A method for estimating volume changes in an expandable system subjected to external forces.

Abstract

Disclosed is a method for estimating the variation in the volume ΔV of an inflatable system resulting from an external force applied to a stationary inflatable system, the method comprising the steps of: applying an external force F to a deformable surface of the inflatable system; recording the internal temperature T in the fluid cavity of the equipped inflatable system at an acquisition frequency F1; recording the internal pressure P in the fluid cavity of the equipped inflatable system at a frequency F2; and evaluating the variation in the volume ΔV of the equipped inflatable system using the recorded internal temperature T and recorded internal pressure P, using a fluid model in an adiabatic change in which the fluid exhibits perfect gaseous behavior.

Description

Technical Field

[0001] The present invention relates to the field of determining in real time the quasi-static volume variations of an inflatable system due to load variations resulting from the application of an external force to the inflatable system.

Background Art

[0002] Obtaining volume variations of an inflatable system through the application of an external force to the inflatable system enables determining new stability conditions of the inflatable system, or put differently, its new functional equilibrium point. Knowledge of this new equilibrium point enables identifying new functional characteristics of the inflatable system and, for that purpose, predicting its thermo-mechanical function in its usage context within a more complex system. That is, with respect to an automobile, the tires or the air suspension will change their thermo-mechanical properties as a function of volume variations brought about by the application of an external force to the vehicle, such as by connecting a trailer to the vehicle or passengers boarding the vehicle. That is, knowledge of the thermo-mechanical properties of the tires, such as the dynamic stiffness of the tires, is desirable in order to optimize the functional components of the vehicle, which can increasingly be set electronically, as it enables adapting the laws governing the evolution of certain components of the vehicle to these thermo-mechanical properties to improve the comfort of the occupants and / or the behavior of the vehicle. To date, the set values of these devices in vehicles are fixed values that depend on the degree of wear and aging of the tires or the air suspension, and this approach is not optimal in all situations and over time. Here, with respect to inflatable systems, their thermo-mechanical properties depend on pressure, temperature, and the volume occupied by the fluid within these inflatable systems. Temperature and pressure measurements are readily accessible by dedicated sensors, but it is not easy to measure the change in volume of the fluid cavities of these inflatable systems.

Summary of the Invention

Problems to be Solved by the Invention

[0003] The present object and method of the present invention aim to solve the problem of measuring volume changes in an inflatable system in the absence of an external measuring system, that is, in the inflatable system itself, which can be used at any time without specific measuring means. Furthermore, this evaluation is performed instantaneously, making it possible to quickly determine whether an inflatable system is in safe conditions, even before it starts moving, for example, whether the load supported by the tires of a vehicle is safe. [Means for solving the problem]

[0004] The present invention relates to a method for estimating the volume change ΔV of an expandable system caused by the application of an external force to the expandable system while it is at rest, and includes the following steps: ●In the preliminary phase, The step of equipping the expandable system with at least one temperature sensor capable of measuring the internal temperature of the fluid cavity of the expandable system, whose boundaries are defined by at least one deformable surface of the expandable system; The step of equipping the expandable system with at least one pressure sensor capable of measuring the internal pressure of the fluid cavity of the expandable system; • The step of determining the initial load Z1 applied to the deformable surface of the expandable system; • The step of determining the initial expansion pressure P1 of the fluid cavity of the expandable system; • The step of determining the initial internal temperature T1 of the fluid cavity of the expandable system; Among the parameters, the volume V0 of the fluid cavity of the expandable system when it expands to an initial pressure P1 under no load, and the stiffness K of the deformable surface of the expandable system per unit volume are particularly important. P A step in which the initial volume V1 of the fluid cavity of the expandable system is evaluated using a first function that includes ; The step of evaluating the number of moles n of fluid in the fluid cavity of the equipped expandable system using a model that takes into account the expansion pressure P1, initial volume V1, and temperature T1; ●During the main phase, • The step of applying an external force to the deformable surface of an expandable system; • Steps to obtain and record the internal temperature T of the fluid cavity of the equipped expandable system at frequency F1; The step of recording the internal pressure P of the fluid cavity of the equipped expandable system at frequency F2; and The step of evaluating the volume variation ΔV of the equipped expandable system using a fluid model in which the fluid is undergoing an adiabatic change in which the fluid behaves as an ideal gas, using the recorded internal temperature T and recorded internal pressure P.

[0005] In a first preferred embodiment, the preliminary phase of the method includes determining a law that gives rise to the progression of the internal pressure P of a fluid cavity based on the internal temperature T of the fluid in the fluid cavity of an expanded expandable system subjected to a load Z1; the main phase of the method includes extracting fluctuations in the internal temperature T' caused by the adiabatic change of the fluid solely from recordings of the internal temperature T; the method includes determining the internal pressure P' of the fluid cavity of the expandable system based on the internal temperature T' and the progression law determined in the preliminary phase; and the step of evaluating the volume variation ΔV of the expandable system includes a first phase in which the evaluation is performed using the extracted internal pressure P' and the determined internal temperature T', and at least a second phase in which the evaluation is performed using a portion of the recorded internal pressure P and a portion of the recorded internal temperature T recorded outside the time frame corresponding to the extracted fluctuations in internal pressure P'.

