Method and system for determining the level of a liquid in a container and / or conduit, in particular fuel in an aircraft tank

Abstract

Method and system for determining the level of a liquid in a container and / or conduit, in particular fuel in an aircraft tank. One aspect of the invention relates to a method for determining the level of a liquid in a container and / or conduit (1), for example a tank, comprising at least a first and a second sensor (11) positioned respectively above and below the liquid level (5), the liquid level being determined from the propagation speeds of a first and a second propagation mode and a propagation time of a guided elastic wave propagating in the wall of the container or conduit according to the first mode above the liquid level (5) and according to the second mode below the liquid level (5). Figure to be published with the abstract: Figure 1

Description

Title of the invention: Method and system for determining the level of a liquid in a container and / or conduit, in particular fuel in an aircraft tank. TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention is that of measuring the level and / or mass of a liquid in a container and / or conduit, in particular fuel carried in an aircraft tank.

[0002] The present invention relates to a method and system of ultrasonic gauging for determining a level and / or mass of liquid in a container and / or conduit, in particular fuel in an aircraft tank. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] In aeronautics, the mass of fuel carried in a tank is essential safety information for the pilot, in particular to know the flight range of the aircraft, and for balancing the mass of the aircraft by compensating the center of gravity with respect to the center of thrust.

[0004] Existing fuel gauging systems rely on complex measurement technologies using sensors installed inside the tank. Since such measurement systems require a power supply to the tank, for example in electrical or optical form, they are subject to stringent requirements and standards, designated by the acronym ATEX, for Explosive Atmosphere, for installation and maintenance, in order to be compatible with use in such an atmosphere while being resistant to chemical attack.

[0005] Most fuel gauging systems comprise at least two separate measuring modules: • One to measure high and low point fuel levels, indicating that the filler valves should be closed (high level) or warning the pilot that a fuel reserve is being reached (low level); and • The other to estimate a mass of fuel on board from two different devices, measuring respectively a density and a fuel level, the mass of fuel being deduced from a height / volume law knowing the geometry of the tank and the attitude of the aircraft (yaw, pitch, roll, etc.).

[0006] Regarding the measurement of point levels, the most common technologies rely on intrusive technologies such as a float, a self-heating thermistor or a capacitive sensor.

[0007] Various devices for measuring the density of fuel exist, such as a densimeter, an immersed float possibly associated with a counterweight, a mechanical oscillator or an immersed plate capacitor based on the Clausius-Mossotti law.

[0008] The most common technology for measuring fuel level in the tank uses capacitive sensors immersed in the fuel. There are also approaches using guided waves along a waveguide immersed in the fuel, for example for electromagnetic or ultrasonic waves.

[0009] Some approaches propose a non-intrusive measurement of the fuel level, notably using volume or guided ultrasonic waves. The drawback of the volume ultrasonic wave approach is that it is necessary to be able to capture the wave after reflection at the fuel / gas interface. Since the liquid is rarely at rest in the tank, Fonde is diffracted rather than reflected specularly, which makes the backscattered wave difficult for the sensor to detect due to its low energy.

[0010] The guided ultrasonic wave approach overcomes this drawback but does not allow taking into account the influence of temperature on the error in estimating its level, unless the properties of the fuel are known.

[0011] A guided ultrasonic wave approach exploits the conversion of an antisymmetric Lamb mode Ao into a Quasi-Scholte (QS) mode during its propagation through the tank wall (Lingyu Yu and Zhenhua Tian, ​​Case study of guided wave propagation in a one-side water-immersed steel plate, Case Studies in Nondestructive Testing and Evaluation, vol. 3, p. 1-8, 2015). It is shown that the amplitude and time of flight of the wave vary with the fuel level, due to the conversion, thus providing a much more precise and robust measurement of the fuel level. However, no solution is proposed to improve the robustness of the measurement with respect to environmental conditions, particularly temperature. Consequently, at a given temperature, the level measurement as presented in this approach is relative.In other words, the fuel level is measured relative to two level measurements, but not absolutely with respect to the dimensions of the tank.

[0012] In practice, knowing the temperature, for example through a thermocouple, is not sufficient. This necessitates very precise temperature measurements at various points within the tank, as thermal equilibrium is generally not reached during aircraft operation. This implies having a large number of temperature measurement points.

[0013] At a minimum, a temperature measurement is required at the fuel level and another at the gas level in the tank. Knowledge of the temperature therefore requires additional instrumentation, and a fusion of two technologies within the same system, which increases installation and maintenance constraints as well as the probability of system failure.

[0014] Therefore, there is a need for a simplified system for determining the level and / or mass of liquid in a container and / or conduit, robust to experimental conditions and compatible with the instrumentation constraints on an aircraft. Summary of the invention

[0015] The invention offers a solution to the problems mentioned above, by proposing a method and a system allowing the measurement of the different quantities necessary for determining the level of a liquid in a container and / or a conduit from a single set of sensors.

[0016] A first aspect of the invention relates to a method for determining the level of a liquid in a container and / or conduit, the container and / or conduit comprising: • a wall, in particular with an inner face and an outer face, the wall delimiting an internal volume of the container and / or conduit containing the liquid, and • a plurality of ultrasonic sensors comprising at least one first sensor positioned above the liquid level and at least one second sensor positioned below the liquid level, the liquid level in the container and / or conduit being determined from: • The propagation speed of a first propagation mode determined by the propagation of a guided wave in the wall above the liquid level and captured by the first sensor; • The propagation speed of a second propagation mode determined by the propagation of a guided wave in the wall below the liquid level and captured by the second sensor; and • The propagation time of a guided wave generated by the first and / or second sensor propagating in the wall according to the first mode of propagation above the liquid level and according to the second mode of propagation below the liquid level.

[0017] Thanks to the invention, it is possible to determine a liquid height taking into account the environmental conditions in which the container and / or the conduit which contains it is located.

[0018] Indeed, the method allows for self-calibration of the sensors for measuring the liquid level, thus eliminating the influence of experimental conditions. mental factors, including those related to temperature. The level is therefore estimated robustly under these experimental conditions.

[0019] The method is also simple to implement since it only requires the emission of ultrasonic waves, particularly in the wall. Furthermore, it is advantageous to implement the method by generating a single guided ultrasonic wave, for example by the first sensor, to simultaneously determine the propagation velocities of the first and second modes and the liquid level in the container and / or conduit.

[0020] Furthermore, the method does not require multiple measuring instruments to perform the measurements. Indeed, a system comprising only ultrasonic sensors is sufficient to determine the various quantities involved. Therefore, for example, it is not necessary to add temperature sensors to the tank to compensate for the effect of temperature on the propagation of guided waves.

[0021] Most importantly, the method does not require any intrusive measures to be implemented. The method is therefore compatible with application under ATEX regulations and poses no risk of chemical attack to the sensors due to the nature of the liquid, particularly in the case of a fuel.

[0022] The method therefore allows for rapid instrumentation in preparation and installation time, with low maintenance costs.

[0023] Since any ultrasonic sensor technology can be used without detracting from the advantages of the method, it is possible to use compact and simple-to-instrument sensor technologies, facilitating access to acquisition systems and sensors for maintenance.

[0024] Finally, the method is compatible for any type of container and / or conduit and any application subject to ATEX type instrumentation constraints and / or chemical attack.

[0025] The method is therefore compatible for any aeronautical application, in particular during flight, including for semi-rigid or flexible tanks such as those carried in a helicopter.

[0026] Other applications of the method are possible, such as in the automotive, naval or storage sectors, for example for drinking water, chemicals, food products, etc. Although described here for liquids (of different physico-chemical natures: viscosity, density, etc.), the proposed approach is also compatible for powdered or granular compounds.

[0027] In addition to the characteristics just mentioned in the preceding paragraph, the method according to the first aspect of the invention may have one or more complementary characteristics from among the following, considered individually or according to all technically possible combinations.

[0028] In one embodiment, the liquid is a fuel.

[0029] In one embodiment: • The first propagation mode is the antisymmetric mode Ao of a guided Lamb wave; • The second mode of propagation is the Quasi-Scholte mode of a guided elastic wave.

[0030] The determination of the liquid level therefore relies on the propagation of guided modes, which are simple to generate and do not require any specific instrumentation other than an ultrasonic sensor generating guided waves. Furthermore, the Ao mode, converting into the Quasi-Scholte mode, is sensitive to the presence of liquid, thus enabling the accuracy of the liquid level calculation.

[0031] In one embodiment: • The propagation speed of the first propagation mode is estimated by generation and then capture of a wave guided by the first sensor after reflection on a first reflector located on the wall, in particular the inner face, and above the liquid level, such that y _ 2 / îi. where h] is the distance between the first sensor and the first reflector and f] is the round-trip propagation time of the first propagation mode between the first sensor and the first reflector; • The propagation speed VQS of the second propagation mode is estimated by generating and then capturing a wave guided by the second sensor after reflection on a second reflector located on the wall, specifically the inner face, and below the liquid level, such that y_ where h2 is the distance between the second sensor and the second reflector and is the round-trip propagation time of the second propagation mode between the second sensor and the second reflector; and • The height H of the liquid level relative to the second sensor is determined by where ^12 is the propagation time of H - = Ves - 2ht Guided stream propagating between the first and second sensors according to the first propagation mode above the liquid level and according to the second propagation mode below the liquid level, and L2 is the distance between the first sensor and the second sensor.

[0032] In one embodiment, the first reflector is at least a part of the upper surface of the container and / or conduit and / or the second reflector is at least a part of the lower surface of the container and / or conduit.

[0033] In one embodiment, the plurality of sensors further comprises a a third sensor positioned below the liquid level and a fourth sensor positioned above the liquid level, the first and fourth sensors being po positioned at roughly the same height, and the second and third sensors being positioned at approximately the same height, and in which: • The propagation speed ^40 of the first propagation mode is estimated by capturing a guided wave transmitted between the first and fourth sensors, such as y, where AJ4 is the distance between the first and fourth sensors, and ^4 is the propagation time of the first mode of Guided foundation transmitted to cover the distance ij4; The propagation speed ^5 of the second propagation mode is estimated by capturing a guided wave transmitted between the second and third sensors, such as y _ where ^23 is the distance between the second and third sensors, and ^23 is the propagation time of the second mode of Guided foundation transmitted to cover the distance ^23; and The height H of the liquid level relative to the second sensor is determined by q2 - , where fj 2 is the propagation time of guided foundation propagating between the first and second sensors according to the first mode of propagation above the liquid level and according to the second mode of propagation below the liquid level, and is the distance between the first sensor and the second sensor.

