A filling level monitoring device for fluid gas containers, a hydrogen tank, and an aircraft including such a hydrogen tank.
The fill level monitoring device in fluid tanks, utilizing exciters, sensors, and processors to measure resonant frequencies and spatial orientations, addresses the inaccuracy of conventional methods, ensuring precise fuel level determination in aircraft.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- AIRBUS SOCIETE PAS AXIONS SIMPLIFIER
- Filing Date
- 2023-05-10
- Publication Date
- 2026-05-19
AI Technical Summary
Existing methods for monitoring the fill level of fluid tanks, particularly in aircraft, are inaccurate due to changing gravitational vectors and flight orientations, making it difficult to determine the precise amount of fuel, especially for low-temperature fuels like liquid hydrogen.
A fill level monitoring device using exciters, sensors, and processors to measure the resonant frequency and spatial orientation of the fluid, which includes a signal source to generate input signals, sensors to detect vibrations, and a processor to extract resonant frequencies, combined with spatial orientation and acceleration sensors to determine the fill level accurately.
Enables accurate and continuous monitoring of the fill level in fluid tanks under varying flight conditions, enhancing safety and reliability for aircraft using alternative fuels.
Smart Images
Figure 0007862604000003 
Figure 0007862604000004 
Figure 0007862604000005
Abstract
Description
Technical Field
[0001] This disclosure relates to a fill level monitoring device for a fluid tank, and more particularly to a hydrogen tank for use in an aircraft having such a monitoring device.
Background Art
[0002] From the perspective of increasing environmental protection efforts, alternative propulsion sources for aircraft are being developed. Such alternative propulsion sources may use alternative fuels (e.g., liquid hydrogen) other than kerosene fuel that cannot be stored in conventional fuel tanks. Therefore, for example, it is necessary to store hydrogen fuel or other liquid gas fuels in a suitable tank that can withstand the necessary internal pressure and low temperature (e.g., about 20K) required to store gas fuel in a liquid state. However, for safety reasons, regardless of the fuel type contained in such a fuel tank, it is also necessary to accurately monitor the fill level of the fuel tank at all times (e.g., in real time). Currently, the fill level of a fluid tank can be determined, for example, by measuring the weight of the tank or by indirectly monitoring the flow rate of the fuel exiting the tank. However, these methods may not be very accurate or may not be suitable for use in aircraft applications. Aircraft may, for example, be subject to altitude changes, and during the ascent or descent of the flight portion of the aircraft, the gravitational vector may not be constant with respect to the fuel tank, causing difficulties in determining the accurate weight value of the fuel tank and thus the accurate fill level of the fuel tank. The same applies to curved (e.g., non-linear) flight portions where the aircraft changes its flight vector.
Summary of the Invention
Problems to be Solved by the Invention
[0003] An object is to provide accurate monitoring of the fuel level in a fluid tank for use in an aircraft.
Means for Solving the Problems
[0004] This objective is resolved by the subject matter of the disclosure herein.
[0005] According to a first aspect, a fill level monitoring device is provided for monitoring the fill level of a container for a fluid. The fill level monitoring device includes at least one exciter, at least one sensor, a signal source, a processor, at least one spatial orientation and acceleration sensor, and a fill level indicator. At least one spatial orientation and acceleration sensor is connected to the processor and configured to measure the spatial orientation of the fluid in the container. The signal source is connected to at least one exciter and configured to generate an input signal containing a number of frequency components. At least one sensor is connected to the processor and configured to detect vibrations in the container, generate a corresponding vibration signal, and transmit the vibration signal to the processor. The processor is configured to compare the vibration signal with the input signal and extract a resonant frequency. The fill level indicator is configured to receive the extracted resonant frequency from the processor and to receive the spatial orientation of the fluid in the container from at least one spatial orientation and acceleration sensor. The fill level indicator is configured to determine the current fill level of the fluid in the container based on the extracted resonant frequency and the spatial orientation of the container.
[0006] Such a fill level monitoring device may be used in any container for liquids, such as a gas bottle or a container for hydrogen. However, the fill level monitoring device is not limited to hydrogen containers. The fill level monitoring device may be used in containers for, for example, liquefied petroleum gas (LPG), methane gas, or any other fluid stored under pressure in liquefied form. Furthermore, the fill level monitoring device may be used in ordinary liquid tanks. Generally, as used herein, the term fluid includes liquids (e.g., pressurized gas in liquid form), mixtures of liquids and gases, i.e., container contents in which both phase states (liquid and gas) exist simultaneously, and pure gases.
