] Once the intermediate variation of volume of each tyre wheel assembly equipped with a pressure sensor has been evaluated, it is necessary to evaluate the associated variation of static load due to the connection of the trailer for each tyre wheel assembly equipped with a pressure sensor of the trailer. To do this, the intermediate variation of volume of each tyre wheel assembly needs to be converted into a variation of equivalent load. To do this, it is necessary to take into account a characteristic of the tyre wheel assembly, in particular of the tyre, called flatness stiffness per unit of volume KP. This quantity provides a link between the load supported by the tyre wheel assembly and the variation of volume of the fluid cavity resulting from the supported load, at the moment when the tyre wheel assembly is flattened on the ground perpendicular to the applied load. This characteristic can of course be a default quantity, or obtained by experimental characterization of the tyre wheel assembly, or deduced by numerical simulation activities on the same tyre wheel assembly. The tyre wheel assembly needs to be in working conditions close to those observed during the preliminary phase (i.e. around the internal temperature T1 and the inflation pressure P1). Generally, this flatness stiffness of the tyre wheel assembly is a quantity defined locally in the reference system relating to the internal pressure P, the internal temperature T and the volume V of the fluid cavity, around the initial working point of the tyre wheel assembly.

[0014] Preferably, before the main step, at least one tyre wheel assembly equipped with a pressure sensor is in a thermomechanical steady state.

[0015] Preferably, the transient phenomena recorded by the sensors of the electronic device are due only to the disturbance of the trailer balance resulting from the connection of the trailer to the towing vehicle. Thus, other disturbances do not affect the response of the sensors, which improves the accuracy of the load variation evaluated using this method. However, the method remains fully relevant if the disturbance of the trailer balance occurs on a different timescale from the disturbances associated with the connection of the trailer, or if this disturbance is manifested in the response of the sensors of the electronic device in the form of a small amplitude. The method remains fully relevant.

[0016] Advantageously, the pressure sensors and / or the temperature sensors are located in a sub-space of the closed fluid cavity defined by the tyre casing and the wheel.

[0017] Advantageously, the sensors measuring the low-amplitude transient phenomena are located close to where these transient phenomena occur, so that these sensors are not overwhelmed by measurement noise. Thus, for example, when there is a centralized tyre pressure monitoring system for the tyre wheel assemblies, it is advantageous for the sensors to be located on the tyre wheel assemblies and not in the centralized system. On the same logic, if the sensors are located on the tyre surface on the inside of the tyre, the measurements will be more accurate than if the sensors are mounted on the rim, since the latter measurement point is further away from where the physical phenomena occur that act on the deformation of the tyre casing due to the transient nature of the physical phenomena. Finally, preferably, the sensors, in particular the temperature sensors, are located away from the wheel, the thermal inertia of which is higher than that of the tyre.

[0018] Advantageously, the pressure sensor works with a resolution of less than 1 mbar.

[0019] Thus, smaller volume variations, and therefore smaller load variations, can be evaluated.

[0020] Preferably, the acquisition frequency F1 is between 0.1 Hz and 10 Hz.

[0021] Optionally, the acquisition frequency F2 is lower than the acquisition frequency F1.

[0022] In order to capture the rapid first transitions of the fluid, it is advantageous to set the acquisition frequency F1 to be high. Since the frequency F2 is linked to the recording of the second sensor, it is not necessary to have such a high frequency, since the second transitions of the fluid are intrinsically slower. However, it is entirely possible to use the same acquisition frequency for both sensors, in which case the frequency F1 is used as a reference.

[0023] According to one particular embodiment, the determination of the initial volume V0 takes into account the geometry of the rim and the geometry of the unloaded tire mounted on the rim and inflated to a reference pressure P0, preferably P0 is the initial pressure P1.

[0024] Advantageously, the geometry of the tire and / or the geometry of the rim are determined using an identifier of the tire and / or of the wheel of the tire wheel assembly equipped with a pressure sensor, preferably said identifier of the tire and / or of the wheel is obtained by radio frequency interrogation of an electronic device located on the tire wheel assembly.

[0025] In order to initialize the measurement system, in particular to determine the initial volume V1 of the fluid chamber, it is necessary to determine the volume V0 of the fluid chamber corresponding to the volume defined by the unloaded tire wheel assembly, i.e. the tire casing is mounted on the rim with a reference inflation pressure P0, preferably this reference inflation pressure P0 is the initial pressure P1.

[0026] To determine this volume V0, it is necessary to know the axisymmetric geometry of the unloaded tire at the reference inflation pressure P0. Indeed, it is assumed that the geometry of the rim is not affected by the inflation pressure of the tire wheel assembly. These geometries can be obtained through a tire database. Knowing the identity information of the tire and / or of the rim, the correct geometry can be precisely determined in this database. The identity information of the tire can be obtained by optically reading a regulatory marking affixed to the tire sidewall. The identity information can also be transmitted by radio frequency interrogation of an electronic device present on the tire wheel assembly, such as a Radio Frequency Identification (RFID) tag, a Tyre Mounted Sensor (TMS) installed on the inner liner of the tire or a Tyre Pressure Monitoring System (TPMS) installed on the rim.

[0027] Preferably, the load Z on each tire wheel assembly equipped with a pressure sensor is estimated using a first relationship of the following formula: [Formula 1] where K PP is the aerodynamic flattening rigidity per unit volume of the tire of the tire wheel assembly.

[0028] This is a simple and basic model that links the load applied to the tire to the change in volume of the fluid cavity of the tire wheel assembly between a first volume state V0 (for example, unloaded) and a second volume state V1, to the inflation pressure P of the fluid cavity and to the aerodynamic rigidity of the flattened tire wheel assembly corresponding to the overall level of the tire wheel assembly on the contact plane (in other words, regardless of the pressure P, the volume V and the temperature T). With this model, it is assumed that the structural rigidity of the tire wheel assembly is negligible compared to the aerodynamic rigidity, which is realistic for the tires of a trailer. However, in the previous formula, the structural rigidity of the tire is fully taken into account by adding the product of the structural rigidity and the aerodynamic rigidity of the tire multiplied by the inflation pressure.

[0029] According to an advantageous embodiment, the change in volume AV of each tire wheel assembly equipped with a pressure sensor is estimated by solving the following differential equation: [Formula 2] , [Formula 3] , where P is the internal pressure of the fluid cavity, V is the internal volume of the fluid cavity and T is the internal temperature of the fluid cavity.

[0030] This differential equation shows the link between the parameters of the fluid in the tyre wheel assembly cavity, which are first determined by the adiabatic transformation of the fluid and secondly by the fact that the fluid is an ideal gas.