[0034] Thanks to these embodiments, determining the liquid height to take into account the experimental conditions is simple and quick to implement.

[0035] In one embodiment, the method further comprises: • Determination of the liquid's density from: • An estimate of the wall temperature; • A propagation speed of the second propagation mode; and • A dispersion curve of the second propagation mode; or • A measurement of the electrical impedance of one of the sensors of the plurality of sensors, said sensor being positioned below the liquid level; • Determining the mass of liquid from the density of the liquid and the level of the liquid.

[0036] It is thus possible to determine the mass of fuel on board from the level measurement carried out, without adding or modifying the instrumentation of the sensors on the container and / or conduit.

[0037] In one embodiment, the wall temperature is estimated by means of a guided wave generated by one of the first or second sensors and captured by the other of the first or second sensors and propagating in the wall according to a third mode of propagation.

[0038] In one embodiment, the temperature of the wall is estimated by inverting a dispersion curve of a third propagation mode as a function of the propagation speed of said third propagation mode in the wall.

[0039] In one embodiment, the third propagation mode is the symmetric mode So of a guided Lamb wave.

[0040] In one embodiment, the wall temperature is estimated by means of a measurement via a temperature sensor, in particular a thermocouple, which can be positioned outside the container and / or conduit, in particular on the external face.

[0041] In one embodiment, the density of the liquid is determined via estimation of the propagation speed of the second propagation mode in the wall and by inversion of the dispersion curve of the second propagation mode for the estimated wall temperature.

[0042] In one embodiment, the first propagation mode and / or the second propagation mode are generated by means of a broadband excitation signal.

[0043] In one embodiment, the third propagation mode is generated by means of a broadband excitation signal.

[0044] The advantage of generating the guided wave using the broadband excitation signal is to excite the first, second, and third propagation modes over a controlled frequency range. This makes it possible to determine the propagation time of each mode by averaging the measured propagation times for each frequency of each mode, thus improving the accuracy of the propagation time estimation.

[0045] In one embodiment, the method includes a preliminary step of determining the wall thickness by calibration with a known fluid or by direct measurement.

[0046] In one embodiment, the plurality of sensors further includes an intermediate sensor disposed at a distance from the wall or on the wall, in particular on the external face, and positioned between the first and second sensors, and the method includes determining a gradient of the propagation speed of the first and / or second propagation modes from the propagation time of the first and / or second propagation modes, respectively, by means of the intermediate sensor.

[0047] In one embodiment, the method includes determining a gradient of the propagation speed of the third propagation mode from the propagation time of the third propagation mode by means of the intermediate sensor.

[0048] It is thus possible to take into account the inhomogeneity of the liquid's properties, in particular its density which can vary with the depth in the container and / or conduit.

[0049] A second aspect of the invention relates to a system for determining a liquid level in a container and / or conduit, the container and / or conduit comprising a wall with an inner face and an outer face, the inner face of the wall delimiting an internal volume of the container and / or conduit containing the liquid, the system comprising: • A plurality of ultrasonic sensors positioned at a distance from the wall and / or on the wall, including: • A first sensor, positioned above the liquid level; and • A second sensor, positioned below the liquid level; • An acquisition module connected to the plurality of ultrasonic sensors and configured to drive the plurality of ultrasonic sensors so as to generate a guided wave and / or acquire samples of a guided wave captured by one of the sensors in the plurality of ultrasonic sensors; and • A processing module connected to the acquisition module and configured to implement the method according to the first aspect from the acquired samples.

[0050] Thanks to this second aspect, the system for determining the liquid level is simple and quick to instrument on the container and / or conduit to implement the method according to the first aspect of the invention.

[0051] A third aspect of the invention relates to a computer program product comprising instructions which, when the program is executed on a computer, lead the latter to implement the steps of the method according to the first aspect.

[0052] A fourth aspect of the invention relates to a computer-readable recording medium comprising instructions which, when executed by a computer, lead the computer to implement the steps of the method according to the first aspect.

[0053] A fifth aspect of the invention relates to a method for determining the mass of a liquid in a container and / or conduit comprising: • a wall, in particular with an inner face and an outer face, the wall delimiting an internal volume of the container and / or conduit containing the liquid, and • at least one ultrasonic sensor positioned at a distance from the wall and / or on the wall, the mass of the liquid in the container and / or conduit being determined from the density of the liquid and the level of the liquid in the container and / or conduit, the density being determined from: • An estimate of the wall temperature; • The propagation speed of a second propagation mode determined by the propagation of a guided wave in the wall below the liquid level and captured by the sensor; and • A dispersion curve of the second propagation mode.

[0054] Furthermore, by using sensors arranged outside the container and / or conduit, it may be possible to determine a mass of liquid contained in a container and / or conduit in a non-intrusive manner because the method then relies on non-intrusive sensor technologies.

[0055] The method is therefore compatible with an application under ATEX regulations and without risk of chemical attack for the sensors due to the nature of the liquid, in particular when it is a fuel.

[0056] The method therefore allows for rapid instrumentation in terms of preparation and installation time, with low maintenance costs.

[0057] The method is also simple to implement since it only requires the emission of ultrasonic waves into the wall. Furthermore, it is advantageously possible to implement the method by generating a single guided ultrasonic wave, for example via a first sensor, to determine both the temperature of the wall and the density of the liquid.

[0058] Furthermore, the method does not require multiple measuring instruments to perform the measurements. Indeed, a system comprising only ultrasonic sensors is sufficient to determine the various quantities involved. Therefore, for example, it is not necessary to add temperature sensors to the tank to compensate for the effect of temperature on the propagation of guided waves.

[0059] Since any ultrasonic sensor technology can be used without detracting from the advantages of the method, it is possible to use compact and simple-to-instrument sensor technologies, facilitating access to acquisition systems and sensors for maintenance.

[0060] Finally, the method is compatible for any type of container and / or conduit and any application subject to ATEX type instrumentation constraints and / or chemical attack.

[0061] The method is therefore compatible for any aeronautical application, in particular during flight, including for semi-rigid or flexible tanks such as those carried in a helicopter.

[0062] Other applications of the method are possible, such as in the automotive, naval, or storage sectors, for example for drinking water, chemicals, food products, etc. Although described here for liquids (of different physicochemical properties: viscosity, density, etc.), the proposed approach is also compatible with powdered or granular compounds.

[0063] In addition to the characteristics just mentioned in the preceding paragraph, the method according to the fifth aspect of the invention may have one or more complementary characteristics from among the following, considered individually or according to all technically possible combinations.

[0064] In one embodiment, the liquid is a fuel.

[0065] In one embodiment, the second propagation mode is the Quasi- mode Scholte of a guided elastic wave.

[0066] The determination of the liquid mass relies on the propagation of a guided mode that is simple to generate and does not require specific instrumentation other than an ultrasonic sensor generating guided waves. Furthermore, the Quasi-Scholte mode is sensitive to the presence of liquid, thus improving the accuracy of the density calculation.

[0067] In one embodiment, the method according to the fifth aspect comprises at least one first sensor and at least one second sensor, and wherein the temperature of the wall is estimated by means of a guided wave generated by the first, respectively the second, sensor and captured by the second, respectively the first, sensor and propagating in the wall according to a third mode of propagation.

[0068] In one embodiment, the third propagation mode is the symmetric mode So of a guided Lamb wave.

[0069] In one embodiment, the temperature of the wall is estimated by inverting a dispersion curve of the third propagation mode as a function of the propagation speed of said third propagation mode in the wall.

[0070] It is thus possible to determine the wall temperature quickly and easily without using any equipment other than the two sensors mentioned. Therefore, it is not necessary to add any additional equipment to measure this temperature.

[0071] Furthermore, the determination of the wall temperature relies on the propagation of a guided mode that is simple to generate and does not require any specific instrumentation other than an ultrasonic sensor generating guided waves. Moreover, the So mode is relatively insensitive to the presence of liquid in the container and / or conduit, allowing for accurate temperature measurement.

[0072] In one embodiment, the temperature of the wall is estimated by means of a measurement via a temperature sensor, for example a thermocouple, in particular positioned outside the container and / or conduit, on the wall.

[0073] It is therefore alternatively possible to use another measuring instrument to evaluate the temperature of the wall.

[0074] In one embodiment, the density of the liquid is determined via the estimation of the propagation speed of the second propagation mode in the wall and by inversion of the dispersion curve of the second propagation mode for the estimated wall temperature.

[0075] In one embodiment, the method comprises at least one first sensor positioned above the liquid level and at least one second sensor positioned below the liquid level, and wherein the liquid level is determined from: • The propagation speed VA0 of a first propagation mode is estimated by generating and then capturing a wave guided by the first sensor after reflection on a first reflector located on the inner face and above the liquid level, such that , where is the distance between the first sensor and first reflector and is the round-trip propagation time of the first propagation mode between the first sensor and the first reflector • The propagation speed Vqs of the second propagation mode is estimated by generation and then capture of a wave guided by the second sensor after reflection on a second reflector located on the inner face and below the liquid level, such as y _ 2hi where h2 is the distance between the second sensor and the second reflector and is the round-trip propagation time of the second propagation mode between the second sensor and the second reflector; The height H of the liquid level relative to the second sensor is determined by try - y- - ÿr,, where / 12 is the propagation time of guided Fonde se propagating between the first and second sensors according to the first propagation mode above the liquid level and according to the second propagation mode below the liquid level, and Ll2 is the distance between the first sensor and the second sensor.

[0076] In one embodiment, the first reflector is at least a part of the upper surface of the container and / or conduit and / or the second reflector is at least a part of the lower surface of the container and / or conduit.