[0007] Generally, as with any other specific structure, a fluid storage container, under force-based excitation, exhibits a characteristic oscillation or oscillation pattern in which the amplitude of the oscillation or vibration is maximum in a specific frequency range. Some of these so-called resonant frequencies depend solely on the structure of the container itself and are independent of the contents of the container, while other resonant frequencies can be specifically assigned to the stored contents. In particular, liquefied gas fillings (e.g., liquid hydrogen) alter the specific resonant frequencies of the container, and the change in frequency is proportional to the filling level of the container, i.e., the change in the mass and / or volume of the contents. Therefore, the filling level of the container may be accurately determined by monitoring the resonant frequency of the container.
[0008] The container may be, for example, a component of the tank that actually holds the (fluid) contents of the tank (e.g., a pressure-resistant gas bottle or other suitable structure). In particular, the container may have an axisymmetric shape, although other shapes are also possible.
[0009] The signal source, or rather, the output terminal of the signal source, is connected to at least one exciter to generate an electrical signal having a predetermined signal pattern (e.g., an input signal for the exciter). In particular, the signal source generates an electrical signal containing a number of different frequencies within a range of resonant frequencies corresponding to frequency variations at any possible filling level of the container. As mentioned above, the specific resonant frequency of a filled container depends on the filling level of the container. Thus, each filling level of the container has a characteristic pattern of resonant frequencies that directly corresponds to each filling level and may also depend on the spatial orientation of the fluid in the tank. The signal source may output a signal having a uniformly distributed spectral distribution (e.g., a white noise signal), for example. However, other signal shapes containing each frequency are also possible.
[0010] At least one exciter may be any element or device suitable for mechanically exciting the vessel, i.e., suitable for vibrating or oscillating the vessel. In particular, the exciter may be directly mounted on the vessel and may be configured to vibrate in response to an electrical signal applied to it. However, it is not always necessary for the exciter to be directly mounted on the vessel; the exciter may be, for example, a loudspeaker or similar device that emits sound waves. In such a configuration, the speaker's emission direction may be directed towards the vessel, and as a result, the emitted sound waves coupled to the vessel mechanically excite the vessel. Furthermore, as described later, instead of an additional exciter, aircraft noise generated by a turbine, pump, etc., may be directly coupled to the vessel and thus function as an exciter. Since at least one exciter is connected to the output terminal of the signal source, the electrical signal output by the signal source (e.g., an input signal for the exciter) is converted into each mechanical vibration or oscillation coupled to the vessel by at least one exciter. As will be readily apparent to those skilled in the art, the frequency components of the input signal corresponding to the resonant frequency of the container, or rather the system of the container and its contents, at a given time, indicate the maximum relative amplitude of the oscillation or vibration of the container, but do not indicate other frequency components.
[0011] At least one sensor may be any detection or sensor element suitable for detecting vibration or oscillation of the container (or, more commonly, detecting changes in the structural dynamics of the container, or changes in the physical properties of the container wall that can be used because they correlate with changes in the dynamics of the container) and generating each electrical signal (in particular, a signal containing the frequency components of the oscillation or vibration pattern of the container). These signals are input to the processor.
[0012] At least one spatial orientation and acceleration sensor may be any sensor or sensor array capable of detecting the spatial orientation of the fluid in the container. Such a sensor or sensor array may, in particular, determine the orientation of the fluid in the container with respect to any suitable coordinate system. In aircraft applications, for example, the spatial orientation and acceleration sensor may determine the orientation of the fluid in the container with respect to the yaw, pitch, and roll axes of the aircraft. The spatial orientation and acceleration sensor may be directly mounted on the container or may be part of a surrounding structure (e.g., the aircraft). More specifically, instead of separate spatial orientation and acceleration sensors mounted on the container, signals from yaw, pitch, and roll axis sensors already present on the aircraft may be used to determine the orientation of the fluid in the container based on the orientation of the surrounding structure, which is determined by the orientation of the surrounding structure and the known relative orientation of the container with respect to the surrounding structure.
[0013] Furthermore, we may consider aircraft acceleration data related to other aerial maneuvers of the aircraft, for example, forces captured by a dense curve, obtained from at least one spatial orientation and acceleration sensor. Moreover, the corresponding forces cause a changing distribution of the fluid in the container, and therefore a change in the resonant frequency pattern.