[0031] The application also relates to a method for estimating the load supported by a trailer rigidly connected to a vehicle, comprising a method for estimating the variation in the load supported by the tyre wheel assemblies of the trailer resulting from the connection of the trailer to a stationary vehicle, the method being characterised in that, in a preliminary phase, it comprises a step of determining a first load distribution on the various axles of the trailer, preferably on the various tyre wheel assemblies of the trailer, associated with the application of an additional load to the coupling point M of the trailer to the vehicle, the method optionally also comprising a step of determining a second load distribution on the various axles of the trailer, preferably on the various tyre wheel assemblies of the trailer, associated with the weight of the trailer, in a main phase, it comprises a step of estimating the load Z supported by the various tyre wheel assemblies of the various axles i of the trailer using the variation ΔZ in the load supported by at least one tyre wheel assembly equipped with a pressure sensor, the first load distribution associated with the application of an additional load at the coupling point M and the initial load Z1i of the various tyre wheel assemblies of the trailer, and optionally the second load distribution associated with the weight of the trailer, and it comprises a step of comparing the estimated load Z supported by the various axles i of the trailer and / or the total load supported by the trailer, which is the sum of the loads supported by the various axles i of the trailer, with at least one threshold value S, when said at least one threshold value S is exceeded, in a secondary phase, the mass content K of the trailer is modified in the trailer, after which all the steps of the main phase are performed again.

[0032] By adding the loads supported by the tyre wheel assemblies or axles before the connection of the trailer, it is possible to evaluate the total load of the tyre wheel assemblies or axles i of the trailer. Evaluating the total load supported by the trailer then amounts to simply summing the static loads established on all the axles i of the trailer. It is then possible to verify, even before the trailer begins to move, whether the load state of the various tyre wheel assemblies, of the various axles, and of course of the trailer itself, complies with the road traffic safety regulations.

[0033] By knowing the first load distribution of the tire wheel assemblies or axles i of the trailer in relation to the overload applied to the hitch point M of the connection of the trailer, it is possible to deduce from the individual measured values on the tire wheel assemblies equipped with measuring devices the overload on each tire wheel assembly or each axle of the trailer in relation to the connection of the trailer to the vehicle. By summing the overload in relation to the connection of the trailer and the static load experienced by each tire wheel assembly in relation to the mass of the trailer, it is possible to estimate the total load applied to each tire wheel assembly or each axle i of the trailer. Alternatively, the static load in relation to the mass of the trailer is obtained by the second load distribution on the tire wheel assemblies or axles i of the trailer in relation to the mass of the trailer.

[0034] If the connected trailer does not meet the safe driving conditions, it is necessary to change the layout of the trailer contents, either on individual tire wheel assemblies, axles or the entire trailer, even if this means disconnecting the trailer from the vehicle to move the center of gravity of the trailer. This movement of the center of gravity of the trailer is able to differently distribute the mass of the trailer carried by each axle of the trailer or by the towing seat of the towing vehicle. Once the new layout has been achieved, it is necessary to re-run the method from the main phase by connecting the trailer in the new layout and analyzing the load experienced by each tire wheel assembly of the trailer equipped with pressure sensors. For example, this new layout of the trailer can be a movement of the center of gravity of the trailer contents or a lightening of the trailer contents, or a combination of both.

[0035] The invention also relates to a system implementing a method for estimating the variation of the load experienced by the tire wheel assemblies of a trailer firmly connected to a vehicle resulting from the connection of the trailer to a stationary vehicle and / or a system implementing a method for estimating the load experienced by a trailer firmly connected to a vehicle, the system comprising: • a trailer on which a hitch device is installed at point M, which device is able to accommodate a towing seat of a vehicle, each axle i of the trailer comprising at least one tire wheel assembly equipped with electronic devices; • the electronic devices comprising at least one pressure sensor, at least one electronic chip, at least one storage space able to record signals from the sensor, and at least one first radio frequency communication device able to at least emit, the electronic devices being preferably fixed to the internal wall of the tire, very preferably in the crown of the tire; • at least one computing device; and • at least one display device comprising at least one second radio frequency communication device able to at least receive.

[0036] As described in the method, the pressure sensor should be located on the tire wheel assembly that performs a rotational movement relative to the trailer. In order to be far from the elements of the tire wheel assembly that have the greatest thermal inertia, the electronics are fixed to the inner wall of the tire, at the tire crown, in particular if the device comprises a temperature sensor. Thus, the electronics that at least regulate the signal from the pressure sensor should be provided with a communication device that can emit, for example a radio frequency communication device, in order to simply transmit the data outside the tire wheel assembly, at least where the display device is located. In particular, one alternative is to integrate into the tire wheel assembly a calculation device that calculates the variation of the volume of the tire wheel assembly's inner cavity. This calculation device can be integrated into the electronics or be in wired communication with the electronics. The radio frequency communication device of the electronics then facilitates the transmission of the calculation result outside the tire wheel assembly. The radio frequency communication from the electronics of the tire wheel assembly can be intended for the trailer, the vehicle or somewhere outside these two components and for a device separate from these components, such as a smartphone, a tablet, a computer. These three elements can represent the display device. However, the display device can also be a graphic interface of the trailer, the vehicle, such as on the dashboard.

[0037] Thus, the proposed structural form can be adapted to a plurality of possible technical configurations, while having the function of implementing the described method.

[0038] Preferably, the system comprises an analysis device that can analyze the result output by the at least one calculation device.

[0039] The result of the calculation device is the variation of the load supported by each tire wheel assembly equipped with electronics and / or the load supported. If this second quantity is to be compared with a threshold S, an operation needs to be performed before sending the message to the display device. An optional element of the system that can serve the user of a semi-trailer truck unit composed of a tractor and a trailer needs to be located between the calculation device and the display device. Structurally, it can be associated with one and / or the other by a wired connection, or it can be physically separate from these elements by a radio frequency communication device.

[0040] According to a first particular embodiment, the at least one calculation device comprises at least one third radio frequency communication device that can emit / receive.

[0041] In the case where the calculation device is physically separate from the electronics and the display device, it needs to be able to communicate with the other two elements. For example, when the calculation device is on the vehicle, it is in this case that it collects the pressure data from the electronics by radio frequency communication with the electronics. On the other hand, if the display device is on a smartphone, it sends the calculation result to the display device by this radio frequency communication.

[0042] According to a second particular embodiment, the at least one analysis device comprises at least one fourth radiofrequency communication device capable of emitting / receiving.

[0043] In the case where the analysis device is physically separated from the computing device and the display device, it needs to be able to communicate with the other two elements. This is the case, for example, when the analysis device is located on a server remote from the vehicle: it collects the variations in load or the load applied to the various tire wheel assemblies of the vehicle from the computing device by radiofrequency communication with the computing device present on the vehicle. On the other hand, if the display device is on a cell phone or any other electronic device equipped with a screen, the analysis device sends the message resulting from the comparison to the display device by radiofrequency communication.

[0044] According to a third particular embodiment, the system comprises at least one reading device capable of at least reading the data contained in the at least one memory space of the electronic device, the at least one reading device comprising at least a fifth radiofrequency communication device capable of emitting / receiving.

[0045] In the case where the communication range of the electronic device is not sufficient to ensure communication for the display device, a reading device should be used to collect the data from the electronic device. This reading device performs the function of capturing the measurement data. Then, the reading device transmits these data by radiofrequency communication to the display device or to any other element of the system that needs the data, in preparation for the rest of the method. The reading device acts as an information relay, thus optimizing the communication coverage with respect to the electronic device present in the tire wheel assembly. In particular, in order to reduce the mass of the electronic device at the tire, the source of energy needed for the data transmission, which is an energy-consuming function of the electronic device, should be limited.

