WO2025003101A1 - Method for estimating the variation in the volume of an inflatable system subjected to an external force - Google Patents

Abstract

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

Description

DESCRIPTION

TITLE: METHOD FOR ESTIMATING THE VARIATION IN VOLUME OF AN INFLATABLE SYSTEM SUBJECTED TO AN EXTERNAL FORCE

Field of invention

[0001] The present invention relates to the field of real-time determination of the quasi-static volume variation of an inflatable system up to the load variation generated by the application of an external force to the inflatable system.

Technological background

[0002] Obtaining the volume variation of an inflatable system by applying an external force to the inflatable system makes it possible to determine the new stability condition of the inflatable system, in other words its new functional equilibrium point. Knowledge of this new equilibrium point makes it possible to identify the new functional characteristics of the inflatable system, thus making it possible to anticipate its thermomechanical capabilities in the context of its use within a more complex system. Thus, for an automobile, a tire or air suspension will change its thermomechanical properties depending on the volume variation generated by the application of an external force to the vehicle by coupling a trailer to the vehicle or boarding passengers within the vehicle. Thus, in order to optimize the functional organs of the vehicle, which are increasingly electronically configurable, knowledge of the thermomechanical properties of the tire, such as the dynamic rigidities of the tire, is desirable in order to adapt the laws of evolution of certain organs of the vehicle to these thermomechanical properties in order to improve passenger comfort and/or vehicle behavior. To date, the settings of these devices in vehicles are fixed according to the degree of wear and aging of the tire or air suspension, which is not optimal in all circumstances and over time. However, for an inflatable system, its thermomechanical properties are a function of the pressure, temperature and volume occupied by the fluid in these inflatable systems. While the measurement of temperature and pressure are easily accessible by dedicated sensors, the evolution of the volume of the fluid cavity of these inflatable systems is not easy.

[0003] The objects and methods of the invention which follow aim to solve the problem of measuring the variation in volume of an inflatable system in the absence of a measuring system external to the inflatable system, i.e. usable at any time without specific measuring means within the inflatable system. In addition, this evaluation is carried out instantly, allowing a rapid decision to be made on the safety criterion of the inflatable system, such as the load carried by a vehicle tire before any movement of the vehicle.

Description of the invention

[0004] The invention relates to a method for estimating the variation in AV volume of an inflatable system generated by the application of an external force to the stationary inflatable system comprising the following steps:

• In the preliminary phase,

• Equip the inflatable system with at least one temperature sensor, said sensor being capable of measuring the internal temperature of the fluid cavity of the inflation system delimited by at least one deformable surface of the inflatable system;

• Equip the inflatable system with at least one pressure sensor, said sensor being capable of measuring the internal pressure of the fluid cavity of the inflation system;

• Determine the initial load ZI exerted on the deformable surface of the inflatable system;

• Determine the initial inflation pressure PI of the fluid cavity of the inflatable system;

• Determine the initial internal temperature Tl of the fluid cavity of the inflatable system;

• Evaluate the initial volume VI of the fluid cavity of the inflatable system at T using a first function comprising as parameter the volume V0 of the fluid cavity of the unloaded inflatable system inflated to the initial pressure PI and the rigidity of the deformable surface of the inflatable system per unit volume Kp,

• Evaluate the number of moles of fluid n in the fluid cavity of the inflatable system equipped from a model taking into account the inflation pressure PI, the initial volume VI, the temperature Tl;

• In the main phase:

• Apply the external force on the deformable surface of the inflatable system; • Record the internal temperature T of the fluid cavity of the equipped inflatable system at an acquisition frequency Fl;

• Record the internal pressure P of the fluid cavity of the equipped inflatable system at a frequency F2; and

• Evaluate a variation in volume AV of the equipped inflatable system using the recorded internal temperature T and the internal pressure P recorded using a fluid model in adiabatic transformation, the fluid having ideal gas behavior.

[0005] According to a first preferred embodiment, in the preliminary phase, the method comprises a step of determining a law of evolution of the internal pressure P of the fluid cavity from the internal temperature T during an adiabatic transformation of the fluid of the fluid cavity of the inflatable system inflated and subjected to the load Zl, in the main phase, the method comprises a step of extracting the variations in internal temperature T' generated by the sole adiabatic transformation of the fluid from the recording of the internal temperature T, the method comprises a step of determining an internal pressure P' of the fluid cavity of the inflatable system from the internal temperature T' and the law of evolution determined in the preliminary phase and the step of evaluating the variation in volume AV of the inflatable system comprises a first phase where the evaluation is carried out with the extracted internal pressure P' and the determined internal temperature T' and at least a second phase where the evaluation is carried out with a portion of the internal pressure P recorded outside a time frame corresponding to the extracted internal pressure variations P' and a portion of the internal temperature recorded T outside of said time frame.