[0014] Generally, the resonant frequency of a filled container may depend on the orientation of the fluid within the container relative to the gravitational and aircraft acceleration vectors. This is because different orientations of the container relative to these vectors result in the fluid being stored in different orientations relative to the container. Generally, the resonant frequency of a filled container changes depending on which region of the inner wall of the container is in contact with the fluid. This is because a change in the orientation of the fluid within the container causes a change or shift in the resonant frequency. Therefore, in particular, the measurement signals of a single sensor mounted at different positions on the container will change with changes in the orientation of the fluid within the container. Furthermore, a resonant frequency that does not show a shift in one orientation of the container may show a shift in a different orientation of the container, and vice versa. Thus, different resonant frequency patterns may occur, for example, at different flight orientations of the aircraft and at different acceleration states of the aircraft. This is a result of the fluid aligning within the container with respect to the superposition of all forces acting on the aircraft, particularly those taken in by gravity and the aircraft's acceleration. As the aircraft ascends or descends, for example, the pitch angle of the container relative to the gravity vector changes, causing a shift in the fluid and, consequently, a shift in the resonant frequency, as the oscillation propagates differently within the fluid in the container. Furthermore, as mentioned above, aircraft acceleration data may be utilized. In detail, different orientations of the fluid within the container cause different resonant modes due to changes in the structural dynamics of the container resulting from different distributions of the fluid within the container. These effects can be taken into account when determining the filling level of the container, as will be discussed further later, by using one or more spatial orientation and acceleration sensors (perhaps together with sensor data from, for example, the aircraft's acceleration sensors).
[0015] Furthermore, since the pressure inside the container changes with temperature, the container temperature may be taken into consideration when determining the filling level. This may also cause a change in the resonant frequency of the container. For example, as described later, the container temperature may be described in the same way as the accelerator by being included in the corresponding reference data or machine learning algorithm. Instead of considering temperature, or even further, the pressure inside the tank may be used directly. Therefore, the filling level monitoring system may further include corresponding temperature and / or pressure sensors.
[0016] Both the processor and the filling level indicator may be any computerized device capable of analyzing electrical signals, particularly by performing spectral or modal analysis. The unit may be, for example, a general-purpose computer having CPU and memory components well known in the art. Furthermore, the unit may be any other microcomputer device (e.g., an ASIC, FPGA, or TPU device). The processor receives an output signal (i.e., a vibration signal) from at least one sensor and runs a data analysis algorithm to calculate the frequency components of the signal received from at least one sensor. Furthermore, the processor receives and analyzes an input signal from a signal source and calculates the frequency components contained in the input signal. However, instead of using the input signal directly, a sensor signal from a corresponding feedback sensor in the exciter may be used. For example, the frequency components of the input signal and vibration signal may be determined by running a Fast Fourier Transform (FFT) algorithm or any other spectral analysis algorithm on the input signal and vibration signal to generate corresponding spectral functions that show the signal components over frequency. The actual resonant frequency of the vessel may then be determined or extracted, by comparing the spectral functions of the vibration signal and the input signal to generate an extracted resonant frequency. Such comparisons may also be achieved, for example, by calculating the frequency response function (FRF), as will be discussed further later. Since the signal component having the resonant frequency of the container is amplified (as described above), other signal components are not amplified or are further attenuated, but their resonant frequencies (or resonant frequency patterns) can be estimated by comparing the spectral functions of the vibration signal and the input signal. The extracted resonant frequencies or resonant frequency patterns are then passed to the fill level indicator.
[0017] The fill level indicator receives an extracted resonant frequency from the processor and the current spatial orientation of the fluid in the container from at least one spatial orientation and acceleration sensor. As described above, the spatial orientation of the fluid in the container affects the resonant frequency for a particular fill level. Therefore, the fill level indicator considers the spatial orientation and acceleration of the container when determining the actual fill level of the container. For example, the fill level indicator may have a memory lookup table of resonant frequencies or resonant frequency patterns for all possible spatial orientations of the fluid in the container (or for a subset of such possible positions of interest). Furthermore, if temperature and / or pressure data are also considered, the fill level indicator may have a memory lookup table of resonant frequencies or resonant frequency patterns for all possible temperatures and / or pressures of the container. The actual fill level of the container may then be determined, for example, by correlating or matching the extracted resonant frequency with a memory reference resonant frequency pattern. However, a fill level indicator does not necessarily need to use such a lookup table; rather, it uses a mathematical model of the container's structural dynamics and calculates the corresponding reference resonant frequency pattern by correlating or matching the extracted resonant frequencies with this model's reference resonant frequency pattern. For this purpose, machine learning algorithms may be used, for example, that take into account the necessary parameters (e.g., spatial orientation and acceleration, and optionally, temperature and / or pressure).