[0046] Preferably, a part of the communications between the elements contained in the group comprising the electronic device, the at least one computing device, the at least one display device, the at least one analysis device and the at least one reading device is performed by the communication devices using UHF radio waves, preferably using Bluetooth Low Emission (BLE).

[0047] The Ultra-High Frequency (UHF) band makes it possible to carry out a large amount of data transmission at an advantageous bit rate, in particular at the higher frequencies of the UHF band, such as the BLE band. The UHF band is generally used for traffic applications, which means that the communication devices of the system can share the resources of the communication devices already present in the vehicle or in the roadside infrastructure.

[0048] Advantageously, the at least one display device is contained in the group comprising a telephone, a computer, a human-machine interface located on the trailer and / or on the vehicle, preferably on the dashboard of the vehicle.

[0049] The display device serves to warn a person operating the semitrailer truck unit, whether this person is the driver sitting on the driver's seat or another person in charge of the semitrailer truck unit compliance, about the safety status of the trailer of the semitrailer truck unit.

[0050] According to an advantageous embodiment, a part of the at least one reading device is located on the trailer.

[0051] According to another advantageous embodiment, a part of the at least one computing device and / or a part of the at least one analyzing device is located on the trailer, preferably on the tire wheel assembly.

[0052] The trailer plays the role of a natural information relay, since the tire wheel assembly is connected to the trailer and the safety conditions apply to the trailer. Thus, although it is highly desirable that the structural devices of the system are located on the trailer, alternatives are possible. However, the trailer offers a certain degree of data confidentiality, unlike the communication with for example a server, unless a secure communication protocol is set. Of course, in order to minimize the impact of the system on the trailer environment, which is nowadays complex and heavily loaded, positioning the functions on the tire wheel assembly makes it possible to limit the disturbances with other structural components of the trailer and / or of the vehicle. BRIEF DESCRIPTION OF DRAWINGS

[0053] The application will be better understood by reading the following description, given only by way of non-limiting example and with reference to the appended drawings, in which the same reference designates always the same elements, in which: Figure 1 a method and / or a system implementing a method for estimating the variations of the load supported by a tire wheel assembly of a trailer firmly connected to a towing vehicle according to a first embodiment of the application are illustrated; Figure 2 another configuration of a system according to a second embodiment of the application is illustrated; Figure 3 a block diagram of a method for estimating the variations of the load supported by a tire wheel assembly of a trailer firmly connected to a vehicle and / or of the load supported according to the application is illustrated; Figure 4 a time evolution of the internal pressure of the fluid cavity of the pressure sensor output is illustrated; Figure 5 a time evolution of the internal temperature of the fluid cavity is illustrated; Figure 6 an estimation of the variations of the volume of the fluid cavity with respect to time according to the application is illustrated; Figure 7An estimation of the variation of the load of the tire wheel assembly of a trailer in relation to time in connection with the connection of the trailer to a vehicle is shown. DETAILED DESCRIPTION

[0054] Figure 1 An example of a system 2000 implementing a method for estimating the variation of the load of the tire wheel assemblies of a trailer firmly connected to a towing vehicle and / or a method for estimating the load of the tire wheel assemblies of a trailer firmly connected to a towing vehicle is shown. The system 2000 comprises a trailer 2001 comprising three axles of tire wheel assemblies 2006 distributed on the trailer 2001. The trailer 2001 comprises a point M located at the front of the trailer, the hitch point (not shown in the figure) for connecting the towing vehicle. However, the towing vehicle exerts an external force ΔZ on the trailer 2001 at the point M. The trailer 2001 has a center of gravity G to which the weight P of the trailer is applied, which corresponds to the force resulting from the total mass of the trailer taking into account the force of gravity of the Earth. This weight P is balanced by the reaction forces applied on the tire wheel assemblies 2006 of the trailer, which are called Z1 to Z3 depending on the axle of the tire wheel assembly 2006 to which they are connected. The external force ΔZ at the point M of the vehicle, which corresponds to the connection of the connection means of the trailer 2001 to the vehicle, causes additional reaction forces denoted respectively ΔZ1 to ΔZ3 to be applied to the tire wheel assemblies 2006 of each respective axle, which stabilize when a steady state is reached, to balance the external force ΔZ. The additional reaction forces ΔZ1 to ΔZ3 take into account the reaction of the ground on the outrigger devices of the trailer 2001.

[0055] The aim of the method is to determine the reaction forces on each tire wheel assembly of the trailer that will stabilize when a steady state is reached.

[0056] In this case, at least one tire wheel assembly 2006 of each axle of the vehicle 2001 is equipped with an electronic device 2007. The electronic device 2007 is located in the fluid chamber of the tire wheel assembly 2006. In this case, the electronic device 2007 is located on the inner wall of the tire, in line with the tread of the tire casing that provides the contact between the tire casing and the ground. It is possible to install the electronic device in the rim of the tire wheel assembly, while remaining inside the fluid chamber of the tire wheel assembly 2006. For example, the electronic device can be integrated into the rim valve, like certain Tyre Pressure Monitoring Systems (TPMS).

[0057] The electronic device 2007 comprises a pressure sensor associated with a microcontroller and at least a radiofrequency device capable of emitting. Thus, the radiofrequency device comprises a radio wave generator and a radio communication antenna for emitting the generated radio waves. The radiofrequency device can also optionally comprise a radio wave receiver for receiving instructions from the outside, for example to start taking measurements. The electronic device 2007 also comprises a storage space for storing the measurement data of the pressure sensor before transmitting them in the form of radio waves. The electronic device can transmit the raw measurement data or the data filtered by the microcontroller. Of course, the pressure sensor is usually accompanied by a temperature sensor. At this point, the electronic device 2007 transmits both the pressure and temperature data to the outside of the tire wheel assembly 2006. In this case, the electronic device 2007 emits radio waves in the Ultra High Frequency (UHF) band, more particularly in the Bluetooth Low Emission (BLE) band.

[0058] In this case, the outside of the tire wheel assembly 2006 comprises at least the trailer 2001. This trailer 2001 first comprises a radio data reader 2005 operating in the UHF band, the antenna 2105 of which is located in the vicinity of the tire wheel assembly 2006 during its rotation, to collect the measurement data generated by the electronic device 2007. The data are then transmitted here by wired means to a computing device 2002 located in the trailer 2001. Radiofrequency transmission can also be used with specific communication devices. The computing device 2002 comprises a storage space and a processor for performing the following tasks thereof: identifying the quantity of tire wheel assemblies corresponding to the initial state, solving the differential equation to determine the change in volume of the fluid chamber of each tire wheel assembly equipped with an electronic device 2007, and finally, after having previously collected the quantities of tires necessary for this last task, calculating the change in load related to the change in volume.