[0006] In another preferred embodiment, the preliminary phase of the method includes determining a law that gives rise to the progression of the internal temperature T of a fluid cavity based on the internal pressure P during the adiabatic change of the fluid in the fluid cavity of an expanded expandable system subjected to a load Z1; the main phase of the method includes extracting fluctuations in the internal temperature P' caused by the adiabatic change of the fluid solely from recordings of the internal pressure P; the method includes determining the internal temperature T' of the fluid cavity of the expandable system based on the internal pressure P' and the progression law determined in the preliminary phase; and the step of evaluating the volume fluctuation ΔV of the expandable system includes a first phase in which the evaluation is performed using the extracted internal temperature T' and the determined internal pressure P'; and at least a second phase in which the evaluation is performed using a portion of the recorded internal temperature T and a portion of the recorded internal pressure P, recorded outside the time frame corresponding to the extracted fluctuations in the internal temperature T'.

[0007] The method for determining volume variation involves two consecutive phases. The first phase consists of identifying the intrinsic parameters of the expandable system before the application of an external force. This involves setting up the expandable system measurement system through the attachment of the measuring device and the identification of initial parameters of the expandable system, such as the volume of the fluid cavity, the amount of fluid confined in the closed volume defined by the fluid cavity, the initially applied load, the internal temperature of the fluid cavity, and the expansion pressure of the fluid cavity. Intuitively, it is assumed that the properties of the fluid are known when estimating the amount of fluid trapped in the fluid cavity. When the system is under operating conditions, in particular, with a load Z1 near the expansion pressure P1 and temperature T1, it is also optionally necessary to have an evolution law that links the relevant variation in internal temperature T to the variation in the expansion pressure P of the expandable system with respect to the adiabatic change of the fluid. This evolution law may be a default law or may be derived from experimental characterization or numerical simulation of the eelset in question.

[0008] The second phase represents the stage of evaluating the fluctuations in the inflatable system equipped with electronic devices as a result of the application of an external force. One or more electronic devices include pressure sensors and temperature sensors, and manage and adjust the recording of the measured values. That is, the recording of the expansion pressure and internal temperature of the fluid cavity of the inflatable system equipped with electronic devices is performed at the moment of application of the external force. The temporal evolution of the physical quantities associated with the fluid cavity in the transient phase is large. The application of an external force to the inflatable system brings about a first change corresponding to the work done by this external force, which can be likened to an adiabatic, i.e., rapid change, and is even more significantly than the second change. Following the rapid change, a change follows that corresponds to the fluid cavity establishing thermal equilibrium with the external environment through the inflatable system. This equilibrium is necessary after the change in the internal temperature of the fluid cavity associated with the change connected to the work. This thermal equilibrium takes longer to establish due to the thermal inertia of the inflatable system. In addition, thermal equilibrium has a less significant effect on fluctuations in the volume of the fluid cavity than changes connected to work performed by external forces. As a result, it is possible to use different sampling frequencies for the physical quantity, temperature, and pressure. However, it is equally possible to use the same sampling frequency for both sensors. Preferably, the electronic device is fixed to the inner wall of the expandable system. This is because it is actually the expandable system that deforms the most during adiabatic changes. Furthermore, since the temperature sensor is far away from the metal components, the relative temperature fluctuations are large compared to the measured absolute temperature because the thermal inertia of the walls of the expandable system is lower than that of the metal components, which have greater inertia than those of the elastomer material of the deformable walls. As a result, the accuracy of temperature measurement and therefore the quality of this method for measuring volume fluctuations are improved.

[0009] In the first option, in cases where sampling of internal temperature records is insufficient to capture the first change, it is possible to use fluctuations in the expansion pressure of the fluid cavity to determine fluctuations in the internal temperature of the fluid in the fluid cavity, which are determined for this purpose using a predetermined progression law in a preliminary phase. This law thus translates the measurement of the internal pressure of the fluid in the fluid cavity to the evaluation of the internal temperature of the fluid, which occurs only due to changes connected to the work done by an external force.

[0010] In another first option, in cases where sampling of internal pressure records is insufficient to capture the first change, it is possible to use fluctuations in the internal temperature of the fluid cavity to determine fluctuations in the internal pressure of the fluid in the fluid cavity, which are determined for this purpose using a predetermined progression law in a preliminary phase. This law thus translates the measurement of the internal temperature of the fluid in the fluid cavity to an assessment of the internal fluid pressure that arises only from changes connected to work done by an external force.