[0018] Although the processor and the fill level indicator are described as two independent units, it should be noted that they can also be embodied as a common unit that incorporates the functions of both units. Furthermore, at least one spatial orientation and acceleration sensor may be connected to the processor, and the processor may calculate a reference resonant frequency or reference resonant frequency pattern and pass those reference resonant frequencies to the fill level indicator. In such a configuration, the fill level indicator simply determines the actual fill level using the extracted resonant frequencies and reference resonant frequencies received from the processor.
[0019] After determining the current filling level of the container, the filling level indicator may output a corresponding filling level signal, which is then passed to, for example, an onboard computer or other control and monitoring system.
[0020] According to the embodiment, at least one spatial orientation and acceleration sensor includes a first sensor for measuring the pitch angle, a second sensor for measuring the yaw angle, a third sensor for measuring the roll angle of the container, and a fourth sensor for measuring acceleration along the pitch axis, yaw axis, and roll axis. Spatial orientation is defined with respect to the pitch angle, yaw angle, and roll angle.
[0021] Such spatial orientation and acceleration sensors are particularly advantageous in aircraft applications, especially if such sensors are already present in the aircraft. Therefore, signals from such sensors may be passed to a fill level monitoring device without the need to add additional sensors. However, at least one spatial orientation and acceleration sensor may be any position sensor suitable for determining the relative orientation of the fluid in the container with respect to the orientation of the container.
[0022] Furthermore, the fill level monitoring device may include an accelerometer, or, as described above, may use corresponding sensor data from a surrounding structure (e.g., an aircraft) to explain the change in resonant frequency captured by the acceleration. When such an accelerometer is used together with a spatial position sensor, the sensor measures six degrees of freedom, i.e., the spatial position with respect to each spatial axis and the corresponding acceleration with respect to each axis. In particular, when evaluating the fill level of a container by including an accelerometer, the superposition of gravity with such dynamic forces (e.g., forces captured by acceleration) may be considered.
[0023] According to another embodiment, at least one sensor is a device capable of measuring the dynamics of a container at the location of the sensor.
[0024] Such a device capable of measuring the dynamics of a container may be any device capable of detecting or measuring the characteristics of the container corresponding to the structural dynamics of the container (e.g., vibration or other suitable mechanical characteristics).
[0025] A device capable of measuring such characteristics may be, for example, a composite fiber strain gauge. Such a composite fiber strain gauge may consist of a rectangular piezoelectric ceramic rod sandwiched between an adhesive layer, electrodes, and a polyimide film. Electrodes are attached to the film in an interlocking pattern that transmits an applied voltage to and from the ribbon-shaped piezoelectric ceramic rod. This assembly is a sealed, durable package ready for use that enables in-plane poling, actuation, and detection. The composite fiber strain gauge can also be attached (usually bonded) as a thin surface conforming plate to various types of structures or incorporated into composite structures. When a voltage is applied, the composite fiber strain gauge acts as an actuator, bending or deforming the material, preventing vibration, or generating vibration. When no voltage is applied, the composite fiber strain gauge can act as a highly sensitive strain gauge that detects deformation, noise, and vibration. Thus, when the container vibrates or rocks, small deformations of the container are detected by the composite fiber strain gauge. Since the vibration of the container contains specific frequency components, the output signal of the composite fiber strain gauge follows the frequency pattern of the vibration.
[0026] According to another embodiment, at least one exciter is mounted on the container and configured to couple a vibration load corresponding to an input signal from a signal source to the container.
[0027] For this purpose, at least one exciter may be any device that can couple a vibration load or other mechanical load to the container. By way of non-limiting example, the exciter may be a piezoelectric element. Such piezoelectric elements are well known in the art. When a voltage is applied to such an element, the piezoelectric element deforms in response to an electrical signal (inverse piezoelectric effect). Thus, when an unsteady signal is applied, the piezoelectric element begins to vibrate in response to the frequency components of the input signal, thereby coupling the corresponding vibration load to the container. Such piezoelectric elements may be, for example, of the same type as the composite fiber strain gauges described above with respect to at least one sensor.
[0028] However, any other conceivable exciter may be used.
[0029] According to another embodiment, the signal source is configured to generate a signal suitable for obtaining a frequency response function (FRF) in a desired frequency range as an input signal.
[0030] Thus, the signal may be any signal that includes a frequency range necessary or desirable for monitoring the resonance frequency of the container suitable for obtaining a frequency response function, as described further below.