[0059] The results, in particular the last data, are sent to an analysis device 2004. Here, the data are transmitted by wired means, but radiofrequency communication can also be established. The analysis device 2004 compares the results of the computing device 2002 with the threshold values previously entered. These threshold values, such as the maximum allowed load per axle of the trailer or the total maximum load of the trailer or the maximum allowed load per tire wheel assembly, can be transmitted by entering these data in hard-coded form within the trailer 2001 or by consulting a database located outside the trailer 2001. Of course, the analysis device 2004 can be integrated into the computing device 2002.

[0060] Finally, the various output data from the analysis device 2004 are transmitted to the display device 2003 via a fourth communication device 2104 (concretely, implemented by a radio communication antenna of the trailer 2001) and the second communication device 2102 present on the display device 2003.

[0061] These communication devices 2104 and 2102 transmit the data to the tablet or smartphone 2003 through a communication network in order to inform whether the load of the trailer complies with the threshold value allowed to the trailer 2001 according to the current regulations.

[0062] In the case where the load of the trailer does not comply with the requirements, the trailer needs to be disconnected from the vehicle in order that the load can be changed (either by reducing the mass of the load or by changing the position of the load in the trailer) so that the load of the axles of the trailer 2001 is reduced when the trailer is connected to the towing vehicle. Then, the main phases of the method for estimating the load supported by the tire wheel assemblies of the trailer firmly connected to the vehicle are repeated in order to verify whether the load of the trailer complies with the current regulations. Although it is preferred to disconnect the trailer in order to change the load of the trailer, the operation of disconnection is still optional. It is entirely possible to continue recording the measurement signals of the electronic device 2007 while the load of the trailer is changed and then wait for the connected trailer 2001 to reach the overall equilibrium before estimating the load supported by each tire wheel assembly 2006 of the trailer 2001 equipped with the electronic device 2007. These new loads are then compared with the threshold value used previously in order to verify whether the trailer 2001 complies with the current regulations.

[0063] Figure 2 Another configuration of the system 2000 is illustrated. This system 2000 comprises a trailer 2001 comprising three axles of tire wheel assemblies 2006 distributed on the trailer, numbered 1 to 3 in the direction of travel of the trailer 2001. The trailer comprises a point M located at the front of the trailer, the hitch (not shown in the figure) for connecting a towing vehicle. However, this towing vehicle exerts an external force AZ on the trailer 2001 at the point M.

[0064] At least one tire wheel assembly 2006 of each axle of the trailer 2001 is equipped with an electronic device 2007. This electronic device 2007 is located in the fluid cavity of the tire wheel assembly 2006. In this case, the electronic device 2007 is located on the inner wall of the tire, aligned with the pattern of the tire casing providing the contact between the tire casing and the ground. The electronic device can be installed in the rim of the tire wheel assembly while remaining inside the fluid cavity of the tire wheel assembly 2006. For example, the electronic device can be integrated into the rim valve as certain Tyre Pressure Monitoring Systems (TPMS).

[0065] The electronic device 2007 comprises a pressure sensor associated with a microcontroller and at least a radiofrequency device capable of emitting. Thus, the radiofrequency device comprises a radio wave generator and a radio communication antenna for emitting the generated radio waves. The radiofrequency device can also optionally comprise a radio wave receiver for receiving instructions from the outside, for example to start the measurements. The electronic device 2007 also comprises a storage space for storing the measurement data of the pressure sensor before emitting them in the form of radio waves. The electronic device can emit the raw measurement data or the data filtered by the microcontroller. Of course, the pressure sensor is usually accompanied by a temperature sensor. At this time, the electronic device 2007 emits both the pressure and temperature data to the outside of the tire wheel assembly 2006. Here, the electronic device 2007 emits radio waves in the Ultra High Frequency (UHF) band, more particularly in the Bluetooth Low Emission (BLE) band.

[0066] In this case, the outside of the tire wheel assembly 2006 comprises at least the tractor and the trailer 2001. The trailer 2001 first comprises a radio data reader 2005 working in the UHF band, the reception antenna 2105 of which is located in the vicinity of the tire wheel assembly 2006 during its rotation, to collect the measurement data generated by the electronic device 2007. Then, the data, after processing, are transmitted here by wired means to the emission antenna of the communication device 2104 located in the trailer 2001. Radiofrequency transmission can also be used with specific communication devices. The computing device 2002 comprises a storage space and a processor for performing its following tasks: identifying the quantity of tire wheel assemblies corresponding to the initial state, solving the differential equation to determine the change in volume of the fluid cavity of each tire wheel assembly equipped with an electronic device 2007, and finally, after having previously collected the quantity of tires necessary for this last task, calculating the change in load related to the change in volume.

[0067] Then, the data are transmitted here by wired means to the computing device 2002 located in the trailer 2001. However, the data can also be transmitted to physical devices located outside the trailer 2001.

[0068] The first device is the computing device 2002, which comprises communication devices capable of emitting / receiving. These communication devices are in Figure 2In the configuration shown in figure 1, the receiving communication means 2105 are integrated into the computing means 2002. In other configurations, it is possible to receive the radio waves emitted by the transmitting communication means 2105 in order to convert them into digital data usable by the computing means 2002. This computing means 2002 comprises a storage space and a processor for performing its following tasks: identifying the quantity of tyre wheel assemblies corresponding to the initial state, solving the differential equation in order to determine the variation of the volume of the fluid cavity of each tyre wheel assembly equipped with the electronic device 2007, and finally, after having previously collected the tyre quantities necessary for this last task, calculating the variation of the load related to the variation of the volume.

[0069] The results, and in particular the final data, are sent to a second device corresponding to the analysis device 2004. Here, these data are transmitted by wired communication. The analysis device 2004 compares the results of the computing means 2002 that it collects (this communication can be a radio frequency transmission made from the computing means 2002 with the receiving communication means 2104) with the thresholds previously entered. These thresholds, such as the maximum allowed load per axle of the vehicle or the total maximum load of the vehicle or the maximum allowed load per tyre wheel assembly, can be transmitted by querying a remote database containing data related to the trailer 2001. Of course, the analysis device 2004 here is integrated into the computing means 2002.

[0070] Finally, the various output data from this analysis device 2004 are transmitted to the display device 2003 via the transmitting fourth communication means 2104 and the second communication means 2102 present on the display device 2003. Here, the display device consists of a digital tablet 2003 possibly remote from the trailer 2001 and a human-machine interface possibly included in the trailer 2001 comprising a display screen. These display devices can also be a screen on the dashboard of the towing vehicle, with radio frequency transmission of the data to be displayed.

[0071] The purpose of the display device 2003 is to inform whether the load of the trailer complies with the thresholds allowed according to the current regulations.

[0072] Of course, these two embodiments of the system for estimating the variation of the load and / or the load supported by the tyre wheel assemblies of a vehicle firmly connected to a trailer are only illustrative examples of this system and are not limited to these two configurations. The first extreme configuration is to integrate all the computing and analysis devices into the electronic device on board the tyre wheel assemblies, which transmits the results to a display device remote from the trailer. The other extreme configuration is to transmit the measurement data recorded on the electronic device by radio waves and to perform the other steps of the method on a device remote from the vehicle, without involving the trailer or the towing vehicle.