[0011] Next, it is possible to evaluate the intermediate volume fluctuations using a model of a fluid undergoing adiabatic change. Here, the term adiabatic means that the change the fluid undergoes as a result of the application of an external force occurs without heat exchange between the fluid cavity and the outside of the expandable system, and this assumes that this change is abrupt. In either case, records of the internal pressure and especially the internal temperature provide information about the thermal equilibrium between the fluid in the fluid cavity and the external environment for the expandable system. As a result, by using the measured fluctuations in the expansion pressure and measured fluctuations in the internal temperature of the fluid cavity, it is possible to estimate the volume fluctuations of the fluid cavity, which are caused by the application of an external force and the fluid has undergone adiabatic change. It is assumed that the fluid in a gaseous state within the cavity of the equipped wheelset is an ideal gas, which is a perfectly reasonable assumption for air or nitrogen.

[0012] Preferably, a model of a fluid undergoing adiabatic change can be used to evaluate the first intermediate fluctuation in volume. As a result, by focusing on the first change in the fluid related to the work associated with the application of an external force, it is possible to estimate the first volume fluctuation of the fluid cavity caused by the application of an external force to a fluid undergoing adiabatic change by using fluctuations in measured expansion pressure, using only measurement points corresponding to the first change in the fluid, and using fluctuations in internal temperature determined using a predetermined progression law in the preliminary phase. Of course, if the acquisition frequency of internal pressure records is not sufficient to accurately capture the first change in the fluid, and the acquisition frequency of internal temperature records is higher, it is preferable to limit the internal temperature records to measurement points corresponding to the first change in the fluid and determine the internal pressure from a predetermined progression law (in which the internal temperature records are input) in the preliminary phase.

[0013] Preferably, a second intermediate variation in volume is assessed using a second change in the fluid. This second change relates to the thermal equilibrium between the fluid and the external environment, primarily through the deformable surfaces of the components of the expandable system. Next, the second variation in volume experienced by the expandable system in this second change is assessed using the recorded internal temperature variation recorded within the fluid cavity, which occurs during the transient phase associated with the application of an external force, but following the change associated with the work done by this external force. By considering this second variation in volume, better accuracy is ensured in the assessment of the variation in the fluid cavity volume, thereby improving the accuracy of measuring the variation in volume of the expandable system. Still, the first intermediate variation in volume is sufficient to estimate the variation in volume associated with the application of an external force to the nearest tenth of an magnitude.

[0014] Of course, by considering the temperature fluctuations outside the expandable system from which the thermal equilibrium of the wheelset is obtained, it is possible to refine the measurement accuracy of the second volume fluctuation caused by the application of an external force. However, in a simpler method, since it is preferable that the expandable system is in a thermomechanically stable state, it is possible to consider the initial internal temperature T1 of the fluid in the fluid cavity of the expandable system through the external temperature.

[0015] These two changes may occur in each time interval or sequentially over the duration of the time measurement. Evaluation of these intermediate volume fluctuations must be performed using measurements from the vehicle's load transient to the time at which mechanical, and in some cases thermal, equilibrium is established in the vehicle wheelset. Once these equilibrium states are established, the temperature and pressure fluctuations in the fluid cavity become infinitesimally small, and a further thermally stable state is reached.

[0016] Optionally, with the intermediate volume variation of the expandable system evaluated, the associated static load variation resulting from the application of an external force to the expandable system must be evaluated. To do this, the volume variation of the expandable system must be converted into an equivalent load variation. For this purpose, the properties of the expandable system, in particular the deformable surface, i.e., K SGIt is appropriate to consider the stiffness per unit volume of the deformable surface of the expandable system. This quantity provides a relationship between the force applied by the expandable system and the volume variation of the fluid cavity caused by the applied external force, and the expandable system is flattened on the surface that responds to the applied force. This property can, of course, be a default quantity, or it can be obtained by experimental characterization of the expandable system or inferred by a strategy of numerical simulation of the same expandable system. The expandable system needs to be under operating conditions close to those observed in the preliminary phase, i.e., around the internal temperature T1 and expansion pressure P1. Generally, this stiffness of the expandable system is a quantity determined locally near the initial operating point of the expandable system in a coordinate system associated with the internal pressure P, internal temperature T, and fluid cavity volume V.

[0017] Advantageously, the extraction of fluctuations in internal temperature T' ends when the recorded internal temperature T changes direction of fluctuation, or at the end of duration T0 corresponding to the end of the adiabatic change of the fluid.

[0018] Advantageously, the extraction of fluctuations in internal pressure P' ends when the recorded internal pressure P changes direction of fluctuation, or at the end of time T0 corresponding to the end of the adiabatic change of the fluid.

[0019] Preferably, prior to the main stage, at least one equipped expandable system is in a thermally and mechanically stable state.

[0020] Preferably, transient phenomena recorded by the sensor of an electronic device can be attributed solely to disturbances in the equilibrium of the expandable system caused by the application of an external force. That is, other disturbances do not affect the sensor's response, thereby improving the accuracy of volume fluctuations evaluated using this method. However, even if the disturbance to the equilibrium of the expandable system occurs on a different time scale than the disturbance associated with the application of the external force, or if this disturbance appears in the sensor's response of the electronic device as a smaller amplitude, this method remains perfectly appropriate.