[0006] According to another first preferred embodiment, in the preliminary phase, the method comprises a step of determining a law of evolution of the internal temperature T of the fluid cavity from the internal pressure P during an adiabatic transformation of the fluid of the fluid cavity of the inflatable system inflated and subjected to the load Zl, in the main phase, the method comprises a step of extracting the variations in internal pressure P' generated by the sole adiabatic transformation of the fluid from the recording of the internal pressure P, the method comprises a step of determining an internal temperature T' of the fluid cavity of the inflatable system from the internal pressure P' and the law of evolution determined in the preliminary phase and the step of evaluating the variation in volume AV of the inflatable system comprises a first phase where the evaluation is carried out with the extracted internal temperature T' and the determined internal pressure P' and at least a second phase phase where the evaluation is carried out with a part of the internal temperature T recorded outside a time frame of the extracted internal temperature variations T' and a part of the recorded internal pressure P outside said time frame.

[0007] The method for determining the volume variation comprises two successive phases. The first phase consists of identifying the intrinsic parameters of the inflatable system before the application of the external force. This constitutes an installation of the measurement system of the inflatable system by means of the installation of measurement devices and the identification of the initial parameters of the inflatable system such as the volume of the fluid cavity, the quantity of fluid contained in the closed volume defined by the fluid cavity, the load initially applied, the internal temperature of the fluid cavity and the inflation pressure of the fluid cavity. Intuitively, the nature of the fluid is assumed to be known in order to estimate the quantity of fluid trapped in the fluid cavity. It is also optionally necessary to have an evolution law linking the variation in internal temperature T associated with the variation in inflation pressure P of the inflatable system for an adiabatic transformation of the fluid when it is in use conditions, in particular at the load ZI carried around the inflation pressure PI and the temperature TL. This evolution law can be fixed or derived from an experimental characterization or a numerical simulation of the assembled assembly considered.

[0008] The second phase represents the step of evaluating the variation of the inflatable system equipped with an electronic device due to the application of the external force. The electronic device(s) comprise the pressure sensor and the temperature sensor, manage and condition T recordings of the measurements. Thus, recordings of the inflation pressure and the internal temperature of the fluid cavity of the inflatable system equipped with an electronic device are made at the time of application of the external force. The temporal changes, in the transient phase, of the physical quantities of the fluid cavity are significant. The application of the external force on the inflatable system causes a first transformation corresponding to the work generated by this external force which is similar to an adiabatic transformation, i.e. rapid, which is moreover preponderant compared to the second transformation. This is followed, after the rapid transformation, by a transformation which corresponds to the thermal equilibrium of the fluid cavity with the external environment through the inflatable system. This balance is necessary following the modification of the internal temperature of the fluid cavity associated with the transformation linked to work. This thermal balance is slower to be implemented due to the thermal inertia of the inflatable system. In addition, the thermal balance is of smaller magnitude on the variation of volume of the fluid cavity than the transformation related to the work of the external force. As a result, it is possible to use sampling frequencies for the physical quantities, temperature and pressure, which are different. However, the same sampling frequency can also be used for both sensors. Preferably, the electronic device is fixed to the internal wall of the inflatable system. The inflatable system is in fact the most deformable element during the adiabatic transformation. And, since the temperature sensor is further away from the metal components, the relative temperature variations compared to the absolute temperature measured are greater because the thermal inertia of the wall of the inflatable system is less than that of the metal elements which have a greater inertia than that of the elastomer materials of the deformable walls. As a result, this improves the accuracy of temperature measurement and therefore the quality of the volume variation method.

[0009] In a first option, in the event that the sampling of the internal temperature recording is not sufficient to capture the first transformation, using the variation of the inflation pressure of the fluidic cavity, it is possible to determine the variation of the internal temperature of the fluid of the fluidic cavity which is determined, for this purpose, by the evolution law previously determined in the preliminary phase. It therefore converts the measurement of the internal pressure of the fluid of the fluidic cavity and an evaluation of the internal temperature of the fluid generated by the sole transformation linked to the work of the application of the external force.

[0010] In another first option, in case the sampling of the internal pressure recording is not sufficient to capture the first transformation, using the variation of the internal temperature of the fluidic cavity, it is possible to determine the variation of internal pressure of the fluid of the fluidic cavity which is determined, for this purpose, by the evolution law previously determined in the preliminary phase. It therefore converts the measurement of internal temperature of the fluid of the fluidic cavity and an evaluation of the internal pressure of the fluid generated by the only transformation linked to the work of the application of the external force.

[0011] Then, it is possible to evaluate an intermediate volume variation using a model of a fluid undergoing an adiabatic transformation. The term adiabatic is understood here to mean that the transformation that the fluid undergoes due to the application of the external force is carried out without heat exchange between the fluid cavity and the exterior of the inflatable system, which assumes that it is rapid. In any case, the recording of the internal pressure and especially of the internal temperature provides information on the thermal equilibrium between the fluid of the fluid cavity and the environment external to the inflatable system Therefore, by using the variation of the measured inflation pressure and the measured internal temperature variation of the fluid cavity, it is possible to estimate the variation in volume of the fluid cavity generated by the application of the external force, the fluid having undergone an adiabatic transformation. We will make the entirely suitable assumption for air or nitrogen that the fluid, in the gaseous state, of the cavity of the assembled equipped assembly is an ideal gas.