[0073] Figure 3A method and / or block diagram of a method for estimating changes in load experienced by a tire wheel assembly of a trailer that is rigidly connected to a stationary towing vehicle is shown. The method includes a plurality of stages.

[0074] The first phase is a preparatory phase, comprising at least the actions 1 to 6 followed one another by the connection system depicted by the solid lines. This preparatory phase, which focuses on the unconnected trailer, obviously comprises the equipment of the trailer and thus the loading of the trailer by the installation of a pressure sensor at the tire wheel assembly, ideally, which is able to measure the pressure of the fluid cavity defined by the inner surface of the tire and the rim by dedicated electronic means. The first steps, labeled 1 and 2, comprise the determination of physical quantities related to the fluid cavity of the tire wheel assembly equipped with the measuring means, such as the inflation pressure Pi and the internal temperature Ti. Preferentially, these determinations can be made with default values or by capturing specific measured values. The step labeled 3 comprises the determination of the load Zi supported by the tire wheel assembly equipped with the measuring means in the unconnected state. This determination can be made with default values by assuming the distribution of the total load of the trailer between its various axles; the total load of the trailer is a data given for example by the trailer manufacturer and corresponds for example to the unloaded mass of the trailer as specified in the technical specifications of the trailer manufacturer. Of course, this determination can also incorporate the loading of the trailer. The step labeled 4 corresponds to the acquisition of specific quantities of the tire wheel assembly equipped with the measuring means. One of these quantities is the volume Vo which corresponds to the volume occupied by the fluid cavity of the tire wheel assembly inflated to the pressure Pi (strictly speaking at the internal temperature Ti) but completely unloaded (i.e. even not resting on the ground). The second quantity is the flattening stiffness Kp per unit volume of the tire casing of the tire wheel assembly, which can depend on the inflation pressure Pi, the internal temperature Ti and the load Zi supported. Finally, the third set of quantities is related to the ideal gas behavior law for the properties of the gas contained in the fluid cavity of the tire wheel assembly. Furthermore, the penultimate step of the preparatory phase, labeled 5, is the determination of the volume Vi occupied by the fluid cavity of the instrumented tire wheel assembly under the inflation pressure Pi and the temperature Ti, under the load Zi. Finally, the last step of the preparatory phase, labeled 6, is the evaluation of the amount of gas contained in the fluid cavity of the instrumented tire wheel assembly by determining the number of moles n of gas present within the volume Vi. Here, although the hypothesis related to the ideal gas state is indeed applicable, it is still necessary to identify the properties of the gas composition, i.e. whether the gas is a single-species gas or a gas mixture. Furthermore, in this preparatory phase, even if not shown, it is essential to determine the evolution law that links the variation of the internal pressure P of the fluid in the fluid cavity of the relevant tire wheel assembly to the variation of the internal temperature T in the course of the adiabatic transition in the vicinity of the operating point (i.e. the pressure Pi, the temperature Ti and the load Zi) of the tire wheel assembly. Finally, in the preparatory phase, even if not shown, it is necessary to determine the load distribution on the various axles of the trailer, preferably on the various tire wheel assemblies of the trailer, which is related to the load applied at the connection point M of the trailer.Optionally, a second load distribution on the respective axles of the trailer, preferably on the respective tire wheel assemblies of the trailer, can be envisaged in the unconnected state of the trailer. This second load distribution is related to the total mass of the trailer in the unconnected state.

[0075] The method proceeds next to the main phase, which begins with the connection of the trailer to the towing vehicle. The time variation of the inflation pressure P(t) of the instrumented tire wheel assemblies of the trailer must be recorded, which in the case of a trailer for light vehicles is of the order of 1 mbar. These recordings are then stored in a memory space so that, first of all, the raw data can be filtered using a low-pass filter to eliminate high-frequency phenomena, which corresponds to step 11. Next, the time variation of the internal temperature T(t) of the fluid chamber is determined using the time variation of the internal pressure P(t) using the evolution law determined in the preliminary phase, which corresponds to step 12. Optionally, if the instrumented tire wheel assemblies of the vehicle are equipped with temperature sensors, the time variation of their internal temperature T(t) is recorded, which also corresponds to step 12. In this option, the recorded variation of the internal temperature T(t) is used to assess the isobaric or monobaric transition of the fluid of the fluid chamber corresponding to the establishment of a thermal equilibrium between the fluid chamber and the external environment, which is necessary for the adiabatic transition of the fluid associated with the connection of the trailer. The connection system between the optional steps and the indispensable steps of the method is represented by a line in grey instead of black. However, the connection lines belonging to the main phase are shown in dotted lines, while the connection lines of the preliminary phase are shown in solid lines. Finally, as will be seen later, the secondary phase has a connection system depicted in broken lines (dotted lines).

[0076] One of the important steps of the main phase is the determination of the variation ΔV of the volume of the fluid chamber of the instrumented tire wheel assemblies by step 13. This corresponds to taking into account at least the adiabatic transition of the fluid of the fluid chamber due to the instantaneous hitching of the trailer to the towing vehicle, which modifies the thermo-mechanical equilibrium of all the tire wheel assemblies of the trailer, thus modifying the thermo-mechanical equilibrium of the fluid trapped in the respective fluid chambers of the tire wheel assemblies. Furthermore, it is assumed that the fluid behaves as an ideal gas. From the variation of the internal pressure P(t) of the instrumented tire wheel assemblies, the variation of the internal temperature T(t) can be determined using the evolution law determined in the preliminary phase for the adiabatic transition of the fluid.

[0077] The changes in internal pressure and internal temperature can be introduced into the differential equation taking into account the above assumptions. Solving this differential equation in time increments gives an estimate of the time variation of the volume of the fluid chamber ΔV(t) which corresponds to step 13. Optionally, the method can be complemented by measuring the internal temperature T of the fluid chamber to evaluate a second variation of the volume of the fluid chamber related to an isobaric or monobaric transition of the fluid due to the heat exchange between the fluid chamber of the tire wheel assembly and the external environment through the constituent parts of the tire wheel assembly, i.e. the tire casing and the wheel. This second transition is generally subsequent to the adiabatic transition since the temperature variation resulting from the adiabatic transition is the root cause of the lack of thermal equilibrium between the fluid chamber and the external environment.

[0078] Another important step of the main phase is the evaluation of the variation of the load supported ΔZ related only to the previously evaluated variation of the volume ΔV, which corresponds to step 14. To this end, it is necessary to take into account again the flattening stiffness K of the tire wheel assembly per unit of volume P . This stiffness can include an aerodynamic component and a structural component. Considering only the aerodynamic component K PP may be sufficient to provide a reliable estimate of the variation of the load supported ΔZ.