[0021] Advantageously, the pressure sensor and / or the temperature sensor are placed in a partial space of a closed fluid cavity bounded by the deformable surface of the inflatable system.

[0022] Sensors for measuring low-amplitude transients are advantageously positioned close to where these transients occur so as not to be buried in measurement noise. That is, it is advantageous for the sensor to be located on the deformable surface of the inflatable system. Finally, preferably, the sensor, particularly the temperature sensor, is positioned so as to be far from non-deformable components generally made of metal, which has a higher thermal inertia than the deformable surface conventionally made of an elastomeric material.

[0023] Advantageously, the temperature sensor operates with a resolution better than 0.01 degrees.

[0024] Advantageously, the temperature sensor operates with a resolution better than 1 millibar.

[0025] That is, it is possible to evaluate small variations in volume and thus small variations in load.

[0026] According to one particular embodiment, the determination of the initial volume V0 takes into account the shape of the deformable surface of the inflatable system inflated to the reference pressure P0, and the reference pressure P0 is preferably the initial pressure P1.

[0027] Advantageously, the shape of the deformable surface is determined using an identifier of the inflatable system, and the identifier of the inflatable system is preferably obtained by radio frequency interrogation of an electronic device positioned on the inflatable system.

[0028] To initialize the measurement system, particularly for determining the initial volume V1 of the fluid cavity, it is appropriate to determine the volume V0 of the fluid cavity corresponding to the volume defined by the deformable surface when the deformable surface is unloaded, i.e., when the deformable surface is mounted on the expandable system at a reference expansion pressure P0, which is preferably the initial pressure P1.

[0029] To determine this volume V0, it is necessary to know the shape of the fluid cavity relative to the reference expansion pressure P0 for an unloaded inflatable system. This shape is available through a database of inflatable systems. Knowledge of the ID of the inflatable system allows for the identification of the correct shape in this database. The ID of the inflatable system can be obtained by optically reading a marking attached to the outside of the inflatable system. Alternatively, this ID can be transmitted by radio frequency querying of an electronic device present on the inflatable system, such as an RFID (Radio Frequency Identification) tag.

[0030] Preferably, the load Z on the expandable system is estimated by the first relationship in the following equation:

number

[0031] This is a simple and rudimentary model that links the load applied to an inflatable system to the change in the volume of the fluid cavity between the unloaded volume V0 and the loaded volume V1, the expansion pressure P of the fluid cavity, and the aerodynamic stiffness of the inflatable system corresponding to the flattening of the inflatable system on a plane. Throughout this model, it is assumed that the structural stiffness of the inflatable system is negligible compared to the aerodynamic stiffness, and this assumption is a realistic assumption commonly made for inflatable systems. However, it is entirely possible to incorporate structural stiffness into the above equation by adding structural stiffness to the product of aerodynamic stiffness and expansion pressure.

[0032] In one advantageous embodiment, the variation ΔV of the volume of the fluid cavity of the equipped inflatable system is given by the following differential equation:

number

number

[0033] This differential equation illustrates the link between parameters of the fluid within the cavity of an expandable system, which are governed, firstly by the adiabatic change of the fluid, and secondly by the fact that the fluid is an ideal gas.

[0034] The present invention also relates to the use of a method for estimating the volume change ΔV of an inflatable system caused by applying an external force to the inflatable system while it is stationary, the inflatable system includes the group of air tire casings, air shock absorbers, or centralized tire inflation systems.

[0035] These are examples of applications of this method to industrial purposes characterized by aerodynamic rigidity and susceptibility to external forces.

[0036] The present invention also relates to a method for evaluating a load variation ΔZ applied to an inflatable system, which includes a method for evaluating a volume variation ΔV, the method comprising the step of determining the load variation ΔZ using a function F in which at least one parameter is the volume variation ΔV of the fluid cavity of the inflatable system, the function F being given by the following equation:

number

[0037] One application of this method is to obtain variations in the load applied to an inflatable system. For this purpose, it is appropriate to consider the properties of the inflatable system, particularly the properties of the deformable surface, i.e., the flattening stiffness KSG per unit volume. This quantity provides a relationship between the load on the inflatable system and the variation in the volume of the fluid cavity caused by the load, so that the inflatable system is flattened perpendicular to the ground with respect to the applied load. This property can, of course, be a default quantity, or it can be obtained by experimental characterization of the inflatable system or inferred by a strategy of numerical simulation of the same inflatable system. The inflatable system needs to be under operating conditions close to those observed in the preliminary phase, i.e., around the internal temperature T1 and expansion pressure P1. Generally, this flattening stiffness of the inflatable system is a quantity determined locally near the initial operating point of the inflatable system in a coordinate system associated with the internal pressure P, internal temperature T, and fluid cavity volume V.