[0077] In one embodiment, the method according to the fifth aspect comprises at least a first sensor, a second sensor, a third sensor and a fourth sensor, the first and fourth sensors being positioned above the liquid level, in particular at approximately the same height, and the second and third sensors being positioned below the liquid level, in particular at substantially the same height, and in which the liquid level is determined from: • The propagation speed VA0 of the first propagation mode is estimated by capturing a guided wave transmitted between the first and fourth sensors, such that y = —, °where ^14 is the distance between the first and fourth sensors, and / ¼ is the propagation time of the first mode of guided wave transmitted to travel the distance ^14; • The propagation speed Vqs of the second propagation mode is estimated by capturing a guided wave transmitted between the second and third sensors, such that _ ^23, where is the distance between the second and third sensors, and L3 is the propagation time of the second mode of guided flux transmitted to travel the distance The height H of the liquid level relative to the second sensor is determined by L^xy-L^x / ^ ' °ù ^12 is the propagation time of guided Fonde se propagating between the first and second sensors according to the first propagation mode above the liquid level and according to the second propagation mode below the liquid level, and Li2 is the distance between the first sensor and the second sensor.

[0078] In one embodiment, the method according to the fifth aspect comprises at least one first sensor and at least one second sensor, the first sensor and the second sensor being positioned in particular at substantially the same height, and wherein the liquid level is a determined point level such that: • The liquid level is above or at the same height as the first and second sensors when a wave emitted by the first and / or second sensors and captured by the second and / or first sensors, respectively, propagates according to the second mode of propagation; • The liquid level is below the height of the first and second sensors when a wave emitted by the first and / or second sensors and captured by the second and / or first sensors, respectively, propagates according to the first mode of propagation.

[0079] Thanks to these embodiments, determining the liquid height to take into account the experimental conditions is simple and quick to implement. Furthermore, it is not necessary to add additional measuring instruments since the ultrasonic sensors are sufficient on their own to measure and determine all the data necessary for calculating the liquid level in the container and / or conduit.

[0080] In one embodiment, the first propagation mode, the second mode of propagation and / or the third mode of propagation are generated by means of a broadband excitation signal.

[0081] The advantage of generating the guided wave using the broadband excitation signal is to excite the first, second, and third propagation modes over a controlled frequency range. This makes it possible to determine the propagation time of each mode by averaging the propagation times measured for each frequency of each mode, thus improving the accuracy of the propagation time estimation.

[0082] In one embodiment, the method further includes a preliminary step of determining the wall thickness by calibration with a known fluid or by direct measurement.

[0083] In one embodiment, the method according to the fifth aspect further includes an intermediate sensor disposed at a distance from the wall or on the wall, and positioned between the first and second sensors, and the method includes determining a gradient of the propagation speed of the first, second and / or third propagation modes from the propagation time of said first, second and / or third propagation modes by means of the intermediate sensor.

[0084] It is thus possible to take into account the inhomogeneity of the properties of the liquid, in particular its density which can vary with the depth in the container and / or conduit.

[0085] A sixth aspect of the invention relates to a system for determining a mass of liquid in a container and / or a conduit, the container and / or conduit comprising a wall with an inner face and an outer face, the wall delimiting an internal volume of the container and / or conduit containing the liquid, the system comprising: • At least one ultrasonic sensor disposed at a distance from the wall and / or on the wall; • An acquisition module connected to the ultrasonic sensor and configured to drive the ultrasonic sensor to generate a guided wave and / or acquire samples of a guided wave captured by the ultrasonic sensor; and • A processing module connected to the acquisition module and configured to implement the method according to the fifth aspect from the acquired samples.

[0086] Thanks to this sixth aspect, the gauging system is simple and quick to instrument on the container and / or conduit to implement the method according to the fifth aspect of the invention.

[0087] A seventh aspect of the invention relates to a computer program product comprising instructions which, when the program is executed on a computer, lead him to implement the steps of the method according to the fifth aspect.

[0088] An eighth aspect of the invention relates to a computer-readable recording medium comprising instructions which, when executed by a computer, lead the computer to carry out the steps of the method according to the fifth aspect.

[0089] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES

[0090] The figures and examples described are presented as an illustration and in no way limit the invention. • Fig. 1 shows a schematic representation of the gauging system according to the invention implemented on a tank containing fuel, according to one embodiment. • Fig. 2 is a synoptic diagram illustrating the sequence of steps of a gauging method according to the invention, according to one embodiment. • Fig. 3 is a schematic representation of the container and / or conduit according to [Fig.1] detailing the physical quantities used by the method according to [Fig.2] according to a first embodiment. • Fig. 4 is a schematic representation of the container and / or conduit according to Fig. 1, detailing the physical quantities used by the method according to Fig. 2 in a second embodiment. • Figure 5 is a schematic representation of one embodiment of the instrumentation of the container and / or conduit. • Figure 6 is a set of experimental signals acquired using the system according to [Fig.1], according to one embodiment. • Fig. 7 illustrates the variations in the propagation speed of a guided wave following the So mode in an aluminum plate, as a function of temperature variations. • Fig. 8 is a schematic representation of the positioning of sensors to determine a point level in a container and / or conduit, according to one embodiment. • The [Fig.9] is a schematic representation of the propagation of a guided wave in the wall of a container and / or a conduit, according to one embodiment. DETAILED DESCRIPTION

[0091] Unless otherwise specified, the same element appearing on different figures presents a unique reference.

[0092] The invention relates to an ultrasonic gauging method and system for determining the level and / or mass of liquid in a container and / or conduit. The application proposed below concerns an aircraft tank. However, the invention can be used for any other container and / or conduit containing a liquid in an environment subject to instrumentation constraints and safety requirements, particularly those related to explosive atmospheres (ATEX) and risks of chemical attack.

[0093] The invention is based on the generation of guided ultrasonic waves in the wall of the container and / or conduit, here the tank, to determine the level and density of the liquid, here the fuel, in the tank, in order to deduce the mass of liquid carried. In particular, three modes of guided waves are excited: the antisymmetric mode Ao of a Lamb wave, the symmetric mode So of a Lamb wave, and the Quasi-Scholte mode.

[0094] Figure 1 illustrates the gauging system 10 implemented on a container and / or conduit 1, the container and / or conduit here being a tank 1.

[0095] The tank 1 comprises a wall 2, which includes an inner face 2i and an outer face 2e. The wall, in particular its inner face 2i, delimits an internal volume of the container and / or conduit 1. The internal volume contains the liquid. The inner face 2i is therefore in contact with the liquid. The outer face 2e is exposed to the surrounding environment in which the container and / or conduit 1 is located. In the first embodiment presented, the tank 1 is carried on board an aircraft, such as an airplane or a helicopter, and the tank 1 is located in a storage space dedicated to said tank 1.

[0096] The reservoir 1 also includes an upper surface 3 and a lower surface 4. The internal volume is therefore also delimited by the upper surface 3 and lower surface 4.

[0097] The tank 1 may also include other elements, such as equipment for circulating fuel to the engine to supply it, such as a pump device and a connecting circuit, and equipment for conveying fuel into the tank for storage, such as a supply circuit.

[0098] The term "liquid level" means the height of the interface formed by the upper surface of the liquid with a gas in the container and / or conduit 1 relative to a fixed reference point such as the lower surface 4. The dimension of the liquid level 5 is preferably a distance, for example in millimeters, centimeters, meters, etc. The liquid level 5 thus delimits an upper part 1a and a lower part 1b in said container and / or conduit 1 such that the lower part 1b corresponds to the portion of the container and / or conduit where the liquid is located, and the upper part corresponds to the part of the container and / or conduit where the gas is located. The gas is a chemical compound mainly composed, for example, of fuel vapors and air or nitrogen-enriched air.

[0099] The wall then comprises an upper section 2a and a lower section 2b, corresponding to the upper part 1a and the lower part 1b, respectively, of the container and / or conduit 1.

[0100] The geometry and dimensions of the container and / or conduit 1 are predefined. That is to say, the geometry and dimensions of the internal volume, the upper surface 3, the lower surface 4, and the wall 2 are predefined. In some embodiments, the wall thickness is not predefined and must be determined.

[0101] A characteristic is "predefined" if it is perfectly known at the time the method is implemented and is not a characteristic for which a determination must be made. In particular, the properties of the container and / or conduit and its components are predefined since they are the subject of a controlled design and manufacturing process. The characteristics and positions of the components of the gauging system are also predefined because they are controlled and known to the operator.

[0102] The gauging system 10 comprises a plurality of ultrasonic sensors 11, an acquisition module 12 and a processing module 13.

[0103] The plurality of ultrasonic sensors 11 can be arranged on the wall 2, in particular on the external face 2e of the wall 2. In other words, each sensor 11 of the plurality of sensors 11 is positioned on the container and / or conduit 1, in contact with the wall 2. The gauging of the liquid is therefore carried out in a non-intrusive manner.

[0104] In certain alternatives, depending on the sensor technology used and the intended application, the sensors 11 may be non-contact sensors. "Non-contact" refers to sensor technologies that generate an ultrasonic wave in a room without requiring contact between the source and the room for the generation of the sound. For example, this could involve a sensor technology very close to the wall (such as electromagnetic acoustic transducers, or "EMATs") or even at a distance (such as one or more laser sources). In such a case, the sensors 11 can be positioned outside the container and / or conduit, close to and / or at a distance from the wall 2. In this context, "close" means that the distance between the wall and the sensor is between 1 µm and 50 mm, or even between 100 µm and 10 mm, or even between 1 mm and 5 mm.In this context as well, "at a distance" means that the distance between the wall and the sensor is greater than 50 mm, or even greater than 100 mm, or even greater than 500 mm.

[0105] In other alternatives, the sensors can be placed inside the container and / or conduit 1, for example on wall 2 or at a distance from it.

[0106] Ultrasonic sensors 11 are sensors enabling the generation and capture of ultrasonic waves propagating in the wall 2 of the container and / or conduit 1. In particular, these sensors 11 serve to generate and capture one or more guided waves in the wall 2, that is to say in the thickness of said wall 2.