[0079] Based on the variation of the load supported ΔZ, it is necessary to add the initial load supported Z1 to obtain in step 15 the load supported by the instrumented tire wheel assembly. From this value on the scale of the tire wheel assembly, it is easy to back-calculate the load supported by each axle i of the trailer and thus the total load supported by the trailer. To this end, in the case where only one or several (but not all) of the tire wheel assemblies of the trailer are equipped with measuring devices, the method comprises, in a preliminary phase, estimating the load distribution on each tire wheel assembly or each axle of the trailer, which is related to the overload applied at the hitch point M of the trailer. Optionally, a second load distribution can be used to estimate the initial load on each tire wheel assembly or each axle of the trailer, which is related only to the total mass of the trailer.

[0080] The last step, marked 16, is to compare the load supported Z by each tire wheel assembly with a threshold value S and in the same way for each axle i of the trailer, finally for the entire trailer. In general, these threshold values S can be safety conditions specific to the road fitness of the semi-trailer truck unit composed of the tractor and the trailer, according to the national regulations.

[0081] According to the result of this comparison, the semitrailer truck unit can go on the road with the trailer connected to the tractor, since according to step 17 of the main phase, all the safety conditions have been met. If this is not the case, the method loops to a secondary phase comprising at least step 20 in which the load of the connected trailer is changed. This change of load can occur while the trailer remains connected. It is also conceivable to cause the trailer to be unhooked from the vehicle while the change of load of the trailer is performed. The change of load comprises changing the position of the load in the trailer and / or modifying the content of the load, so as to for example reduce the mass of the load. Once step 20 is completed, it is necessary to restart the main steps, connecting the trailer again to the vehicle if necessary, and recording the inflation pressure and optionally the internal temperature of the instrumented tire wheel assemblies of the vehicle, which respectively correspond to steps 11 and 12 of the block diagram. This secondary phase is repeated until the criteria enabling step 17 to be performed are met.

[0082] Figure 4 The time evolution of the pressure delivered by the pressure sensor of the electronic device located on the tire wheel assembly of the trailer is shown. The curve consisting of points 10 is the raw measurement of the pressure sensor, while curve 11 corresponds to the time evolution of the pressure filtered, cleared of high-frequency noise. This second curve will then be used in the block diagram of Figure 3 .

[0083] This time-based recording of the internal pressure of the fluid cavity of the tire wheel assembly begins with a preliminary phase before the trailer is connected to the tractor. The moment of connection of the trailer corresponds to the abscissa value of the point 100 marking the beginning of the main phase. It can then be seen that from this point 100, the internal pressure of the fluid cavity rapidly decreases until the point 101 at which the decrease in pressure stops and the pressure even rises, to a lesser extent. This point 101 marks the transition between the fluid work related to the connection of the trailer and the heat exchange with the outside, the former corresponding to a first transformation of the fluid, which can be similar to an adiabatic transformation, and the latter corresponding to a second transformation of the fluid. Considering that the time origin is the abscissa value of the point 100, the abscissa value of this point 101 corresponds to a duration To. Thus, the preliminary phase 50 ends at the abscissa value of the point 100. This phase precedes the main phase, which is divided into two successive phases. The first phase 51 can be similar to an adiabatic transformation of the fluid, corresponding to the work done by the fluid after the connection of the trailer. The second phase 52 corresponds to the heat exchange between the fluid and the outside.

[0084] Figure 5The time evolution of the internal temperature of the fluid cavity is shown. Here, this time evolution is delivered by a temperature sensor of the electronic device located on the tire wheel assembly of the trailer, as shown by the curve 12. In the absence of a temperature sensor to make the measurement, an alternative is an estimation of the internal temperature, as shown by the curve 12', which is based on, on the one hand, the recorded internal pressure and on the evolution law linking the internal temperature to the internal pressure during the adiabatic transformation of the fluid, and, on the other hand, on the temperature outside the tire wheel assembly, which is the basis for the thermal exchanges between the fluid of the fluid cavity and the environment outside the tire wheel assembly by means of a thermal exchange coefficient. This thermal exchange coefficient takes into account the thermal characteristics of the tire wheel assembly. In this alternative, the curve 70 shows the evolution of the temperature outside the tire wheel assembly.

[0085] These evolutions 12 and 12' of the internal temperature of the fluid cavity of the tire wheel assembly begin with a preliminary phase before the connection of the trailer to the towing vehicle. The moment of connection of the trailer corresponds to the abscissa value of the point 100 marking the beginning of the main phase. It can then be seen that, from this point 100, the internal temperature of the fluid cavity decreases rapidly until the point 101, at which the decrease in temperature stops, then the temperature increases to a lesser extent. This point 101 marks the transition between the fluid work related to the connection of the trailer and the thermal exchanges with the outside, the former corresponding to a first transformation of the fluid, which can be similar to an adiabatic transformation, and the latter corresponding to a second transformation of the fluid. Considering that the time origin is the abscissa value of the point 100, the abscissa value of this point 101 corresponds to a duration To. Thus, the preliminary phase 50 ends at the abscissa value of the point 100. This phase precedes the main phase, which is divided into two successive phases. The first phase 51 can be similar to an adiabatic transformation of the fluid, corresponding to the work done by the fluid after the connection of the trailer. The second phase 52 corresponds to the thermal exchanges between the fluid and the outside.

[0086] Here, it can be seen that the difference between the recorded curve 12 and the estimated curve 12' of the internal temperature, on the one hand, illustrates the inertia specific to the temperature sensor. On the other hand, the hypothesis of the evolution law linking the internal pressure of the fluid to the internal temperature during the adiabatic transformation can also be overestimated. However, the trends between these curves 12 and 12' are very similar. Finally, in this case, the temperature outside the tire wheel assembly is not measured, but is determined by extrapolation of the internal temperature of the fluid cavity of the preliminary phase, which is also a source of potential error. This estimation corresponds to Figure 5the tire and the outside environment, and a heat exchange coefficient λ depending on the thermal properties of the tire material properties, and on the distribution of the different types of heat exchange of the tire outer casing, such as radiation, conduction and convection. This coefficient λ can be estimated by the evolution of the internal temperature of the fluid cavity in a preliminary phase, for example, before the main phase.

[0087] Figure 6 The time evolution of the internal volume of the fluid cavity is shown. In this case, this time evolution, represented by the curve, is the output of the calculation of the variation of the volume with the differential equation proposed, which also takes into account the thermal equilibrium with the outside environment.

[0088] This evolution 13 of the internal volume of the fluid cavity of the tire wheel assembly begins with a preliminary phase before the connection of the trailer to the tractor. The time of connection of the trailer corresponds to the abscissa value of the point 100 marking the beginning of the main phase. It can then be seen that, from this point 100, the internal temperature of the fluid cavity increases rapidly until the point 101, at which the increase in temperature stops, then the volume decreases to a certain extent. This point 101 marks the transition between the fluid work related to the connection of the trailer and the heat exchange with the outside, the former corresponding to a first transformation of the fluid, which can be similar to an adiabatic transformation, the latter corresponding to a second transformation of the fluid. Considering that the time origin is the abscissa value of the point 100, the abscissa value of this point 101 corresponds to a duration To. Thus, the preliminary phase 50 ends at the abscissa value of the point 100. This phase precedes the main phase, which is divided into two successive phases. The first phase 51 can be similar to an adiabatic transformation of the fluid, corresponding to the work done by the fluid after the connection of the trailer. The second phase 52 corresponds to the heat exchange between the fluid and the outside.