[0038] The present invention will be better understood by reading the following description, which is given solely by non-limiting embodiments and which refers to the accompanying drawings throughout which the same reference numerals represent the same parts. [Brief explanation of the drawing]

[0039] [Figure 1] This is a block diagram of a method for estimating the volume change ΔV of an expandable system caused by the application of an external force, according to the present invention. [Figure 2] This figure shows the temporal evolution of the internal temperature of a fluid cavity as output by a temperature sensor. [Figure 3] This figure shows the temporal evolution of the internal pressure of a fluid cavity as output by a pressure sensor. [Figure 4] This figure presents an estimated value regarding the time of volume variation in a fluid cavity according to the present invention. [Figure 5]This figure presents estimates of the time fluctuations in the load on the vehicle's wheelset associated with the trailer's attachment to the vehicle. [Modes for carrying out the invention]

[0040] Figure 1 shows a block diagram of a method for estimating the volume change ΔV of an expandable system caused by the application of an external force to the expandable system while it is at rest. This method includes several phases.

[0041] The first is a preliminary phase, which includes at least actions 1 through 6, which are performed sequentially through a linking system drawn with solid lines. This preliminary phase focuses on the inflatable system before the application of external forces and naturally includes the step of equipping the inflatable system by attaching pressure and temperature sensors that can measure the internal pressure and internal temperature of the fluid cavity, whose boundaries are defined by deformable surfaces, using dedicated electronic devices. The first steps, denoted as 1 and 2, consist of determining physical quantities associated with the fluid cavity of the inflatable system equipped with measuring devices, such as expansion pressure P1 and internal temperature T1. Preferably, these determinations are made by taking default values ​​or specific measurements. The step denoted as 3 consists of determining the load Z1 carried by the inflatable system equipped with measuring devices. This determination can be made by taking default values ​​or by evaluating specific measurements. The step referred to as 4 corresponds to the step of obtaining specific quantities from the inflatable system equipped with measuring devices. One of these quantities is volume V0, which corresponds to the volume occupied by the fluid cavity when the expandable system expands to pressure P1, strictly speaking, at an internal temperature T1 but without any bearing load, i.e., when not in contact with the ground. The second quantity is the flattening stiffness K per unit volume of the expandable system. PThis may depend on the expansion pressure P1, internal temperature T1, and supported load Z1. Finally, the third set of quantities is related to the laws governing the behavior of an ideal gas for the properties of the gas confined in the fluid cavity of the expandable system. In addition to this, the second to last stage of the preliminary phase (reference number 5) is the stage of determining the volume V1 occupied by the fluid cavity of the instrumented expandable system under load Z1, expansion pressure P1, and temperature T1. Finally, the last stage of the preliminary phase, denoted as 6, is the stage of evaluating the amount of gas confined in the fluid cavity of the instrumented expandable system by determining the number of moles n of gas present in volume V1. Here, although the assumptions associated with the ideal gas condition certainly apply, it is still necessary to identify the properties of the gas composition, i.e., whether it is a single gas or a mixture of gases. In addition, optionally, even if not shown in this preliminary phase, it is important to determine the progression law that links the fluctuations in internal pressure P to the fluctuations in internal temperature T for the fluid in the fluid cavity during an adiabatic change near the operating point of the expandable system, i.e., near pressure P1, temperature T1, and load Z1.

[0042] This method then proceeds to the main stage, which begins with the application of an external force to the inflatable system. Consequently, the time variation of the expansion pressure P(t) and internal temperature T(t) of the inflatable system is recorded, with an accuracy of approximately 1 millibar for the pressure sensor and approximately 0.01 degrees for the temperature sensor, when used with passenger cars and trailers suitable for this type of vehicle. These records are then stored in memory, and the raw data can be filtered using a low-pass filter to remove high-frequency phenomena, which corresponds to step 11 for pressure and step 12 for temperature.

[0043] Optionally, in cases where the frequency of recording the internal temperature is insufficient to capture the first change in the fluid, the time variation of the internal temperature T(t) of the fluid cavity is determined from the time variation of the internal pressure P(t) using the progression law determined in the preliminary stage, which corresponds to stage 12. Conversely, if the sampling frequency for recording the internal pressure p(t) is insufficient to capture the first change in the fluid, the variation in internal pressure is determined from the variation in internal temperature using the progression law that links the two quantities during the adiabatic change.

[0044] In this method, the connection system between optional and essential stages is shown using gray lines, not black. However, connection lines belonging to the main phase are shown as dotted lines, while those belonging to the preliminary phase are shown as solid lines. Finally, as will be discussed later, secondary phases have a connection system depicted as dashed (dotted) lines.

[0045] One of the key steps in the main phase is the step of determining the volume variation ΔV of the fluid cavity of the instrumented expandable system throughout step 13. This corresponds to considering, at least, the change in the fluid in the fluid cavity associated with the work associated with the application of an external force. However, this also considers a second change in the fluid associated with the thermal equilibrium between the fluid in the fluid cavity and the outside of the expandable system.