[0107] For example, an illustration of such propagation is shown in Figure 9, where, in particular in Figure 9(a), a guided wave ¢ propagates in the wall 2 of the container and / or conduit 1, seen from the front, between two sensors 11 positioned one above the other, and where, in particular in Figure 9(b), a guided wave ¢ propagates in the wall 2 of the container and / or conduit 1, seen from above, between two sensors 11 positioned at a substantially similar height on said wall 2.Similarly, typically when the container and / or conduit 1 is substantially cylindrical in shape along a horizontal direction, particularly in Figure 9(c), a guided wave θ propagates in the wall 2 of the container and / or conduit 1 between two sensors 11 positioned one above the other, and where, particularly in Figure 9(d), a guided wave 0 propagates in the wall 2 of the container and / or conduit 1 between two sensors 11 positioned at a substantially similar height on said wall 2. For the sake of simplicity, the thickness of the wall 2 is not shown in figures other than [Fig.9].

[0108] Preferably, these sensors 11 are configured to excite the anti-symmetric Ao and symmetric So propagation modes of a Lamb and / or Quasi-Scholte QS wave.

[0109] Any technology can be used for these sensors, such as ultrasonic transducers exploiting the piezoelectric effect, which converts mechanical displacement into a voltage, and vice versa. The sensors can then be single-element transducers, also known as pellets, or linear or matrix multi-element transducers. In the first embodiment, these sensors are placed in contact with the wall 2, but they are also suitable for non-contact applications. In the latter case, a coupling device can be used to minimize the impedance mismatch between the wall and the medium surrounding the container and / or conduit.

[0110] Alternatively, some applications may use measurement technologies not based on the piezoelectric effect, such as optoa-acoustic technologies, for example using one or more laser vibrometers or magnetostrictive transducers.

[0111] The sensors 11 of the plurality of sensors 11 may be based, in whole or in part, on different technologies and / or combine different sensor technologies. The sensors are therefore configured to suit the application (geometry, dimensions, emission frequency, emitted wavelength, emission energy, etc.)

[0112] The position of each sensor 11 of the plurality of sensors 11 at a distance or on the container and / or conduit 2 is predefined.

[0113] The plurality of sensors 11 comprises a first sensor 11 and a second sensor 11. The first sensor 11 is arranged so as to be positioned on the wall 2 above the liquid level 5. The second sensor 11 is arranged so as to be positioned on the wall 2 below the liquid level 5. These first and second sensors 11 may alternatively be based on non-contact sensor technology. The first and / or second sensors are then positioned so as to generate a guided wave in the wall 2 from a first and / or second source point, respectively, these source points being located above and / or below the liquid level 5, respectively. These source points correspond, for example, to the respective positions of the first and / or second sensors, respectively, if these are in contact with the wall 2.

[0114] The position of the first sensor 11 and the position of the second sensor 11 on the wall are dependent on the instrumentation conditions and constraints related to the environment as well as the geometry, accessibility and size of the container and / or conduit 1. In particular, other elements of the container and / or conduit 1, such as the supply and power circuits, as well as the chassis of the device and the presence of other systems around the container and / or conduit 1 such as other containers and / or conduits, may constrain the positioning of the sensors 11.

[0115] Furthermore, the internal volume of the container and / or conduit, particularly for a fuel tank, may include an upper zone, called bubble B, and a lower zone, called puddle F. Bubble B acts as a buffer to allow sufficient time for the operator filling the container and / or conduit to stop filling so as not to exceed the capacity of the internal volume of the container and / or conduit. Puddle F serves as a fuel reserve, guaranteeing the pilot a minimum flight range to complete the flight and land the aircraft. According to one embodiment, the first sensor and the second sensor may be arranged on the external face 2e so as to be above the lower interface Bb of bubble B and below the upper interface Fh of puddle F, respectively.

[0116] The aim is to ensure that the first and second sensors are always above and below, respectively, the fuel level that we wish to measure outside the inert volume.

[0117] The relative positioning of the first sensor with respect to the second sensor does not depend on any specific conditions other than those previously mentioned. However, it is preferable that the first and second sensors be positioned on the same side of the container and / or conduit in order to promote the transmission of guided waves of one to the other. Similarly, it is preferable that the propagation path between the first and second sensors does not have a mechanical interruption, such as an impedance break, for example in the form of a attenuating polymer seal or a geometric discontinuity.

[0118] When the geometry of the container and / or conduit 1 allows, it is preferable for the first and second sensors to be substantially vertically aligned with each other along a vertical axis of the container and / or conduit, so that wave transmission occurs along a direct propagation path between these sensors. The vertical axis of the container and / or conduit is orthogonal to the plane defined by the liquid surface at its interface with the gas when the apparatus is on the ground and not in motion. In other words, when the container and / or conduit is a cylinder, the first and second sensors are positioned so as to be substantially in a plane tangent to the wall 2. This alignment simplifies the calculations of the gauging method described later.

[0119] The acquisition module 12 is connected to the plurality of sensors 11. The acquisition module 12 is configured to drive the plurality of ultrasonic sensors so as to generate a guided wave in the wall 2. Preferably, the acquisition module is connected to each sensor of the plurality of sensors.

[0120] By "connected" is understood that a connection intermediary, for example a wired or wireless connection, links the elements in question and allows the transfer of data from the elements to each other.

[0121] The guided wave generation is implemented by exciting the sensor with an excitation signal. The excitation signal is optionally digitized by the acquisition module 12. In this case, the excitation signal comprises a plurality of successive samples digitized at a predetermined sampling frequency. The sampling frequency is generally greater than or equal to twice the highest frequency of the excitation signal, so as to comply with the Shannon-Nyquist criterion.

[0122] The excitation signal can be any type of signal that allows the generation of the guided wave. The excitation signal therefore depends on the application in question. For example, the excitation signal could be a pulse, a single-frequency sinusoidal wave train, a multi-frequency sinusoidal wave train, a signal modulated around a center frequency (in English, "chirp"), a broadband signal, etc. The excitation signal preferably has a finite time support.

[0123] In the first embodiment, the excitation signal is a single-frequency sinusoidal wave train of a given excitation frequency, digitized at the data sampling frequency, and preferably greater than 1 MHz. The excitation frequency is the frequency of the sinusoid of the sinusoidal wave train. The values ​​of These different frequencies depend on the material of the container wall and / or the conduit. For example, for a 3 mm thick aluminum wall, the excitation frequency is 50 kHz for the first propagation mode and 100 kHz for the third propagation mode. The sampling frequency is then at least 500 kHz, and even greater than 1 MHz for these two propagation modes.

[0124] The processing module is also configured to acquire a signal from a guided wave, in particular one propagating through the wall, and captured by one of the sensors in the plurality of sensors. The acquired signal comprises a plurality of samples acquired at an acquisition frequency. The acquisition frequency is generally greater than or equal to the maximum frequency of the wave propagation mode captured by the sensor to be acquired, so as to comply with the Shannon-Nyquist criterion. The acquisition frequency may be equal to the sampling frequency.

[0125] The acquisition module 12 therefore comprises a processor and a memory. The memory includes instructions which, when executed by the processor, allow the digitization of the excitation signal, the generation of the guided wave, in particular in the wall, by means of a sensor of the plurality of ultrasonic sensors and / or the acquisition of the signal of a guided wave, in particular propagating in the wall.

[0126] The processing module 13 is connected to the acquisition module 12. The processing module includes memory and a processor and is configured to implement the gauging method. The processing module 13 therefore includes, in its memory, instructions which, when executed by the processor of the processing module 13, enable the implementation of the gauging method. The processing module is, for example, a computer.

[0127] The gauging method 100, as illustrated in [Fig. 2], comprises three main steps numbered 110 to 130. Method 100 may also include a preliminary step 105 to determine a wall thickness 2, if it is not predefined. The physical quantities used by method 100 are shown in [Fig. 3].

[0128] It will become apparent that the first step 110 and the second 120 are independent and can be implemented in any order or concurrently with each other. Further details are given below.

[0129] In the first embodiment, it is assumed that the properties of the liquid are homogeneous in the internal volume of the container and / or conduit 1.

[0130] The first step 110 is a step for determining the liquid level 5 in the container and / or conduit 1. The objective of this step is therefore to determine the height of the liquid in the container and / or conduit. The first step 110 comprises three substeps, numbered 111 to 113.

[0131] The proposed approach is based on measuring the propagation time of a guided wave propagating between the sensors 11 in order to deduce the liquid level. The liquid level is determined here with respect to the position of the second sensor. It is necessary to use a propagation mode sensitive to the presence of the liquid. In particular, the guided wave propagates between the sensors according to a first mode in the upper section 2a of the wall 2, above the liquid level 5, and propagates according to a second propagation mode, sensitive to the presence of the liquid, in the lower section 2b of the wall 2, below the liquid level 5. The second propagation mode may require the presence of a liquid to propagate and therefore may not exist in the upper section 2a.

[0132] Preferably, the first propagation mode is the anti-symmetric Ao mode of a Lamb guided wave and the second propagation mode is the Quasi-Scholte QS mode. The QS mode can be generated in the lower part 2b directly by the second sensor 11 or by conversion of the Ao mode at the passage of the liquid / gas interface after emission by the first sensor 11 (FB Cegla, P. Cawley, and MJS Lowe, Material property measurement using the quasi-Scholte mode - A waveguide sensor, JASA, vol. 117, 1098, 2005; FB Cegla, P. Cawley, and MJS Lowe, Fluid bulk velocity and attenuation measurements in non-Newtonian liquids using a dipstick sensor, Meas. Sci. Technok, vol. 17(2), 264, 2006). The advantage of QS mode is that it allows for better measurement accuracy than other commonly used modes.

[0133] The excitation signal is preferentially adapted to stimulate a first, second, and / or third propagation mode. It is possible to use different excitation signals to stimulate each of the first, second, and / or third propagation modes independently. It is noted that the excitation signal adapted to stimulate the first mode, in the case of the Ao mode, is also adapted to stimulate the second mode, in the case of the QS mode, and vice versa, due to the conversion of the Ao mode to the QS mode. The sensors are therefore dimensioned (diameter, emission wavelength, energy, etc.) to stimulate the first, second, and / or third mode.

[0134] Implementing substeps 111 and 112 allows the propagation speed of the first and second propagation modes to be determined. Advantageously, the proposed approach for determining these propagation speeds is self-calibrated, that is, it allows the experimental conditions at the time of measurement to be taken into account, in particular the temperature in the internal volume, and more specifically the temperature of the liquid.