[0089] It is noted that, at the end of the phase 51, a good estimate of the variation of the volume of the tire wheel assembly has been obtained, which clearly shows that the work resulting from the change in load supported by the tire wheel assembly mainly occurs during the phase 51. The observed variations or oscillations correspond to fluctuations of the transient phase corresponding to the establishment of thermal equilibrium. Thus, the method described herein can produce a continuous measurement of the temporal variation of the load applied to the tire wheel assembly in the time domain.

[0090] Figure 7The time evolution of the variation of the load applied to the tire wheel assembly equipped with electronic devices is shown. In this case, this time evolution, represented by the curve 14, is the output of the calculation of the variation of the volume with the proposed differential equation multiplied by the flattening stiffness of the tire wheel assembly, which takes into account the thermal equilibrium with the external environment. In this case, the stiffness used is the local identified stiffness based on the initial pressure of the tire wheel assembly, the initial load applied to the tire wheel assembly and corresponding to the initial temperature. The global stiffness defined by the proposed formula can be adopted, which has given good orders of magnitude.

[0091] This evolution 14 of the internal volume of the fluid cavity of the tire wheel assembly begins in the preparatory phase before the connection of the trailer to the tractor. The moment of connection of the trailer corresponds to the abscissa value of the point 100 marking the beginning of the main phase. It can then be seen that, from this point 100, the internal temperature of the fluid cavity increases rapidly until the point 101 at which the increase in temperature stops and then decreases to a certain extent. This point 101 marks the transition between the fluid work related to the connection of the trailer and the heat exchange with the outside, the former corresponding to a first transformation of the fluid, which can be similar to an adiabatic transformation, and the latter corresponding to a second transformation of the fluid. The abscissa value of this point 101 corresponds to the duration To, considering that the origin of time is the abscissa value of the point 100. Thus, the preparatory phase 50 ends at the abscissa value of the point 100. This phase precedes the main phase, which is divided into two successive phases. The first phase 51 can be similar to an adiabatic transformation of the fluid, corresponding to the work done by the fluid after the connection of the trailer. The second phase 52 corresponds to the heat exchange between the fluid and the outside.

[0092] It is noted that, at the end of the phase 51, a good estimate of the variation of the load applied to the tire wheel assembly has been obtained, which clearly shows that the work resulting from the variation of the load mainly occurs during the phase 51. The observed variations or oscillations correspond to fluctuations of the transient phase corresponding to the establishment of the thermal equilibrium. Thus, the method described herein can produce a continuous measurement of the temporal variation of the load applied to the tire wheel assembly in the time domain. The curve 80 corresponds to the measured values of the ground weigher on the overload applied to the tire wheel assembly of the trailer. In summary, the proposed method captures well the variations of the applied load.

Claims

1. A method for estimating the change in load on the tire and wheel assembly of a trailer caused by its connection to a stationary tractor, the method comprising the steps of: In the preparatory stage • At least one pressure sensor is provided for at least one tire wheel assembly on at least one axle of a trailer not connected to a tractor, the sensor being capable of measuring the internal pressure of the fluid cavity of the tire wheel assembly defined by the tire and the wheel. Preferably, at least one pressure sensor is provided for at least one tire wheel assembly on each axle of the trailer. More preferably, at least one pressure sensor is provided for all tire wheel assemblies on all axles of the trailer. • Determine the initial load Z1 applied to at least one tire wheel assembly equipped with a pressure sensor on an unattached trailer; • Determine the initial inflation pressure P1 of the fluid chamber of at least one tire wheel assembly of the trailer equipped with a pressure sensor; • Determine the initial internal temperature T1 of the fluid cavity of at least one tire wheel assembly of the trailer equipped with a pressure sensor; • The initial volume V1 of the fluid cavity of at least one tire-wheel assembly equipped with a pressure sensor is evaluated using a first function, the parameters of which include the volume V0 of the fluid cavity of the tire-wheel assembly when unloaded and inflated to an initial pressure P1, and the flattening stiffness K of the tire per unit volume of the tire-wheel assembly. P ; • The number of fluid moles n in the fluid chamber of each tire wheel assembly equipped with a pressure sensor was evaluated using a model that takes into account inflation pressure P1, initial volume V1, and temperature T1. • Determine the evolution of the internal temperature T of the fluid cavity based on the internal pressure P during the adiabatic transition of at least one tire wheel assembly that is inflated, subjected to a load Z1, and equipped with at least one pressure sensor. During the main phase: • Connect the trailer to the vehicle at the trailer's geometric point M; • Record the internal pressure P of the fluid cavity of at least one tire wheel assembly equipped with a pressure sensor at a sampling frequency F1; • The internal temperature T of the fluid cavity of at least one tire wheel assembly equipped with a pressure sensor is determined by utilizing the evolution law determined in the preparatory stage; • By utilizing the recorded internal pressure P and the determined internal temperature T, the intermediate change ΔV of the volume of at least one tire wheel assembly equipped with a pressure sensor is evaluated using a model of a fluid undergoing an adiabatic transition, where the fluid behaves as an ideal gas. The load variation ΔZ borne by each tire-wheel assembly equipped with a pressure sensor is estimated using a second function, the parameters of which include the intermediate volume variation ΔV of the assessed volume and the flattened stiffness K per unit volume of the tire in the tire-wheel assembly. P .

2. The method for estimating the change in load on the tire and wheel assembly of a trailer caused by its connection to a stationary tractor, as described in claim 1, wherein, In the preparation phase, at least one tire wheel assembly equipped with a pressure sensor on at least one axle of the trailer includes a temperature sensor capable of measuring the temperature of a fluid cavity. The method includes a step in the main phase of recording the internal temperature T of the fluid cavity of at least one tire wheel assembly equipped with a pressure sensor at a sampling frequency F2. The method includes a second step of taking into account the recorded internal temperature T and using a model of a fluid that behaves as an ideal gas and is in thermal equilibrium with the environment outside the fluid cavity to evaluate an intermediate change ΔV2 in the volume of at least one tire wheel assembly equipped with a pressure sensor.

3. The method for estimating the change in load on the tire and wheel assembly of a trailer caused by its connection to a stationary tractor, as described in claim 1 or 2, wherein, Prior to the main steps, at least one tire-wheel assembly equipped with a pressure sensor is in a state of thermomechanical stability.

4. The method for estimating the change in load on the tire and wheel assembly of a trailer caused by its connection to a stationary tractor, according to any one of claims 1 to 3, wherein, The pressure sensor and / or temperature sensor are located in a subspace of a closed fluid cavity defined by the tire outer tube and wheel.

5. The method for estimating the change in load on the tire and wheel assembly of a trailer caused by its connection to a stationary tractor, according to any one of claims 1 to 4, wherein, The sampling frequency F1 is between 0.1Hz and 10Hz.