[0046] The fluctuations in internal pressure and internal temperature can be used to incorporate the above assumptions into the differential equation. By solving this differential equation in time segments, it is possible to obtain an estimate of the temporal volume change ΔV(t) of the relevant fluid cavity.

[0047] Optionally, another important step is to evaluate the variation ΔZ of the supported load, which is related only to the variation ΔV of the volume evaluated earlier, and this corresponds to step 14. For this purpose, the flattening stiffness K of the expandable system is SG Therefore, the flattening stiffness per unit volume of the deformable surface must be reconsidered.

[0048] Figure 2 shows the temporal evolution of temperature provided by a temperature sensor of an electronic device placed in an expandable system, in this example where an external force is suddenly applied as the vehicle wheelset, acting as a trailer, is coupled to the vehicle. The curve constituting point 10 represents the raw measurement from the temperature sensor, while curve 11 corresponds to the filtered temporal evolution of the internal temperature with high-frequency noise removed. This second curve will later be used in the block diagram in Figure 1.

[0049] This time-based record of the internal temperature of the wheelset fluid cavity begins in the preliminary phase before the trailer is coupled to the vehicle. The moment the trailer is coupled corresponds to the ax-coordinate value of point 100, which characterizes the start of the main phase. From point 100 onward, the internal temperature of the fluid cavity drops sharply to point 101, where the temperature drop stops and can even be observed to rise slightly. This point 101 characterizes the transition between the fluid work associated with the coupling of the trailer (corresponding to the first change in the fluid, which can be likened to an adiabatic change connected to the work generated by the application of an overload) and the heat exchange with the outside (corresponding to the second change in the fluid). The ax-coordinate value at point 101 corresponds to the duration T0, when the time origin is considered to be the ax-coordinate value of point 100. That is, the preliminary phase 50 ends at the ax-coordinate value of point 100. This phase precedes the main phase, which is divided into two consecutive phases. The first phase 51 can be likened to the adiabatic change of the fluid, corresponding to the work done by the fluid after the trailer is coupled to the vehicle. The second phase 52 corresponds to the heat exchange between the fluid and the outside.

[0050] Figure 3 shows the temporal evolution of the internal pressure of the fluid cavity for the same wheelset. Here, this temporal evolution is provided by pressure sensors of electronic devices located in the vehicle's wheelset, as shown in curve 12.

[0051] This progression of the internal temperature 12 of the wheelset fluid cavity begins in a preliminary phase before the trailer is coupled to the vehicle. The moment of coupling corresponds to the ax-coordinate value of point 100, which characterizes the start of the main phase. From point 100 onward, the internal pressure of the fluid cavity drops sharply to point 101, where the pressure drop stops and can even be observed to rise slightly. This point 101 characterizes the transition between the fluid work associated with the coupling of the trailer (corresponding to the first change in the fluid, which can be likened to an adiabatic change) and the heat exchange with the outside (corresponding to the second change in the fluid). The ax-coordinate value at point 101 corresponds to the duration T0, when the time origin is considered to be the ax-coordinate value of point 100. That is, the preliminary phase 50 ends at the ax-coordinate value of point 100. This phase precedes the main phase and can be divided into two consecutive phases. The first phase 51 can be likened to the adiabatic change of the fluid corresponding to the work done by the fluid after the trailer is coupled to the vehicle. The second phase, phase 52, corresponds to heat exchange between the fluid and the outside.

[0052] Figure 4 shows the temporal evolution of the internal volume of the fluid cavity. In this case, the temporal evolution represented by the curve is the output obtained by calculating the volume variation using a differential equation proposed that also takes thermal equilibrium with the external environment into consideration.

[0053] This progression of the internal volume of the fluid cavity in the wheelset begins in a preliminary phase before the trailer is coupled to the vehicle. The moment of coupling corresponds to the ax-coordinate value of point 100, which characterizes the start of the main phase. From point 100 onward, the internal volume of the fluid cavity increases rapidly up to point 101, where the increase in internal volume stops, and then it can be seen to decrease to some extent. This point 101 characterizes the transition between the fluid work associated with the coupling of the trailer (corresponding to the first change in the fluid, which can be likened to an adiabatic change) and the heat exchange with the outside (corresponding to the second change in the fluid). The ax-coordinate value at point 101 corresponds to the duration T0, when the time origin is considered to be the ax-coordinate value of point 100. That is, the preliminary phase 50 ends at the ax-coordinate value of point 100. This phase precedes the main phase, which can be divided into two consecutive phases. The first phase 51 can be likened to the adiabatic change of the fluid, which corresponds to the work done by the fluid after the passengers board. The second phase, phase 52, corresponds to heat exchange between the fluid and the outside.

[0054] At the end of Phase 51, a good estimate of the variation in the wheelset volume is obtained, which should be understood as clearly indicating that the work done by the variation in the load on the wheelset is primarily performed during Phase 51. The observed variation or oscillation corresponds to the transient phase fluctuations corresponding to the establishment of thermal equilibrium. As a result, the method described herein generates continuous measurements of the variation in the internal volume of the wheelset in the time domain.