[0135] Substeps 111 and 112 are independent of each other and can be implemented in any order or concurrently.

[0136] The first substep 111 is a step for determining the propagation speed of the first propagation mode, in this case the Ao mode, propagating in the upper section 2a of the wall 2. The excitation signal is therefore chosen to favor the propagation of the Ao mode.

[0137] The determination is based on the pulse-echo technique, i.e., the generation of a wave and its capture by the same sensor after reflection from a first reflector. The wave thus travels back and forth between the sensor and the first reflector. Preferably, the first reflector is an element of the container and / or conduit in contact with the upper section 2a and does not require the addition of an extra element on the inner face 2i. Alternatively, the first reflector is an additional calibrated element positioned at any location on the inner face 2i so as to be above the liquid level 5. The position of the first reflector is predefined. Preferably, the position of the first reflector is such that the transmission path between the first reflector and the first sensor is a direct path.

[0138] The wave is therefore generated by the first sensor so that it propagates according to the first mode of propagation, i.e. the Ao mode. The first reflector is here the upper surface 3 or a part thereof. Preferably, the first sensor is positioned so as to be sufficiently far from the upper surface 3 to guarantee an accurate measurement of the propagation time of the first mode of propagation, for example at a distance equal to at least two wavelengths, or even at least three wavelengths, or at least five wavelengths or even ten wavelengths of the first mode of propagation at a given frequency, for example the excitation frequency.

[0139] The distance h] between the first sensor and the first reflector, here the upper surface 3, being predefined, the distance traveled by the wave propagating according to mode Ao and reflected by the first reflector is also predefined. The propagation time 1] of the first mode along the path hv is determined by calculating the difference between the instant when the echo of the guided wave is captured, after reflection on the first reflector, and the instant of emission of this wave. In this case, the propagation speed V40 of mode Ao is then v_. y AO q

[0140] The second substep 112 is a step for determining the propagation speed of the second propagation mode, in this case the QS mode, propagating in the lower section 2b of the wall 2. The excitation signal is therefore chosen to favor the propagation of the QS mode.

[0141] The pulse-echo technique is also employed. A second reflector, different from the first reflector, is used. Preferably, the second reflector is

[0142]

[0143] a container element and / or conduit located on the lower section 2b and not requiring the addition of an extra element on the inner face 2i. Alternatively, the second reflector is an additional calibrated element positioned at any location on the inner face 2i so as to be below the liquid level 5. The position of the second reflector is predefined. Preferably, the position of the second reflector is such that the transmission path between the second reflector and the second sensor is a direct path. The wave is therefore generated by the second sensor so that it propagates according to the second propagation mode, i.e., the QS mode. The second reflector here is the lower surface 4 or a part thereof. Preferably, the second sensor is positioned so as to be sufficiently far from the lower surface 4 to guarantee an accurate measurement of the propagation time of the first propagation mode, for example at a distance h2 equal to at least two wavelengths, or even at least three wavelengths, or at least five or even ten wavelengths of the second propagation mode at a given frequency, for example the excitation frequency. Since the distance h2 between the second sensor and the second reflector, here the lower surface 4, is predefined, the distance traveled by the wave propagating in QS mode and reflected by the second reflector is also predefined. The propagation time Q of the second propagation mode along the path h2 is determined by calculating the difference between the instant when the echo of the guided wave is captured, after reflection on the second reflector, and the instant of emission of this wave. In this case, the propagation speed Vqs of the QS mode is then y_2¾.

[0144] The third substep 113 is then a liquid level determination step 5. In particular, the height H of the liquid is determined relative to the position of the second sensor. To do this, a guided wave is transmitted between the sensors 11 of the plurality of sensors such that the wave path crosses the liquid / gas interface. The wave therefore propagates according to the first propagation mode above the liquid level 5 and according to the second propagation mode below the liquid level 5, after conversion from the first mode to the second propagation mode upon passing through the liquid / gas interface.

[0145] In this first embodiment, this guided wave is generated by the first sensor and is captured by the second sensor. Since the sensor positions are predefined, the distance L12 between the first and second sensors is also predefined. The height H of the liquid is determined by f)2 - ?[2 _ , where / [2 is the time H = ; r ~ propagation of the guided wave propagating between the first and second sensors 11 according to the first mode of propagation above the liquid level 5 and according to the second mode of propagation below the liquid level 5.

[0146] The propagation time is determined by calculating the difference between the time of capture of the second mode of propagation of Fonde guided by the second sensor and the time of generation of the wave guided by the first sensor.

[0147] Alternatively, the wave can be generated by the second sensor and captured by the first sensor. In this case, the first propagation mode is generated by converting the second propagation mode at the liquid / gas interface. The height H is determined in the same way as before, and the propagation time 12 is determined by calculating the difference between the capture time of the first propagation mode of the wave guided by the first sensor and the generation time of the second Fonde propagation mode guided by the second sensor.

[0148] The liquid level 5 relative to the lower surface 4 of the container and / or conduit 1 is therefore given by the summation of the height H of liquid measured relative to the second sensor with the distance h2 of the second sensor relative to the lower surface 4.

[0149] By way of illustration, Figure 6 shows a set of signals acquired by ultrasonic guided Fonde capture by the second sensor after generation by the first sensor. The guided wave thus passes through the liquid level interface during its propagation. Each line corresponds to one of these signals, each acquired for a different liquid height H between a maximum level Hmax and a minimum level. It is observed that the propagation time of the So mode is invariant with the variation of the liquid height, while that of the Ao mode, converted to QS mode at the interface, decreases as the liquid height decreases. The Ao mode propagates here at 125 kHz.

[0150] The second step 120 is a step for determining the density of the liquid. The density can be determined from the knowledge of the propagation speed of the second propagation mode, in this case the QS mode. To do this, it is necessary to know the temperature of the wall and to have a dispersion curve of the second propagation mode as a function of this temperature. For this purpose, the second step 120 comprises at least a first and a third substep, numbered 121 and 123, and, optionally, a second substep 122.

[0151] As is known, calculating a theoretical dispersion curve requires knowledge of a number of parameters of the propagation medium, such as, for example, the wall thickness, the Young's and Poisson's moduli, and its density. It is also required to know the wall temperature and the material properties of the liquid, such as its isostatic modulus of elasticity and its density. With the exception of wall temperature and liquid density, all these parameters are predefined. The calculation of theoretical dispersion curves is used to obtain the velocity curve of the second mode, here the QS mode, at a given frequency or over a frequency range around a central emission frequency.

[0152] The first substep 121 is a step for determining the wall temperature. The proposed approach is based on measuring the propagation time of a guided wave propagating between the sensors 11 according to the third propagation mode, which is insensitive to the presence of the liquid but sensitive to temperature. The guided wave propagates in this third mode throughout the wall 2.

[0153] Preferably, the third propagation mode is the symmetric mode So of a Lamb guided wave. The guided wave propagating in mode So is generated by the first sensor and captured by the second sensor, or is generated by the second sensor and captured by the first sensor.

[0154] By way of illustration, variations in the propagation velocity of the So mode at different temperatures and in a 3 mm thick aluminum plate are shown in [Fig. 7]. One face of the plate is in contact with air, the other is in contact with either air or water. It can be seen that the presence of water has a second-order influence on the velocity of the So mode, unlike its influence on the temperature. Particularly for this reason, the So mode is preferred here for estimating the temperature of the plate, regardless of the water level.

[0155] The wall temperature is determined by inverting a dispersion curve of the third propagation mode as a function of the propagation velocity of the third guided Fonde propagation mode. The propagation velocity Vs0 of the third propagation mode is given by y _ £12. 5'0 fçQ

[0156] The propagation time t$G of the third propagation mode is determined by calculating a difference between the time of capture of the third propagation mode of the guided wave by the sensor that captures the wave and the time of generation of the third propagation mode of the guided wave by the sensor that emits the wave.

[0157] The dispersion curve is a theoretical curve, for example calculated by a numerical model or obtained by an analytical function, for example following a low frequency approximation, or an experimental curve obtained via an acquisition system, and allows the propagation speed of the third propagation mode to be determined at different frequencies at a given wall temperature.

[0158] Inversion consists, knowing the excitation frequency and the propagation speed of the third mode of propagation of the guided wave, in finding the corresponding dispersion curve to deduce the temperature. Inversion can be put This is implemented using known inversion techniques, such as inverting the analytical equation of the dispersion curve, inverting the numerical model used to calculate the dispersion curve, or searching a pre-built database of dispersion curves obtained analytically, experimentally, and / or by the numerical model. The advantage of using database-based inversion is that its implementation, once the database is built, is much faster than other approaches, and is therefore better suited for in-situ implementation of Method 100.

[0159] At a given frequency, the database can be constructed by defining ranges of variation for the wall temperature and the excitation frequency, and by determining the associated propagation velocity by reading a calculated dispersion curve, taking into account the temperature / excitation frequency pair in question. This database can be stored in the memory of the processing module 13. It is then sufficient, during substep 121, to search the database for the pair corresponding to the propagation velocity of the third propagation mode and the associated excitation frequency, in order to determine the wall temperature.

[0160] The inversion therefore consists of finding the dispersion curve whose wall temperature, from which it is calculated, induces the propagation of the third propagation mode at the generation frequency with the determined propagation speed Vço. The mechanical properties of the wall necessary for calculating the dispersion curve are predefined.

[0161] The second substep 122 is a step for determining the propagation speed of the second propagation mode, here the QS mode. This second substep 122 is implemented only if this propagation speed has not been determined in substep 112, in particular if the second step 120 is implemented before the first step 110. In this case, it is not necessary to implement the second substep 112. The propagation speed of the second mode is then determined, during the second substep 122, in the same way as in the second substep 112. The second substep 122 is therefore independent of the first substep 121 and can be implemented before, after, or concurrently with it.

[0162] The third substep 123 is then a step of determining the density of the liquid, knowing the temperature of the wall and the propagation speed of the second propagation mode, here QS. The density of the liquid is determined by knowing (through modeling or calibration measurement on known liquids) the dispersion curve of the second guided wave propagation mode and the temperature of the wall.