6. The method for estimating the change in load on the tire and wheel assembly of a trailer caused by its connection to a stationary tractor, according to any one of claims 2 to 5, wherein, The sampling frequency F2 is lower than the sampling frequency F1.

7. The method for estimating the change in load on the tire and wheel assembly of a trailer caused by its connection to a stationary tractor, according to any one of claims 1 to 6, wherein, The determination of the initial volume V0 takes into account the geometry of the rim and the geometry of the unloaded tire mounted on the rim and inflated to pressure P0. Preferably, P0 is the initial pressure P1.

8. The method for estimating the change in load on the tire and wheel assembly of a trailer caused by its connection to a stationary tractor, as described in claim 7, wherein, The geometry of the tire and / or the rim is determined using the tire and / or wheel identifiers of the tire and / or wheel assembly equipped with pressure sensors. Preferably, the tire and / or wheel identifiers are obtained by radio frequency interrogation of electronics located on the tire and wheel assembly.

9. The method for estimating the change in load on the tire and wheel assembly of a trailer caused by its connection to a stationary tractor, according to any one of claims 1 to 8, wherein, The load Z on each tire-wheel assembly equipped with a pressure sensor can be estimated using the following formula: [Formula 1] Among them, K PP It is the aerodynamic flattening stiffness per unit volume of the tire in the tire-wheel assembly.

10. The method for estimating the change in load on the tire and wheel assembly of a trailer caused by its connection to a stationary tractor, according to any one of claims 1 to 9, wherein, The volume change ΔV of each tire-wheel assembly equipped with a pressure sensor is estimated by solving the following differential equation: [Formula 2] [Formula 3] Where P is the internal pressure of the fluid cavity, V is the internal volume of the fluid cavity, and T is the internal temperature of the fluid cavity.

11. A method for estimating the load borne by a trailer securely connected to a vehicle, comprising a method for estimating the change in load borne by the tire wheel assembly of the trailer resulting from the trailer being connected to a stationary vehicle, according to any one of claims 1 to 10, characterized in that, in a preliminary stage, the method includes determining a first load distribution on each axle of the trailer in relation to the application of an additional load applied to the attachment point M where the trailer is connected to the vehicle, preferably, the first load distribution on each tire wheel assembly of the trailer; the method optionally further includes determining a second load distribution on each axle of the trailer in relation to the weight of the trailer, preferably, the second load distribution on each tire wheel assembly of the trailer; in a main stage, the method includes utilizing at least one equipped with pressure The method involves estimating the load Z borne by each tire wheel assembly of each axle i of the trailer by determining the change ΔZ of the load borne by the tire wheel assembly of the force sensor, the first load distribution related to the application of additional load at the attachment point M, and the initial load Z1i of each tire wheel assembly of the trailer. Optionally, the method further includes estimating the load Z borne by each tire wheel assembly by considering a second load distribution related to the weight of the trailer. The method also includes comparing the estimated load Z borne by each axle i of the trailer and / or the total load borne by the trailer with at least one threshold S, where the total load is the sum of the loads borne by each axle i of the trailer. When the at least one threshold S is exceeded, in a secondary stage, the mass content K of the trailer is modified, and then all the steps of the primary stage are performed again.

12. A system (2000) for implementing the method for estimating the change in load borne by a tire and wheel assembly of a trailer rigidly connected to a vehicle as caused by the connection of a trailer to a stationary vehicle, according to any one of claims 1 to 10, and / or for implementing the method for estimating the load borne by a trailer rigidly connected to a vehicle according to claim 11, the system comprising: • Trailer (2001), with a hook-up device installed at point M on the trailer, the hook-up device being able to accommodate the towing seat of the vehicle, and each axle i of the trailer including at least one tire wheel assembly (2006) equipped with an electronic device (2007). • The electronic device (2007) includes at least one pressure sensor, at least one electronic chip, at least one storage space capable of recording signals from the sensor, and at least one first radio frequency communication device (2101) capable of transmitting. • At least one computing device (2002); and • At least one display device (2003) includes at least one second radio frequency communication device (2102) capable of receiving.

13. The system (2000) for implementing the method for estimating the load variation borne by the tire wheel assembly of a trailer rigidly connected to a vehicle, as described in claim 12, and / or for implementing the method for estimating the load borne by a trailer rigidly connected to a vehicle, wherein, The system (2000) includes an analysis device (2004) capable of analyzing the results output by the at least one computing device (2002).

14. The method for estimating the load variation borne by a tire wheel assembly of a trailer rigidly connected to a vehicle, as claimed in any one of claims 12 and 13, and / or the system for estimating the load borne by a trailer rigidly connected to a vehicle (2000), wherein, The at least one computing device (2002) includes at least one third radio frequency communication device (2103) capable of transmitting / receiving.

15. The system (2000) for implementing the method for estimating the load variation borne by the tire wheel assembly of a trailer rigidly connected to a vehicle, as described in claim 14, wherein, The at least one analysis device (2004) includes at least one fourth radio frequency communication device (2104) capable of transmitting / receiving.

16. The method for estimating the load variation borne by a tire-wheel assembly of a trailer rigidly connected to a vehicle, as claimed in any one of claims 12 to 15, and / or the system for estimating the load borne by a trailer rigidly connected to a vehicle (2000), wherein, The system (2000) includes at least one reading device (2005) capable of reading data contained in at least one storage space of the electronic device (2007), and includes at least one fifth communication device (2105) capable of receiving data.

17. A system (2000) for implementing a method for estimating the load variation borne by a tire-wheel assembly of a trailer rigidly connected to a vehicle, according to any one of claims 12 to 16, wherein, Communication performed by the communication devices (2101, 2102, 2103, 2104, 2105) between a portion of the communication and the elements included in the group comprising the electronic device (2007), the at least one computing device (2002), the at least one display device (2003), the at least one analysis device (2004), and the at least one reading device (2005) is performed using UHF radio waves, preferably using BLE.

18. A method for estimating the load variation borne by a tire-wheel assembly of a trailer rigidly connected to a vehicle, as claimed in any one of claims 12 to 17, and / or a system for estimating the load borne by a trailer rigidly connected to a vehicle (2000), wherein, The at least one display device (2003) is included in the group comprising a telephone, a computer, and a human-machine interface located on a trailer (2001) and / or vehicle, preferably on a vehicle dashboard.

19. A method for estimating the load variation borne by a tire-wheel assembly of a trailer rigidly connected to a vehicle, as claimed in any one of claims 12 to 18, and / or a system for estimating the load borne by a trailer rigidly connected to a vehicle (2000), wherein, A portion of the at least one reading device (2005) is located on the trailer (2001).

20. The method for estimating the load variation borne by a tire-wheel assembly of a trailer rigidly connected to a vehicle, as claimed in any one of claims 12 to 19, and / or the system for estimating the load borne by a trailer rigidly connected to a vehicle (2000), wherein, A portion of the at least one computing device (2002) and / or a portion of the at least one analysis device (2004) is located on the trailer (2001), preferably on the tire wheel assembly (2006).

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