[0055] Figure 5 shows the temporal evolution of load variations applied to the same wheelset equipped with electronic devices. In this case, the temporal evolution represented by curve 14 is the output obtained by calculating the volume variation using the proposed differential equation, which also takes into account thermal equilibrium with the external environment, and multiplying it by the flattening stiffness. In this case, the stiffness used is locally identified by the initial pressure on the wheelset, i.e., the initial load applied to the wheelset, and corresponds to the initial temperature. It would have been possible to adopt the overall stiffness determined by the proposed equation, which is already considered to have a good number of digits.

[0056] This progression of load 14 with respect to the fluid cavity of the wheelset begins in a preliminary phase before the trailer is coupled to the vehicle. The moment of coupling corresponds to the ax-coordinate value of point 100, which characterizes the start of the main phase. From point 100 onward, the load decreases sharply to point 101, corresponding to unloading, where the decrease in load stops, and then it can be seen to decrease to some extent. Point 101 characterizes the transition between the fluid work associated with the coupling of the trailer (corresponding to the first change in the fluid, which can be likened to an adiabatic change) and the heat exchange with the outside (corresponding to the second change in the fluid). The ax-coordinate value at point 101 corresponds to the duration T0, when the time origin is considered to be the ax-coordinate value of point 100. That is, the preliminary phase 50 ends at the ax-coordinate value of point 100. This phase precedes the main phase, which can be divided into two consecutive phases. The first phase 51 can be likened to the adiabatic change of the fluid corresponding to the work done by the fluid after the coupling of the trailer. The second phase, phase 52, corresponds to heat exchange between the fluid and the outside.

[0057] At the end of Phase 51, a good estimate of the variation in the load applied to the wheelset is obtained, which clearly indicates that the work generated by the load variation is primarily performed during Phase 51. The observed variation or vibration corresponds to the transient phase fluctuations corresponding to the establishment of thermal equilibrium. As a result, the method described herein generates continuous measurements of the time variation of the load applied to the wheelset in the time domain. Curve 80 corresponds to the measurement of the overload applied to the vehicle's wheelset, obtained from a ground-based weighing platform, which ensures that the estimate of the overload applied to the equipped wheelset is a reasonable estimate. In conclusion, the proposed method has a good grasp of the variation in the applied load. [Explanation of Symbols]

[0058] Cp (Specific Heat at Constant Pressure) Cv Specific heat at constant volume K P Flattening rigidity n: Number of moles of gas present in the initial volume P1 Initial expansion pressure

Claims

1. A method for estimating the volume change ΔV of an expandable system caused by the application of an external force to the expandable system while it is at rest, In the preliminary phase, - The step of equipping the expandable system with at least one temperature sensor capable of measuring the internal temperature of the fluid cavity of the expandable system, whose boundary is defined by at least one deformable surface of the expandable system. - The step of equipping the expandable system with at least one pressure sensor capable of measuring the internal pressure of the fluid cavity of the expandable system, - The step of determining the initial load Z1 applied to the deformable surface of the expandable system, - The step of determining the initial expansion pressure P1 of the fluid cavity of the expandable system, - A step of determining the initial internal temperature T1 of the fluid cavity of the expandable system, - The initial volume V1 of the fluid cavity of the expandable system, the volume V0 of the fluid cavity of the expandable system when expanded to the initial pressure P1 under no load, and the stiffness K of the expandable system per unit volume, among its parameters. P The first step is to evaluate using a function that includes the following: - A step of evaluating the number of moles n of fluid in the fluid cavity of the expandable system using a model that takes into account the expansion pressure P1, the initial volume V1, and the temperature T1. During the main phase, - The step of applying the external force to the deformable surface of the expandable system, - A step of recording the internal temperature T of the fluid cavity of the expandable system at acquisition frequency F1, - A step of recording the internal pressure P of the fluid cavity of the equipped expandable system at frequency F2, and - A step of evaluating the volume variation ΔV of the equipped expandable system by using the recorded internal temperature T and the recorded internal pressure P, using a model of the fluid undergoing an adiabatic change in which the fluid behaves as an ideal gas. A method that includes this.

2. The preliminary phase includes the step of determining a law that gives rise to the internal pressure P of the fluid cavity based on the internal temperature T of the fluid in the fluid cavity of the expanded expandable system subjected to the load Z1, The main phase includes a step of extracting the fluctuations in the internal temperature T' caused by the adiabatic change of the fluid from the record of the internal temperature T alone, The method includes the step of determining the internal pressure P' of the fluid cavity of the expandable system based on the internal temperature T' and the progression law determined in the preliminary phase, and the step of evaluating the variation ΔV of the volume of the expandable system includes a first phase in which the evaluation is performed using the extracted internal pressure P' and the determined internal temperature T', and at least a second phase in which the evaluation is performed using a portion of the recorded internal pressure P and a portion of the recorded internal temperature T, recorded outside the time frame corresponding to the extracted variation of the internal pressure P'. A method for estimating the volume fluctuation ΔV of an expandable system caused by the application of an external force to the expandable system while it is at rest, as described in claim 1.