[0163] Density is, for example, obtained by inverting the equation of a dispersion curve of the propagation speed of the second propagation mode taking into account the determined temperature of the wall.

[0164] Inversion consists of, knowing the excitation frequency, the propagation speed of the second propagation mode, and the wall temperature, finding the corresponding dispersion curve to deduce the liquid density. Inversion can be implemented using known inversion techniques, such as inverting an analytical equation of the dispersion curve, inverting the numerical model used to determine the dispersion curve, or searching a pre-constructed database of dispersion curves obtained analytically, experimentally, and / or by the numerical model. The advantage of using inversion based on a database search is that its implementation, once the database is constructed, is much faster than other approaches, and is therefore more suitable for in-situ implementation of Method 100.

[0165] At a given frequency, the database can be constructed by defining ranges of variation for the wall temperature and the liquid density, and by determining the associated propagation velocity by reading a calculated dispersion curve, taking into account the temperature / density pair in question. This database can be stored in the memory of the processing module 13. It is then sufficient, during substep 123, to search the database for the pair corresponding to the propagation velocity of the second propagation mode, determined in substep 112 or substep 122, and the wall temperature determined in substep 121 to determine the liquid density.

[0166] The inversion therefore consists of finding the dispersion curve whose liquid density, from which it is calculated, generates the propagation of the third propagation mode at the generation frequency with the determined propagation velocity Vqs. The mechanical properties of the wall necessary for calculating the dispersion curve are predefined.

[0167] For example, at 20°C for an aluminium tank 3 mm thick, filled with a liquid, reading the dispersion curves for an excitation frequency of 50 kHz provides the propagation speed of the QS mode for different values ​​of density P, according to the table below. P (g / cm3) Vqs (m / s) 0.7 1931 0.75 1924 0.8 1918 0.85 1911 0.9 1905 0.95 1900 1 1894

[0168] At 15 °C, the different values ​​of density P are given in the following table. P (g / cm3) Vqs (m / s) 0.7 1925 0.75 1918 0.8 1912 0.85 1906 0.9 1900 0.95 1894 1 1888

[0169] Over this range of density variation, a linear law of velocity variation as a function of density P can be estimated. This law can then be used to obtain the density once the measurement Vqs has been carried out.

[0170] Statistical calculations show that, in this case, a measurement of the velocity V qs to within 1%, and knowledge of the temperature to within 5 °C, lead to the estimation of the liquid density to within approximately 13%.

[0171] This step can be repeated at several different frequencies and the result averaged to improve the accuracy of the density estimation. Alternatively, a numerical model of the dispersion curve (linking the second-mode velocity to the frequency) can be stored in the memory of the processing module 13 to accurately estimate the propagation velocity of the second mode over a whole frequency range by minimizing the difference between the experimental dispersion curve and the dispersion curve obtained by an analytical or numerical model. Indeed, the accuracy of the measurement of this velocity directly determines the accuracy of the final density estimation.

[0172] The third step 130 is a step for determining the mass of liquid carried. The mass of liquid is determined from the density determined in the second step 120, the volume of liquid in the container and / or conduit 1, more particularly by multiplying these two quantities.

[0173] The volume of liquid is determined by applying a height / volume law taking taking into account the liquid level 5 determined in the first step 110 and knowing the geometry of the tank as well as the attitude of the aircraft (yaw, pitch, roll, etc.). When the geometry of the tank is simple, such as a cylinder, the volume of liquid is given by the analytical equation of the volume of the geometry in question, one of whose dimensions is the liquid level 5. When the geometry of the tank is complex, the volume of liquid can be determined using analytical or numerical formulations via a numerical volume calculation model.

[0174] It is advantageously observed that the determination of the propagation speed of the first propagation mode, the determination of the propagation speed of the second propagation mode, and the propagation speed of the third propagation mode can be achieved by generating a single signal from one of the first or second sensors. The excitation signal is then adapted to generate these three modes simultaneously.

[0175] The mass carried is then transmitted to an operator, such as the pilot, or to an external system, for example for storing information on a memory or in order to maintain the center of gravity of the aircraft relative to the center of thrust and not unbalance the aircraft by an excess or a deficiency of fuel mass.

[0176] In a second embodiment, it is not possible to use reflectors to implement substeps 111 and 112 of determining the propagation velocities of the first and second propagation modes. In this case, the plurality of sensors 11 includes a third sensor and a fourth sensor. The third sensor is arranged so as to be positioned on the wall 2 below the liquid level 5. The fourth sensor 11 is, for its part, arranged so as to be positioned on the wall 2 above the liquid level 5. In this second embodiment, it is also assumed that the properties of the liquid are homogeneous throughout the container and / or conduit 1. In this embodiment, it is therefore not necessary for the first sensor to be positioned so as to be sufficiently far from the upper surface 3, nor for the second sensor to be positioned sufficiently far from the lower surface 4.

[0177] The position of the third sensor 11 and the position of the fourth sensor 11 on the wall 2 depend on the instrumentation conditions and constraints related to the environment as well as the geometry, accessibility, and size of the container and / or conduit 1, as with the first and second sensors. Similarly, it is preferable that the propagation path between the third and fourth sensors not have any mechanical interruption, such as an impedance break, for example in the form of a polymer attenuating seal or a geometric discontinuity.

[0178] Preferably, the fourth sensor and the third sensor are arranged on the wall 2 so as to be above the lower interface Bb of the bubble B and below the high interface Fh the puddle F, respectively.

[0179] Preferably, the fourth sensor is substantially aligned horizontally with the first sensor, for example in a plane parallel to the liquid level when the device is on the ground and not moving, so that wave transmission occurs along a direct propagation path between these sensors. Similarly, the third sensor is substantially aligned horizontally with the second sensor, for example in a plane parallel to the liquid level when the device is on the ground and not moving, so that wave transmission occurs along a direct propagation path between these sensors. In the example in [Fig. 4], the tank is cylindrical and the fourth sensor is positioned at substantially the same height as the first sensor. Similarly, the third sensor is positioned at substantially the same height as the second sensor. This alignment simplifies the calculation of the liquid level 5.It is preferable that the propagation paths between the first and fourth sensors and between the second and third sensors do not have any mechanical interruption, such as an impedance break, for example in the form of a attenuating polymer seal or a geometric discontinuity.

[0180] The relative positioning of the fourth and third sensors does not depend on any specific conditions other than those previously mentioned. However, it is preferable that the third and fourth sensors be arranged on the same side of the container and / or conduit in order to facilitate the transmission of a guided wave from one to the other.

[0181] When the geometry of the container and / or conduit 1 permits it, it is preferable that the third and fourth sensors be substantially aligned vertically with each other, along the vertical axis of the container and / or conduit, so that wave transmission occurs along a direct propagation path between these sensors. This alignment simplifies the calculation of the liquid level 5.

[0182] In this second embodiment, the determination of the propagation speeds of the first mode and the second mode, in this case of the Ao and QS modes, is not based on a "pulse-echo" type measurement using known reflectors, but is based on a direct measurement in transmission of a guided wave in the wall between the first and fourth sensors and between the second and third sensors, respectively.

[0183] Thus, in substep 111, the propagation speed of the first propagation mode, i.e., mode A0, is determined by y^ — , where L14 is the distance between the The first sensor and the fourth sensor, and 14, is the propagation time of the first propagation mode between the first and fourth sensors. The propagation time ?14 is determined by calculating the difference between the time of capture of the first mode of propagation of the wave guided by the sensor that captures the wave, that is to say the

[0184]

[0185] first or fourth sensor, and the generation time of said first mode of propagation of Fonde guided by the sensor that emits the wave, that is to say the fourth or first sensor, respectively. Similarly, in substep 112, the propagation speed of the second propagation mode, i.e., the QS mode, is determined by y_, where -^23 is the distance between the second sensor and the third sensor and ^3 is the propagation time of the second propagation mode between the second and third sensors and is determined by calculating a difference between the time of capture of the second propagation mode of the guided wave by the sensor that captures the wave, i.e. the second or the third sensor, and the time of generation of said second propagation mode of the guided wave by the sensor that emits the wave, i.e. the third or the second sensor, respectively. In substep 113, the height H of liquid is then determined by

[0186] This equation is given in the case where the guided wave is transmitted between the first and second sensors.

[0187] Alternatively, the wave can be generated by the second sensor and captured by the first sensor. The height H is determined according to the same equation and the propagation time f]2 is determined by calculating the difference between the capture time of the first wave propagation mode guided by the first sensor and the generation time of the second wave propagation mode guided by the second sensor.

[0188] In substep 113, guided melt can alternatively be transmitted between the fourth and third sensors. The liquid height H is then determined by ~ lx; -L xr. ' °û ^34 is the distance between the fourth sensor and the 'A l,. Av 14 third sensor and ^34 is the propagation time of guided Fonde propagating between the third and fourth sensors 11 according to the first propagation mode above the liquid level 5 and according to the second propagation mode below the liquid level 5. The propagation time ^34 is determined by calculating a difference between the capture time of the second propagation mode of guided Fonde by the third sensor and the generation time of guided Fonde by the fourth sensor.

[0189] Alternatively, Fonde can be generated by the third sensor and captured by the fourth sensor. In this case, the first propagation mode is generated by conversion of the second propagation mode at the liquid / gas interface passage. The height H is determined in the same way as before and the propagation time ^34 is determined by calculating the difference between the time of capture of the first propagation mode of the wave guided by the fourth sensor and the time of generation of the second propagation mode of the wave guided by the third sensor.

[0190] In a third embodiment, compatible with the preceding embodiments, the measurements performed at the various stages of Method 100 can be based on the capture of the generated waves by several sensors. In this case, the plurality of sensors comprises one or more intermediate sensors 1 li, arranged on the wall 2 so as to be positioned between the first and second sensors, as illustrated in [Fig. 5]. The intermediate sensors lili can be regularly spaced at intervals given in units of length. The interval can be constant or can vary depending on the position along the wall 2. Depending on the sensor technology used, these intermediate sensors can be arranged at a distance from or in contact with the wall 2 and can be placed inside or outside the container and / or conduit.