[0012] Preferably, it is possible to evaluate a first intermediate volume variation using a fluid model undergoing an adiabatic transformation. By focusing on the first transformation of the fluid linked to the work associated with the application of the external force. Therefore, by using the variation of the measured inflation pressure, by limiting oneself to the measurement points corresponding to the first transformation of the fluid, and to the internal temperature variation determined by using the evolution law defined in the preliminary phase, it is possible to estimate a first variation in volume of the fluidic cavity generated by the application of the external force, the fluid having undergone an adiabatic transformation. Of course, if the acquisition frequency of the internal pressure recording is not sufficient to accurately capture the first transformation of the fluid and the acquisition frequency of the internal temperature is higher, it is preferable to determine the internal pressure from the evolution law defined in the preliminary phase fed by the recording of the internal temperature, by limiting oneself to the measurement points corresponding to the first transformation of the fluid.

[0013] Preferably, a second intermediate volume variation is evaluated using a second transformation of the fluid. This second transformation is associated with the thermal equilibrium of the fluid with the external environment through the components of the inflatable system, mainly the deformable surface. The second volume variation undergone by the inflatable system following this second transformation is then evaluated using the variation in the internal temperature recorded in the fluid cavity during the transient phase linked to the application of the external force but subsequent to the transformation linked to the work of this external force. Taking into account this second volume variation guarantees better precision in the evaluation of the volume variation of the fluid cavity, which improves the precision of the measurement of the volume variation at the level of the inflatable system. However, the first intermediate volume variation is sufficient for the estimation, to a first order of magnitude, of the volume variation associated with the application of the external force. [0014] Of course, taking into account the variation in the external temperature of the inflatable system resulting from the thermal equilibrium of the assembled assembly also makes it possible to refine the measurement of the second variation in volume, generated by the application of the external force. However, in a simple approach, the inflatable system being preferably in a thermomechanically stable state, it is possible to take as the external temperature the initial internal temperature Tl of the fluid of the fluidic cavity of the inflatable system.

[0015] These two transformations can take place at each time increment or one after the other over a period of time measurements. These evaluations of the intermediate volume variation must be made with measurements during the transient period of loading of the vehicle until the establishment of the mechanical and possibly thermal equilibrium of the mounted assemblies of the vehicle. Once these equilibria are established, the temperature and pressure variations of the fluidic cavity are infinitesimal, they are then in a new thermomechanically stable state.

[0016] Optionally, once the intermediate volume variation has been evaluated for the inflatable system, it is appropriate to evaluate the associated static load variation resulting from the application of the external force on the inflatable system. To do this, it is appropriate to transform the volume variation of the inflatable system into an equivalent load variation. To this end, it is appropriate to take into account a characteristic of the inflatable system, in particular that of the deformable surface, which is called KSG which is the rigidity of the deformable surface of the inflatable system per unit volume. This quantity makes it possible to link the force applied by the inflatable system to the volume variation of the fluid cavity generated by the external force applied, the inflatable system being crushed on a surface which opposes the applied force. This characteristic can of course be a fixed quantity or obtained by an experimental characterization of the inflatable system or deduced from a numerical simulation campaign of the same inflatable system. The inflatable system must be in conditions of use close to those observed in the preliminary phase, that is to say around the internal temperature Tl and around the inflation pressure PL. Generally this rigidity of the inflatable system is a quantity defined locally around the initial point of use of the inflatable system in the reference associated with the internal pressure P, the internal temperature T and the volume of the fluid cavity V.

[0017] Advantageously, the extraction of the internal temperature variation T' ends when the recorded internal temperature T changes direction of variation or after a duration T0 corresponding to the end of the adiabatic transformation of the fluid. [0018] Advantageously, the extraction of the internal pressure variation P' ends when the recorded internal pressure P changes direction of variation or after a duration T0 corresponding to the end of the adiabatic transformation of the fluid.

[0019] Preferably, before the main step, the at least one equipped inflatable system is in a thermo-mechanically stabilized state.

[0020] It is preferable that the transient phenomena recorded at the level of the sensors of the electronic device are only due to the disturbance of the equilibrium of the inflatable system generated by the application of the external force. Thus, the other disturbances do not influence the response of the sensors, which improves the precision of the volume variation evaluated by the method. However, if the disturbance of the equilibrium of the inflatable system takes place on a different time scale than the disturbance associated with the application of the external force or if this disturbance results in lower amplitudes of the responses of the sensors of the electronic device, the method remains entirely relevant.

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

[0022] It is advantageous for the sensors measuring low-amplitude transient phenomena to be placed close to the appearance of these transient phenomena so as not to be drowned in the measurement noise. Thus, it is advantageous for the sensors to be located at the level of the deformable surface of the inflatable system. Finally, preferably, the sensors, mainly due to the temperature sensor, are positioned far away from the non-deformable elements, generally metallic, which have a greater thermal inertia than the deformable surface, conventionally made of elastomer material.