3. The preliminary phase includes a step of determining a law that gives rise to the progression of the internal temperature T of the fluid cavity based on the internal pressure P of the fluid in the fluid cavity of the expanded expandable system subjected to the load Z1, The main phase includes a step of extracting the fluctuations in the internal pressure P' caused by the adiabatic change of the fluid from the record of the internal pressure P alone, The method includes the step of determining the internal temperature T' of the fluid cavity of the expandable system based on the internal pressure P' and the progression law determined in the preliminary phase, and the step of evaluating the variation ΔV of the volume of the expandable system includes a first phase in which the evaluation is performed using the extracted internal temperature T' and the determined internal pressure P', and at least a second phase in which the evaluation is performed using a portion of the recorded internal temperature T recorded outside the time frame corresponding to the extracted variation of the internal temperature T' and a portion of the recorded internal pressure P recorded outside the time frame. A method for estimating the volume fluctuation ΔV of an expandable system caused by the application of an external force to the expandable system while it is at rest, as described in claim 1.

4. A method for estimating a change in the volume ΔV of an expandable system caused by the application of an external force to the expandable system while it is at rest, according to claim 2, wherein the extraction of the fluctuation of the internal temperature T' is terminated when the recorded internal temperature T changes direction of fluctuation or at the end of a duration T0 corresponding to the end of the adiabatic change of the fluid.

5. A method for estimating a change in the volume ΔV of an expandable system caused by the application of an external force to the expandable system while it is at rest, according to claim 3, wherein the extraction of the fluctuation of the internal pressure P' is terminated when the recorded internal pressure P changes direction of fluctuation or at the end of a duration T0 corresponding to the end of the adiabatic change of the fluid.

6. A method for estimating the change in volume ΔV of the inflatable system caused by the application of an external force to the inflatable system at rest, according to one of claims 1 to 5, wherein, prior to the main step, the equipped inflatable system is in a thermally-mechanically stable state.

7. A method for estimating a change in the volume ΔV of an expandable system caused by the application of an external force to an expandable system while it is at rest, according to one of claims 1 to 6, wherein the temperature sensor and the pressure sensor are placed in a subspace of the closed fluid cavity whose boundary is defined by the deformable surface of the expandable system.

8. A method for estimating the volume fluctuation ΔV of an expandable system caused by the application of an external force to the expandable system while it is stationary, according to one of claims 1 to 7, wherein the temperature sensor operates with a resolution better than 0.01 degrees.

9. A method for estimating the volume fluctuation ΔV of an expandable system caused by the application of an external force to the expandable system while it is stationary, according to one of claims 1 to 8, wherein the pressure sensor operates with a resolution better than 1 millibar.

10. A method for estimating the change in volume ΔV of an expandable system caused by the application of an external force to an expandable system at rest, according to one of claims 1 to 9, wherein the determination of the initial volume V0 preferably takes into account the shape of the deformable surface of the expandable system when it has expanded to a reference pressure P0 which is the initial pressure P1.

11. A method for estimating the change in volume ΔV of an inflatable system caused by the application of an external force to an inflatable system while it is stationary, according to claim 10, wherein the shape of the deformable surface is preferably determined using an identifier of the inflatable system obtained by radio frequency querying of an electronic device located in the inflatable system.

12. The load Z on the aforementioned inflatable system is given by the following formula: [Math 1] It is estimated using the relationship, where K PP A method for estimating the volume fluctuation ΔV of an expandable system caused by the application of an external force to the expandable system while it is at rest, according to one of claims 1 to 11, wherein the air stiffness of the deformable surface of the expandable system per unit volume is the air stiffness of the deformable surface of the expandable system.

13. The variation ΔV of the volume of the fluid cavity of the equipped expandable system is given by the following differential equation: [Math 2] of [Math 3] A method for estimating the change in volume ΔV of an expandable system caused by the application of an external force to the expandable system at rest, according to one of claims 1 to 12, wherein P is the internal pressure, V is the internal volume, and T is the internal temperature of the fluid cavity, and is estimated by solving together with, where P is the internal pressure, V is the internal volume, and T is the internal temperature of the fluid cavity.

14. A method for evaluating the variation ΔZ of a load applied to an expandable system, comprising the method for evaluating the volume variation ΔV according to one of claims 1 to 13, A step in determining the variation ΔZ of the load by using a function F in which at least one parameter is the variation ΔV of the volume of the fluid cavity of the expandable system, wherein the function F is preferably given by the following equation: [Math 4] Determined by the relationship, where K SG However, the determination step is that the stiffness of the deformable surface of the expandable system per unit volume, A method that includes this.

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