[0191] The advantage then lies in capturing the guided wave generated along its path between the first and second sensors by the intermediate sensors 1 li, which is beneficial if the container and / or conduit is large. Furthermore, these intermediate sensors provide measurement redundancy in case of failure of certain sensors, particularly the first and second sensors and / or the third and fourth sensors, as applicable. This also allows for the detection of variations in the propagation speed of Fonde and its modes by measuring the associated propagation times. A stratification of propagation speeds is thus obtained. It is then possible to determine a propagation speed gradient for one or more of the first, second, or third modes of guided Fonde propagation in the wall 2.These gradients can be obtained by interpolation, using any interpolation method, for example by means of a linear function, of the propagation velocity values ​​determined by the measurement of the sensors 11 of the plurality of sensors 11, in particular the intermediate sensors 1 li. Therefore, a possible temperature gradient is taken into account when determining the propagation velocities.

[0192] The propagation velocity gradient can thus be taken into account for the first, second and third modes in the calculation of the height H of liquid, thereby improving the accuracy and reliability of the calculation.

[0193] Furthermore, having propagation velocity gradients is particularly advantageous for applications where the properties of the liquid in the container and / or The fuel in the container and / or pipe is not homogeneous. For example, during its various stops, an aircraft refuels at different refueling points where the properties of the refueled fuel differ. This is particularly true of the fuel density. Using intermediate sensors to determine the propagation velocity gradient of the first, second, and / or third modes allows for the determination of a density gradient of the fuel in the container and / or pipe. Consequently, it is possible to determine with high accuracy the mass of fuel carried in the container and / or pipe by applying the height / volume law, taking into account the density gradient.

[0194] It is also possible to arrange the intermediate sensors 1 li between the fourth and third sensors on the wall 2. This makes it possible to form sensor pairs combining one of the intermediate sensors 1 li arranged between the first and second sensors with one of the intermediate sensors lli arranged between the fourth and third sensors. Each pair is such that the sensors of said pair are placed substantially at the same height and / or on the same horizontal plane, for example parallel to the liquid level when the device is on the ground and not moving. The advantage is being able to evaluate with high precision the gradient of the propagation velocities of the first and second modes calculated according to substeps 111 and 112.

[0195] In a fourth embodiment, compatible with the previous embodiments, the method 100 includes the preliminary step 105 which is a step of determining the thickness of the wall 2 of the container and / or conduit 1. The thickness is the distance separating the external face 2e and the internal face 2i of the wall 2.

[0196] The thickness is determined by calibration using a known fluid. The thickness is, for example, obtained by inverting the equation of a dispersion curve for the propagation velocity of the first, second, and / or third propagation mode while the container and / or conduit contains a known fluid. The known fluid is a fluid whose properties are predefined, in particular its density. The temperature of the wall and within the volume of the container and / or conduit, including the known fluid, is predefined. Preferably, this determination is carried out by propagation of the first propagation mode in the wall, i.e., mode Ao, which is the most sensitive to thickness, while the container and / or conduit is filled with a gas, in particular air.

[0197] Inversion consists, knowing the excitation frequency and the propagation speed of the propagation mode in question, preferably the first propagation mode, in finding the corresponding dispersion curve to deduce the wall thickness. Inversion can be implemented using known inversion techniques, such as the inversion of an analytical equation of the curve of Dispersion, the inversion of the numerical model used to determine the dispersion curve, or searching a pre-constructed database of dispersion curves obtained analytically, experimentally, and / or by the numerical model. The advantage of using an inversion based on a database search is that its implementation, once the database is built, is much faster than other approaches, and is therefore better suited for in-situ implementation of Method 100.

[0198] At a given frequency, the database can be constructed by defining ranges of variation for the wall thickness and for the excitation frequency, and by determining the associated propagation velocity by reading a calculated dispersion curve, taking into account the thickness / excitation frequency pair in question. This database can be stored in the memory of the processing module 13. It is then sufficient, during the preliminary step 105, to search the database for the pair corresponding to the propagation velocity of the propagation mode concerned, here the first propagation mode, and the associated excitation frequency, in order to determine the wall thickness.

[0199] The inversion therefore consists of finding the dispersion curve whose wall thickness, from which it is calculated, causes the propagation of the third propagation mode at the generation frequency with the determined propagation speed VA0. The mechanical properties of the wall necessary for calculating the dispersion curve are predefined.

[0200] Alternatively, the thickness is determined via a direct measurement, for example using an ultrasonic probe.

[0201] Advantageously, this preliminary step only needs to be implemented once, preferably before the first implementation of steps 110 to 130 of method 100.

[0202] This embodiment can be combined with the embodiment comprising the intermediate sensors 1 li so as to evaluate the wall thickness 2 over several sections, each section being delimited by two successive intermediate sensors 1 li. This variant makes it possible to determine the wall thickness precisely when it is not constant between the first and second sensors and / or between the fourth and third sensors.

[0203] In a fifth embodiment, compatible with the preceding embodiments, the excitation signal is a broadband signal. This allows the first, second, and third propagation modes to be excited at several excitation frequencies. It is then possible to average the measurements of the different propagation times involved and thus improve the resolution of the propagation times determined and necessary for calculating the different propagation speeds involved. It is It is possible to use bandpass filtering, following known approaches, in order to isolate the excitation frequency or frequencies of each of the modes in order to calculate their respective propagation speeds.

[0204] In a sixth embodiment, compatible with embodiments two through five, one or more point levels are determined. These point levels indicate whether or not liquid is present at the sensor. The determination of the point levels is implemented by generating a transmitted wave between two sensors positioned at substantially the same height, for example, between the first and fourth sensors and / or between the second and third sensors and / or between the sensors of a pair of intermediate sensors 1 1. A variation in the propagation speed of the A0 mode, due to its conversion to the QS mode, thus allows the presence of liquid to be detected.

[0205] In a seventh embodiment, compatible with the preceding embodiments, the method further includes a step (not shown) of determining the level of liquid in bubble B and / or in puddle F. These levels are determined by means of pulse-echo measurement using a wave generated by the first or second sensors and reflected by the first or second reflector, respectively.

[0206] In the bubble, the liquid level is then given by t -1 ' with H - = t\r the propagation time of the guided wave propagating between the first sensor and the first reflector according to the second mode, here QS, between the first sensor and the liquid level, and according to the first mode, here Ao, between the liquid level and the first reflector.

[0207] In the puddle, the liquid level is then given by tv - 2ï A , with H - Ves V,w 2¾ " 2ht hr is the propagation time of the guided wave propagating between the second sensor and the second reflector according to the first mode, here Ao, between the second sensor and the liquid level, and according to the second mode, here QS, between the liquid level and the second reflector.

[0208] In one embodiment, the density of the liquid is determined by measuring the electrical impedance of one of the piezoelectric sensors positioned below the liquid level, for example the second sensor. The electrical impedance measurement is performed across the sensor terminals over a frequency range, possibly only at a given frequency, for example at a sensor resonance frequency.

[0209] Such an impedance measurement varies with the transfer of mechanical energy to the liquid, which depends in particular on the ratio between the acoustic impedance of the mechanical wall and that of the liquid, the acoustic impedance of the liquid being given by the product p XV, with P the density of the liquid and V the speed of propagation of sound in the liquid.

[0210] A one-dimensional model, such as that presented in I. Perrissin-Fabert Et al., Nondes-structive evaluation of materials using an inserted piezoelectric sensor-correlation with hardness measurements" IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, vol. 42(4), p. 641-648, 1995, can then be used to reverse the density of the liquid.

[0211] Other more complex models, such as possibly a three-dimensional numerical model, may also be used.

[0212] This variant is particularly advantageous for a container and / or conduit whose wall is flexible and thin, for example for a helicopter tank, which makes it possible to reduce the impedance break between the wall and the liquid contained in the tank and makes the method more sensitive to the density of said liquid.

[0213] In one embodiment, the wall temperature is directly measured by means of one or more thermocouples, or one or more sensors from another temperature measurement technology, positioned outside the container and / or conducted on the wall 2.

[0214] For an aeronautical application, it is possible to duplicate the plurality of sensors in the gauging system to take into account the aircraft's attitude when calculating the volume of fuel on board. For example, a first plurality of sensors and a second plurality of sensors, each comprising the sensors mentioned above, are positioned on different sides of the tank. This second plurality of sensors also provides a backup data acquisition system if some of the sensors in the first plurality are defective.

[0215] In some embodiments, since step 110 is independent of steps 120 and 130, the latter are not carried out, and only the determination, step 110, of the liquid level in the container and / or conduit is performed. In this case, method 100 is a method for determining the liquid level in the container and / or conduit, which includes only the implementation of step 110, as well as embodiments and alternatives concerning the calculation of the liquid level.

[0216] In some embodiments, to determine the mass of liquid on board, the liquid level is determined or known from another source using a similar or different approach than that described in step 110. In this case, it is possible to implement only steps 120 and 130 of method 100 for gauging the mass of liquid. In such a case, there is absolutely no need to use the first and second steps. Sensors 11. Indeed, a single sensor may be sufficient to implement steps 120 and 130 of Method 100 for gauging the mass of the liquid. The plurality of sensors is then at least one sensor, which has no specific positional constraints other than those required to implement steps 120 and 130. For example, this at least one sensor could be the second sensor. Also by way of example, when necessary, the at least one sensor could include the first and second sensors, and sometimes even the third and fourth sensors.

[0217] As an alternative to step 110, the first sensor 11 and the second sensor 11 are not necessarily arranged so as to be positioned above and below the liquid level 5, respectively. Rather, it is simply required that these two sensors be positioned on the wall 2, or at a distance, depending on the sensor technology used.

[0218] The position of the first and second sensors also depends on the instrumentation conditions and constraints, and they can be arranged so as to be above the lower interface Bb of the bubble B and below the upper interface Fh of the puddle F, respectively. It is also possible for the first and second sensors to be arranged on the same side of the container and / or conduit and for the path between these sensors to be uninterrupted.