[0023] Advantageously, the temperature sensor operates with a resolution of less than one hundredth of a degree.

[0024] Advantageously, the temperature sensor operates with a resolution of less than one millibar.

[0025] Thus, it is possible to evaluate small volume variations and therefore small load variations. [0026] According to a particular embodiment, the determination of the initial volume V0 takes into account the geometry of the deformable surface of the inflatable system inflated to a reference pressure PO, preferably the reference pressure PO is the initial pressure PI.

[0027] Advantageously, the geometry of the deformable surface is determined using an identifier of the inflatable system, preferably obtaining the identifier of the inflatable system is carried out by a radiofrequency interrogation of an electronic device located in the inflatable system.

[0028] To initiate the measurement system and in particular the determination of the initial volume VI of the fluid cavity, it is appropriate to determine the volume V0 of the fluid cavity which corresponds to the volume delimited by the unloaded deformable surface, that is to say that the deformable surface is mounted on the inflatable system with a reference inflation pressure PO which is preferably the initial pressure PI.

[0029] To determine this volume V0, it is necessary to know the geometry of the fluid cavity of the unloaded inflatable system for a reference inflation pressure PO. This geometry can be accessible via a database of the inflatable system. Knowledge of the identity of the inflatable system makes it possible to isolate the correct geometry in this database. The identity of the inflatable system can be obtained through optical reading of markings affixed to the exterior of the inflatable system. The identity can also be transmitted by radiofrequency interrogation of an electronic device present on the inflatable system such as an RFID tag (acronym for Radio Frequency Identification) for example.

[0030] Preferably, the load Z of the inflatable system is estimated by a first relation according to the following formula:

Z = K _PP * P * A(F) = Kp _P * P * (Fl - F0)

[MATH1 ], where Kpp is the pneumatic stiffness of the deformable surface of the inflatable system per unit volume.

[0031] This is a simple and elementary model that relates the load applied to the inflatable system to the variation in volume of the fluid cavity between an unloaded state of volume V0 and a loaded state of volume VI, the inflation pressure P of the fluid cavity and the pneumatic rigidity of the inflatable system corresponding to the flattening of the inflatable system on a plane. Through this model, it is assumed that the rigidity of a structural nature of the inflatable system is negligible compared to that of a pneumatic nature, which is a realistic assumption for inflatable systems in general. However, it is entirely possible to take account for the structural stiffness in the previous formula by adding it to the product of the pneumatic stiffness and the inflation pressure.

[0032] According to an advantageous embodiment, the volume variation AV of the fluid cavity of the equipped inflatable system is estimated by solving the following differential equation:

[MATH 2], and with [MATH 3]

, where P is the internal pressure, V is the internal volume and T is the internal temperature of the fluid cavity.

[0033] This differential equation translates the link between the parameters of the fluid of the cavity of the inflatable system which are controlled on the one hand by an adiabatic transformation of the fluid and on the other hand by the fact that the fluid is a perfect gas.

[0034] The invention also relates to a use of the method for estimating the variation in volume AV of an inflatable system generated by the application of an external force to the stationary inflatable system in which the inflatable system is included in the group comprising a pneumatic envelope, a pneumatic shock absorber or a centralized system for inflating pneumatic envelopes.

[0035] These are cases of application of the method to industrial objects which are characterized by pneumatic rigidity and likely to be subjected to external forces.

[0036] The invention also relates to a method for evaluating the variation in load AZ applied to an inflatable system comprising the method for evaluating the variation in volume AV in which the method comprises a step of determining the variation in load AZ using a function F of which at least one parameter is the variation in volume AV of the fluid cavity of the inflatable system, preferably the function F is defined by a relation according to the following formula:

où KSG est la rigidité de la surface déformable du système gonflable par unité de volume. [0037] L’une des exploitations de la méthode est l’obtention de la variation de charge appliquée au système gonflable. A cet effet, il convient de prendre en compte une caractéristique du système gonflable, en particulier celle de la surface déformable, que l’on nomme rigidité de mise à plat par unité de volume KSG. Cette grandeur permet de relier la charge portée par le système gonflable à la variation de volume de la cavité fluidique générée par la charge portée, le système gonflable étant écrasé sur un sol perpendiculaire à la charge appliquée. Cette caractéristique peut bien entendu être une grandeur forfaitaire ou obtenue par une caractérisation expérimentale de système gonflable ou déduite d’une campagne de simulation numérique du même système gonflable. Le système gonflable doit être dans des conditions d’usage proches de celles observées en phase préliminaire, c’est-à-dire autour de la température interne Tl et autour de la pression de gonflage PL Généralement, cette rigidité de mise à plat du système gonflable est une grandeur définie localement autour du point d’usage initial du système gonflable dans le repère associé à la pression interne P, la température interne T et le volume de la cavité fluidique V. [MATH 4]

where KSG is the stiffness of the deformable surface of the inflatable system per unit volume. [0037] One of the uses of the method is to obtain the variation in load applied to the inflatable system. To this end, it is appropriate to take into account a characteristic of the inflatable system, in particular that of the deformable surface, which is called flattening rigidity per unit volume KSG. This quantity makes it possible to link the load carried by the inflatable system to the variation in volume of the fluid cavity generated by the load carried, the inflatable system being crushed on a ground perpendicular to the applied load. This characteristic can of course be a fixed quantity or obtained by an experimental characterization of the inflatable system or deduced from a numerical simulation campaign of the same inflatable system. The inflatable system must be in conditions of use close to those observed in the preliminary phase, that is to say around the internal temperature Tl and around the inflation pressure PL Generally, this flattening rigidity of the inflatable system is a quantity defined locally around the initial point of use of the inflatable system in the reference associated with the internal pressure P, the internal temperature T and the volume of the fluid cavity V.

Brief description of the drawings

[0038] The invention will be better understood on reading the following description, given solely as a non-limiting example and made with reference to the appended figures in which the same reference numbers designate identical parts throughout and in which:

• Fig. 1 presents a synopsis of the method for estimating the variation in AV volume of an inflatable system generated by the application of an external force according to the invention.

• Fig. 2 shows a temporal evolution of the internal temperature of the fluidic cavity at the outlet of the temperature sensor;

• Fig. 3 shows a temporal evolution of the internal pressure of the fluid cavity at the outlet of the pressure sensor;

• Fig. 4 presents a temporal estimate of the variation in volume of the fluidic cavity according to the invention;

• Fig. 5 shows a time estimate of the load variation of a mounted assembly of the vehicle associated with the trailer coupling to the vehicle. Detailed description of the embodiments

[0039] Fig. 1 shows a block diagram of the method for estimating the volume variation AV of an inflatable system generated by the application of an external force to the immobile inflatable system. This method comprises several phases.

[0040] The first is a preliminary phase which comprises at least actions 1 to 6 which follow one another through a continuous line link system. This preliminary phase which focuses on the inflatable system before the application of the external force obviously comprises the equipment of the inflatable system by the installation of a pressure sensor and a temperature sensor capable of measuring the pressure and the internal temperature of the fluid cavity delimited by the deformable surface by means of a dedicated electronic device. The first steps, noted 1 and 2, consist in determining the physical quantities of the fluid cavity of the inflatable system equipped with the measuring device such as the inflation pressure PI and the internal temperature TL. Preferably, these determinations can be made as a lump sum or through a specific measurement. The step noted 3 consists in determining the load carried ZI by the inflatable system equipped with the measuring device. This determination can be made as a lump sum or evaluated by a specific measurement. The step referenced 4 corresponds to obtaining specific quantities of the inflatable system equipped with a measuring device. One of these quantities is the volume V0 corresponds to the volume occupied by the fluid cavity of the inflatable system when the inflatable system is inflated to the pressure PI, strictly speaking, under the internal temperature Tl, but in the absence of any load carried, i.e. not resting on the ground for example. The second quantity is the flattening rigidity of the inflatable system per unit volume Kp, possibly dependent on the inflation pressure PI, the internal temperature Tl and the load carried ZI. Finally, a third set of quantities are those associated with the ideal gas behavior laws for the nature of the gas contained in the fluid cavity of the inflatable system. And the penultimate step of the preliminary phase, referenced 5, is a step of determining the occupied volume VI by the fluid cavity of the instrumented inflatable system subjected to the load ZI and under the inflation pressure PI and the temperature TL Finally the last step, noted 6, of the preliminary phase is the evaluation of the quantity of gas contained in the fluid cavity of the instrumented inflatable system by determining the number of moles of gas n present within the volume VL Here, the hypotheses associated with the ideal gas condition apply well, it is still necessary to identify the nature of the composition of the gas, that is to say a monatomic gas or a gas mixture. In addition, it is important, optionally, in this preliminary phase, although not represented, to determine the law of evolution linking the variation of internal pressure P to the variation of internal temperature T for the fluid of the fluidic cavity considered during an adiabatic transformation around the operating point of the inflatable system, that is to say the pressure PI, the temperature Tl and the load Zl.

[0041] Then we move on to the main step, the beginning of which corresponds to the application of the external force on the inflatable system. Necessarily, we record the temporal variations of the inflation pressure P(t) and the internal temperature T(t) of the inflatable system which are of the order of a millibar for the pressure sensor and a hundredth of a degree for the temperature sensor for uses of the tire type for passenger vehicles and trailers adapted to this type of vehicle. These recordings are then stored in a memory space to first filter the raw data using a low-pass filter to eliminate high-frequency phenomena, which corresponds to step referenced 11 for the pressure and step referenced 12 for the temperature.

[0042] Optionally, if the acquisition frequency of the internal temperature recording is not sufficient to capture the first transformation of the fluid, the temporal variation of the internal temperature T(t) of the fluid cavity is determined using the temporal variation of the internal pressure P(t) by using the evolution law determined in the preliminary step, which corresponds to step 12. And conversely, if it is the sampling frequency of the internal pressure recording p(t) which is not adapted to the capture of the first transformation of the fluid, the variation of the internal pressure is determined from the variation of the internal temperature using the evolution law linking the two quantities during an adiabatic transformation.