[0219] These two sensors can be substantially aligned horizontally with each other along a horizontal axis of the container and / or conduit, so that wave transmission occurs along a direct propagation path between these sensors within the wall. The horizontal axis of the container and / or conduit is parallel to the plane defined by the liquid surface at its interface with the gas when the device is on the ground and not in motion. In other words, when the container and / or conduit is a cylinder, the first and second sensors are positioned so as to be substantially in a plane orthogonal to the wall 2. This alignment also simplifies the calculations of the gauging method.

[0220] By way of example, these sensors make it possible to determine a point level. The liquid level is then alternatively determined via a step of estimating the point level of liquid in the container and / or conduit. By "point level" is understood an estimate of the liquid level relative to a threshold above or below which the liquid level in the tank is located. It is therefore a binary estimation and less precise than the level determination proposed in step 110. This point level is determined by the emission by the first sensor and / or the second sensor of a wave, which is captured by the second sensor and / or the first sensor, respectively. In this case, the first and second sensors are positioned so as to be substantially aligned along a horizontal line, to form the position of the point level threshold. Thus, when the wave

[0221] When the liquid level is above the sensor position, this wave propagates according to the second propagation mode. Conversely, when the liquid level is below the sensor position, this wave propagates according to the first propagation mode. Since these two propagation modes have different speeds, it is possible to distinguish in binary terms whether the liquid level is above or below the sensor position, as the first propagation mode is generated when there is no liquid at the level of the propagation path, while the second mode is generated only when there is liquid at the level of this path.To do this, it is sufficient to determine the propagation time of the first or second propagation mode according to which the wave propagates between the sensors, to determine a propagation speed associated with this propagation, and then to compare this determined speed with a reference speed. This comparison then makes it possible to discriminate whether the determined speed corresponds to that of the first propagation mode or to that of the second propagation mode. For illustration, as shown in Figure 8, consider that the first sensor 11 and the second sensor 11 are horizontally aligned and separated by a known distance L12. These two sensors are positioned at a height h from the lower surface 4. In the example in Figure 8a), the wave propagates according to the second mode of propagation, while in the example in Figure 8b), it propagates according to the first mode of propagation. The propagation speed V2 to be discriminated for the wave propagating between the two sensors is determined by y12, where is the propagation time of said wave between the two sensors. one way.

[0222] To perform the comparison, the reference velocity can be a predetermined velocity of the propagation speed of the first or second Fonde propagation mode in the wall. This predetermined velocity can be estimated theoretically via an analytical or numerical model, knowing the properties of the wall 2 and the liquid, or evaluated experimentally, for example, according to the implementation methods of steps 111 and / or 112 described above. Thus, when a distance between the propagation velocity Vi2 and the reference velocity is less than a predefined threshold, it is deduced that this propagation velocity V12 corresponds to the reference propagation velocity (which can be that of the first or second mode).

[0223] Conversely, when this distance is greater than the predefined threshold, it is deduced that the propagation speed V12 does not correspond to the reference propagation speed (that of the first or second mode) but corresponds to the propagation speed of the other propagation mode (that of the second or first mode, res (respectively). It is observed that it is possible to predetermine the propagation speeds of the first and second propagation modes, according to the aforementioned methods. In this case, the propagation speed Vi2 corresponds to the propagation speed of the first or second mode relative to which a calculated distance is the smallest, or less than, the predetermined threshold.

[0224] Alternatively, the reference velocity is a velocity whose value lies between the propagation velocity of the first propagation mode and the propagation velocity of the second propagation mode. For example, it is a velocity sufficiently far removed from those of the two modes in question so that it cannot be confused with the respective velocities of these modes. For example, this reference velocity is the midpoint of the interval defined by the respective velocities of the two modes. Thus, when the propagation velocity Vi2 is less than the reference velocity, the propagation velocity V12 is considered to correspond to that of the second propagation mode, since this mode propagates more slowly than the first propagation mode.Conversely, when the propagation speed V12 is greater than the reference speed, the propagation speed Vs2 is considered to correspond to that of the first propagation mode.

[0225] Consequently, when the propagation speed V12 corresponds to the propagation speed of the first propagation mode, the liquid level is lower than the point level defined by the height h of the sensors 11 with the lower surface, and when the propagation speed V12 corresponds to the propagation speed of the second propagation mode, the liquid level is higher than the point level defined by the height h.

[0226] Subsequently, the point level indication makes it possible to determine that the level of the liquid on board is at least greater than or equal to that of the liquid when the latter has a level above or equal to the point level (second identified propagation mode), or that the level of the liquid on board is at least less than that of the liquid when the latter is below the point level (first identified propagation mode).

[0227] In some embodiments, the system includes an arrangement in the form of an intermediate waveguide. This intermediate waveguide serves to transmit the different waves, according to the first, second and / or third mode of propagation, from outside the container and / or conduit 1 into the wall 2 thereof.

Claims

Demands

1. Method (100) for determining the level of a liquid in a container and / or conduit (1) comprising: - a wall (2), in particular with an inner face (2i) and an outer face (2e), the wall (2) delimiting an internal volume of the container and / or conduit (1) containing the liquid, and - a plurality of ultrasonic sensors (11) comprising at least a first sensor (11) positioned above the liquid level (5) and at least a second sensor (11) positioned below the liquid level (5), the liquid level (5) in the container and / or conduit (1) being determined (110) from: - The propagation speed of a first propagation mode determined (111) by propagation of a guided wave in the wall (2) above the liquid level (5) and captured by the first sensor (11);- The propagation speed of a second propagation mode determined (112) by propagation of a guided wave in the wall (2) below the liquid level (5) and captured by the second sensor (11); and - The propagation time of a guided wave generated (113) by the first and / or the second sensor (11) propagating in the wall (2) according to the first propagation mode above the liquid level (5) and according to the second propagation mode below the liquid level (5).

2. Method (100) according to the preceding claim, wherein the liquid is a fuel.

3. Method (100) according to any one of the preceding claims, wherein: - The first propagation mode is the antisymmetric A o mode of a guided Lamb wave; - The second propagation mode is the Quasi-Scholte mode of a guided elastic wave.

4. Method (100) according to any one of the preceding claims, wherein: - The propagation speed of the first propagation mode is estimated (111) by generation and then capture of a wave guided by the first sensor (11) after reflection on a first reflector located on the wall (2), in particular the inner face (2i), and above the liquid level, such that y — 3Ù, where is the distance between the first sensor (11) and the first reflector and is the round-trip propagation time of the first propagation mode between the first sensor (11) and the first reflector;- The propagation speed Vqs of the second propagation mode is estimated (112) by generation and then capture of a wave guided by the second sensor (11) after reflection on a second reflector located on the wall (2), in particular the inner face (2i), and below the liquid level, such as y _ 3^2, where h2 is the distance between the second sensor (11) and the second reflector and h is the round-trip propagation time of the second propagation mode between the second sensor (11) and the second reflector; and - The height H of the liquid level (5) relative to the second sensor (11) is determined (113) by t|2A H — t;~ t-, ' Lo 2¾ " 2h, where ?i2 is the propagation time of the guided wave propagating between the first and second sensors (11) according to the first mode of propagation above the liquid level (5) and according to the second mode of propagation below the liquid level (5), and Ll2 is the distance between the first sensor (11) and the second sensor (11).;

5. Method (100) according to claim 4, wherein the first reflector is at least a part of the upper surface of the container and / or conduit (1) and / or the second reflector is at least a part of the lower surface of the container and / or conduit (1).

6. Method (100) according to any one of claims 1 to 3, wherein the plurality of sensors (11) further comprises a third sensor (11) arranged below the liquid level (5) and a fourth sensor (11) arranged above the liquid level, the first and fourth sensors (11) being positioned substantially at the same height, and the second and third sensors (11) being positioned substantially at the same height, and in which: - The propagation speed of the first propagation mode is estimated (111) by capturing a guided wave transmitted between the first and fourth sensors (11), such that v — ill, where is the distance between the first and fourth sensors (11), and / ¼ is the propagation time of the first mode of the transmitted guided wave to travel the distance L14;- The propagation speed Vqs of the second propagation mode is estimated (112) by capturing a guided wave transmitted between the second and third sensors (11), such that = ^22, where L23 is the distance between the second and third sensors (11), and ^3 is the propagation time of the second mode of the transmitted guided wave to travel the distance ^-23; and - The height H of the liquid level (5) relative to the second sensor (11) is determined (113) by „ where ?i2 is the propagation time of the guided wave propagating between the first and second sensors (11) according to the first propagation mode above the liquid level (5) and according to the second propagation mode below the liquid level (5), and L32 is the distance between the first sensor (11) and the second sensor (H).;

7. Method (100) according to any one of the preceding claims, wherein the first propagation mode and / or the second propagation mode are generated by means of a broadband excitation signal.

8. Method (100) according to any one of the preceding claims, wherein the plurality of sensors (11) further comprises an intermediate sensor (11) disposed at a distance from the wall (2) or on the wall (2), in particular on the outer face (2e), and positioned between the first and second sensors (11), and the method (100) comprising the determination of a gradient of the propagation speed of the first and / or second propagation modes from the propagation time of the first and / or second propagation modes, respectively, by means of the intermediate sensor (1 li).

9. System for determining a liquid level in a container and / or conduit (1), the container and / or conduit (1) comprising a wall (2) with an inner face (2i) and an outer face (2e), the inner face (2i) of the wall (2) delimiting an internal volume of the container and / or conduit (1) containing the liquid, the system comprising: - A plurality of ultrasonic sensors (11) disposed at a distance from the wall (2) and / or on the wall (2), comprising: • A first sensor (11), positioned above the liquid level (5); and • A second sensor (11), positioned below the liquid level (5); - An acquisition module connected to the plurality of ultrasonic sensors (11) and configured to drive the plurality of ultrasonic sensors (11) so as to generate a guided wave and / or to acquire samples of a guided wave captured by one of the sensors (11) of the plurality of ultrasonic sensors (11);and - A processing module connected to the acquisition module and configured to implement method (100) according to any one of claims 1 to 8 from the acquired samples.;

10. Computer program product comprising instructions which, when the program is executed on a computer, cause the computer to carry out the steps of the method according to any one of claims 1 to 8.

11. A computer-readable recording medium comprising instructions which, when executed by a computer, cause the computer to carry out the steps of the method according to any one of claims 1 to 8.

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