[0043] The connection system between optional steps and the steps essential to the process are illustrated with gray colored lines instead of being black. However, the connection systems of the main phase are illustrated by dotted lines, while those of the preliminary phase are solid lines. Finally, as will be seen later, the secondary phase has a connection system in the form of dashed lines.

[0044] One of the important steps of the main phase is the determination of the volume variation AV of the fluid cavity of the instrumented inflatable system through step 13. This corresponds to taking into account at least the transformation of the fluid of the fluid cavity linked to the work associated with the application of the external force. But also the second transformation of the fluid associated with the thermal equilibrium between the fluid of the fluid cavity and the exterior of the inflatable system. [0045] Using the variation of the internal pressure and the internal temperature, it is possible to feed a differential equation taking into account the previous hypotheses. The resolution by time increment of the differential equation makes it possible to obtain an estimate of the associated time variation of the volume of the fluidic cavity AV(t).

[0046] Optionally, another important step is the evaluation of the load variation carried AZ associated with the only volume variation previously evaluated AV which corresponds to step 14. For this, it is necessary to take into account again the flattening rigidity of the inflatable system, mainly that associated with the deformable surface, KSG per unit of volume.

[0047] Fig. 2 shows the temporal evolution of the temperature delivered by the temperature sensor of the electronic device arranged on an inflatable system, here a mounted assembly of a vehicle when a trailer is attached to the vehicle, thus suddenly applying an external force. The curve consisting of points 10 is the raw measurement of the temperature sensor while curve 11 corresponds to the temporal evolution of the filtered internal temperature, which is cleaned of high-frequency noise. It is this second curve which will then be used in the synoptic of figure 1.

[0048] This time recording of the internal temperature of the fluid cavity of the mounted assembly begins in the preliminary phase before the trailer is attached to the vehicle. The moment of attachment of the trailer corresponds to the abscissa of point 100 which marks the start of the main phase. A rapid drop in the internal temperature of the fluid cavity is then observed from this point 100 to point 101 where the drop in temperature stops and even increases to a lesser extent. This point 101 marks the transition between the work of the fluid associated with the attachment of the trailer which corresponds to a first transformation of the fluid which is similar to an adiabatic transformation linked to the work generated by the applied overload and then the heat exchange to the outside which corresponds to a second transformation of the fluid. The abscissa of this point 101 corresponds to the duration T0, taking the abscissa of point 100 as the origin of the times. Thus, the preliminary phase 50 ends at the abscissa of point 100. It precedes the main phase, which is separated into two successive phases. The first phase 51 is similar to an adiabatic transformation of the fluid corresponding to the work of the fluid following the attachment of the trailer to the vehicle. The second phase 52 corresponds to a thermal exchange of the fluid with the outside.

[0049] Fig. 3 shows the time evolution of the internal pressure of the fluid cavity for the same mounted assembly. Here, this time evolution is delivered by a pressure sensor of the electronic device arranged on a mounted assembly of the vehicle as illustrated by curve 12.

[0050] This change in the internal temperature 12 of the fluid cavity of the mounted assembly begins in the preliminary phase before the trailer is hitched to the vehicle. The moment of hitching corresponds to the abscissa of point 100 which marks the start of the main phase. From this point 100, a rapid drop in the internal pressure of the fluid cavity is then observed up to point 101 where the drop in pressure stops and then increases to a certain extent. This point 101 marks the transition between the work of the fluid associated with the hitching of the trailer which corresponds to a first transformation of the fluid which is similar to an adiabatic transformation and then the heat exchange towards the outside which corresponds to a second transformation of the fluid. The abscissa of this point 101 corresponds to the duration T0, taking the abscissa of point 100 as the origin of the times. Thus, the preliminary phase 50 ends at the abscissa of point 100. It precedes the main phase, which is separated into two successive phases. The first phase 51 is similar to an adiabatic transformation of the fluid corresponding to the work of the fluid following the attachment of the trailer to the vehicle. The second phase 52 corresponds to a thermal exchange of the fluid with the outside.

[0051] Fig. 4 shows the temporal evolution of the internal volume of the fluid cavity. Here, this temporal evolution, represented by the curve, is the output of the calculation of the volume variation by the proposed differential equation, also taking into account the thermal equilibrium with the external environment.

[0052] This evolution of the internal volume of the fluid cavity of the mounted assembly begins in the preliminary phase before the trailer is attached to the vehicle. The moment of attachment corresponds to the abscissa of point 100 which marks the start of the main phase. We then observe from this point 100 a rapid increase in the internal volume of the fluid cavity up to point 101 where the increase in the internal volume stops and then decreases to a certain extent. This point 101 marks the transition between the work of the fluid associated with the attachment of the trailer which corresponds to a first transformation of the fluid which is similar to an adiabatic transformation then the heat exchange towards the outside which corresponds to a second transformation of the fluid. The abscissa of this point 101 corresponds to the duration T0 by taking as the origin of the times the abscissa of the point 100. Thus, the preliminary phase 50 ends at the abscissa of the point 100. It precedes the main phase which is separated into two successive phases. The first phase 51 is similar to a transformation adiabatic of the fluid corresponding to the work of the fluid following the boarding of the passengers. The second phase 52 corresponds to a thermal exchange of the fluid with the exterior.

[0053] It is noted that at the end of phase 51, a good estimate of the variation in volume of the mounted assembly is obtained, which clearly shows that the work generated by the variation in load subjected to the mounted assembly occurs mainly during phase 51. The variations or oscillations observed correspond to the fluctuations of the transient phase corresponding to thermal equilibrium. As a result, the method described here produces a continuous measurement of the variation in the internal volume of the mounted assembly in the time domain.

[0054] Fig. 5 shows the time evolution of the load variation applied to the same mounted assembly equipped with the electronic device. Here, this time evolution, represented by curve 14, is the output of the calculation of the volume variation by the proposed differential equation taking into account the thermal equilibrium with the external environment which is multiplied by the flattening rigidity of the mounted assembly. Here, the rigidity taken is that which is locally identified at the level of the initial pressure of the mounted assembly, of the initial load applied to the mounted assembly and corresponding to the initial temperature. We could have taken into account the overall rigidity defined by the proposed formula which would already have given a good order of magnitude.

[0055] This evolution of the load 14 of the fluid cavity of the mounted assembly begins in the preliminary phase before the trailer is attached to the vehicle. The moment of attachment corresponds to the abscissa of point 100 which marks the start of the main phase. We then observe from this point 100 a rapid decrease in the load corresponding to a discharge in this case up to point 101 where the drop in the load stops and then decreases to a certain extent. This point 101 marks the transition between the work of the fluid associated with the attachment of the trailer which corresponds to a first transformation of the fluid which is similar to an adiabatic transformation then the heat exchange towards the outside which corresponds to a second transformation of the fluid. The abscissa of this point 101 corresponds to the duration T0 by taking as the origin of the times the abscissa of the point 100. Thus, the preliminary phase 50 ends at the abscissa of the point 100. It precedes the main phase which is separated into two successive phases. The first phase 51 is similar to an adiabatic transformation of the fluid corresponding to the work of the fluid following the attachment of the trailer. The second phase 52 corresponds to a thermal exchange of the fluid with the outside.

[0056] It is noted that at the end of phase 51, a good estimate of the variation in load applied to the assembled assembly is obtained, which clearly shows that the work generated by the load variation occurs mainly during phase 51. The observed variations or oscillations correspond to the fluctuations of the transient phase corresponding to thermal equilibrium. As a result, the method described here produces a continuous measurement of the temporal load variation of the mounted assembly in the time domain. Curve 80 corresponds to the measurement on a ground scale of the overload applied to the mounted assembly of the vehicle, which guarantees a reasonable estimate of the overload applied to the equipped mounted assembly. In conclusion, the applied load variation is well captured by the proposed method.

Claims

1. Method for estimating the variation in AV volume of an inflatable system generated by the application of an external force to the stationary inflatable system comprising the following steps: In the preliminary phase, - Equip the inflatable system with at least one temperature sensor, said sensor being capable of measuring the internal temperature of the fluid cavity of the inflation system delimited by at least one deformable surface of the inflatable system; - Equip the inflatable system with at least one pressure sensor, said sensor being capable of measuring the internal pressure of the fluid cavity of the inflation system; - Determine the initial load ZI exerted on the deformable surface of the inflatable system; - Determine the initial inflation pressure PI of the fluid cavity of the inflatable system; - Determine the initial internal temperature Tl of the fluid cavity of the inflatable system; - Evaluate the initial volume VI of the fluid cavity of the inflatable system using a first function comprising as parameter the volume VO of the fluid cavity of the unloaded inflatable system inflated to the initial pressure PI and the rigidity of the deformable surface of the inflatable system per unit volume Kp, - Evaluate the number of moles of fluid n in the fluid cavity of the inflatable system equipped from a model taking into account the inflation pressure PI, the initial volume VI, the temperature Tl; In the main phase: - Apply the external force on the deformable surface of the inflatable system; - Record the internal temperature T of the fluid cavity of the equipped inflatable system at an acquisition frequency Fl; - Record the internal pressure P of the fluid cavity of the equipped inflatable system at a frequency F2; and - Evaluate a variation in AV volume of the equipped inflatable system using the internal temperature T recorded and the internal pressure P recorded using a fluid model in adiabatic transformation, the fluid having ideal gas behavior. 2. Method for estimating the volume variation AV of an inflatable system generated by the application of an external force to the inflatable system when stationary according to claim 1, in which, in the preliminary phase, the method comprises a step of determining a law of evolution of the internal pressure P of the fluid cavity from the internal temperature T during an adiabatic transformation of the fluid of the fluid cavity of the inflatable system inflated and subjected to the load Zl, in the main phase, the method comprises a step of extracting the internal temperature variations T' generated by the sole adiabatic transformation of the fluid from the recording of the internal temperature T, the method comprises a step of determining an internal pressure P' of the fluid cavity of the inflatable system from the internal temperature T' and the law of evolution determined in the preliminary phase and the step of evaluating the volume variation AV of the inflatable system comprises a first phase where the evaluation is carried out with the extracted internal pressure P' and the determined internal temperature T' and at least one second phase where the evaluation is carried out with a part of the internal pressure P recorded outside a time frame corresponding to the extracted internal pressure variations P’ and a part of the recorded internal temperature T outside said time frame. 3. Method for estimating the volume variation AV of an inflatable system generated by the application of an external force to the inflatable system when stationary according to claim 1, in which, in the preliminary phase, the method comprises a step of determining a law of evolution of the internal temperature T of the fluid cavity from the internal pressure P during an adiabatic transformation of the fluid of the fluid cavity of the inflatable system inflated and subjected to the load Zl, in the main phase, the method comprises a step of extracting the internal pressure variations P' generated by the sole adiabatic transformation of the fluid from the recording of the internal pressure P, the method comprises a step of determining an internal temperature T' of the fluid cavity of the inflatable system from the internal pressure P' and the law of evolution determined in the preliminary phase and the step of evaluating the volume variation AV of the inflatable system comprises a first phase where the evaluation is carried out with the extracted internal temperature T' and the determined internal pressure P' and at least one second phase where the evaluation is carried out with part of the internal temperature T recorded outside a time frame of the extracted internal temperature variations T' and part of the recorded internal pressure P outside said time frame. 4. Method for estimating the variation in volume AV of an inflatable system generated by the application of an external force on the inflatable system when stationary according to claim 2, in which the extraction of the variation in internal temperature T' ends when the recorded internal temperature T changes direction of variation or after a duration TO corresponding to the end of the adiabatic transformation of the fluid. 5. Method for estimating the variation in volume AV of an inflatable system generated by the application of an external force to the inflatable system when stationary according to claim 3, in which the extraction of the variation in internal pressure P' ends when the recorded internal pressure P changes direction of variation or after a duration TO corresponding to the end of the adiabatic transformation of the fluid. 6. Method for estimating the variation in AV volume of an inflatable system generated by the application of an external force to the inflatable system when stationary according to one of claims 1 to 5 in which, before the main step, the equipped inflatable system is in a thermomechanically stabilized state. 7. Method for estimating the variation in volume AV of an inflatable system generated by the application of an external force on the inflatable system when stationary according to one of claims 1 to 6, in which the temperature sensor and the pressure sensor are placed in a subspace of the closed fluid cavity delimited by the deformable surface of the inflation system. 8. Method for estimating the variation in AV volume of an inflatable system generated by the application of an external force to the inflatable system when stationary according to one of claims 1 to 7, in which the temperature sensor operates with a resolution of less than one hundredth of a degree. 9. Method for estimating the variation in AV volume of an inflatable system generated by the application of an external force to the inflatable system when stationary according to one of the Claims 1 to 8 wherein the pressure sensor operates with a resolution of less than a millibar. 10. Method for estimating the variation in volume AV of an inflatable system generated by the application of an external force to the inflatable system when stationary according to one of claims 1 to 9, in which the determination of the initial volume V0 takes into account the geometry of the deformable surface of the inflatable system inflated to a reference pressure PO, preferably the reference pressure PO is the initial pressure PI. 11. Method for estimating the variation in AV volume of an inflatable system generated by the application of an external force to the inflatable system when stationary according to claim 10 in which the geometry of the deformable surface is determined using an identifier of the inflatable system, preferably obtaining the identifier of the inflatable system is carried out by a radiofrequency interrogation of an electronic device located in the inflatable system. 12. Method for estimating the variation in volume AV of an inflatable system generated by the application of an external force on the inflatable system when stationary according to one of claims 1 to 11 in which the load Z of the equipped inflatable system is estimated by a relationship according to the following formula: Z = K _PP * P * A(F) = Kp _P * P * (Fl - FO) [MATH1] where Kpp is the pneumatic stiffness of the deformable surface of the inflatable system per unit volume. 13. Method for estimating the volume variation AV of an inflatable system generated by the application of an external force on the inflatable system when stationary according to one of claims 1 to 12 in which the volume variation AVl of the fluid cavity of the equipped inflatable system is estimated by solving the following differential equation:

[MATH 2], and with [MATH 3]

, where P is the internal pressure, V is the internal volume and T is the internal temperature of the fluid cavity. 14. Method for evaluating the variation in load AZ applied to an inflatable system comprising the method for evaluating the variation in volume AV according to one of claims 1 to 13 in which the method comprises a step of determining the variation in load AZ using a function F of which at least one parameter is the variation in volume AV of the fluid cavity of the inflatable system, preferably the function F is defined by a relation according to the following formula: [MATH4]

where KSG is the stiffness of the deformable surface of the inflatable system per unit volume.