[0031] By way of non-limiting example, such a signal may be a white noise signal. As is known in the art, such a white noise signal is a statistically irregular signal having equal intensity at different frequencies. Thus, when such a white noise signal is used as the input signal, a wide range of evenly distributed frequency components are coupled to the container, and only the vibration at the current resonance frequency of the container exhibits a maximum amplitude. By using an appropriate window function (e.g., a Gaussian window or a rectangular window), the input signal may be restricted to a specific input frequency range.
[0032] However, any other input signal that includes the possible resonance frequencies of the container at different fill levels may be used.
[0033] According to another embodiment, the processor is configured to compare the vibration signal with the input signal by calculating the Fast Fourier Transform (FFT) of the vibration signal and the input signal, and comparing the FFT of the vibration signal with the FFT of the input signal.
[0034] However, as will be readily apparent to those skilled in the art, other spectral or modal analysis algorithms may be used.
[0035] According to another embodiment, the processor is configured to extract the resonant frequency by calculating the frequency response function (FRF) of the vibration signal with respect to the input signal using the FFT of the vibration signal and the FFT of the input signal, thereby obtaining a pattern of resonant frequencies.
[0036] We define such a frequency response function as follows.
number
[0037] According to another embodiment, the filling level indicator is configured to determine the current filling level of a container based on the extraction resonance frequency by correlating the acquisition pattern of the resonance frequency with the calibration pattern of the resonance frequency.
[0038] Although it is described that the resonant frequency is determined by correlating the acquisition pattern with the calibration pattern, the filling level may also be determined by tracking a single resonant frequency (in particular, a resonant frequency that shows a strong correlation with the filling level) over time. Such a single resonant frequency may be proportional to the filling level over a given time.
[0039] The calibration pattern may be determined, for example, by controlled discharge of the container in a laboratory or operating environment, thereby determining the resonant frequency pattern of the container for different fill levels and different spatial orientations. The resonant frequencies thus determined may be stored in a matrix, for example, one-dimensional or multi-dimensional. For example, such a matrix may be four-dimensional when using three spatial orientation sensors (for example, yaw, pitch, and roll). One dimension of the matrix may correspond to the fill level, the second dimension to yaw, the third dimension to pitch, and the fourth dimension to roll. The fill level of the container may then be determined by correlating the extracted reference frequency with the corresponding matrix element, taking into account the estimated spatial orientation of the fluid in the container during operation.
[0040] According to another embodiment, the filling level monitoring device is configured to determine the current filling level of a container based on the extracted resonant frequency or FRF by machine learning and artificial intelligence methods that are trained on the resonant frequency calibration pattern or FRF and use the resonant frequency acquisition pattern or FRF as input.
[0041] According to another embodiment, the resonant frequency calibration pattern or FRF includes resonant frequency calibration patterns or FRF for different spatial orientations of the fluid in the container. The fill level indicator is configured to be trained by machine learning and artificial intelligence methods with resonant frequency calibration patterns or FRF and resonant frequency acquisition patterns or FRF as inputs to select a resonant frequency calibration pattern corresponding to the current spatial orientation of the fluid in the container before determining the current fill level of the container.
[0042] According to another embodiment, the resonant frequency calibration pattern includes resonant frequency calibration patterns for different spatial orientations of the fluid in the container, and the filling level indicator is configured to select a resonant frequency calibration pattern corresponding to the current spatial orientation of the fluid in the container before determining the current filling level of the container.
[0043] However, instead of using stored reference data (e.g., calibration patterns), the corresponding reference data may be calculated "on the fly" by using a computer model of the structural dynamics of the vessel or other means. For example, the selected mode may be tracked over time, or an artificial intelligence-based algorithm (e.g., a machine learning algorithm) may be used.
[0044] According to a second embodiment, a hydrogen tank is provided. The hydrogen tank includes a container for holding liquefied hydrogen and a filling level monitoring device.
[0045] The filling level monitoring device may be embodied according to any one of the embodiments described above and is configured to monitor the filling level of the hydrogen tank container according to the principle described above.
[0046] According to a third aspect, an aircraft is provided. The aircraft includes an aircraft fuselage, an aircraft turbine, and a hydrogen tank. The hydrogen tank is fixed in place to the aircraft fuselage. At least one spatial orientation and acceleration sensor is a spatial orientation and acceleration sensor of the aircraft itself.
[0047] Such aircraft may use hydrogen as an alternative fuel, that is, they may use hydrogen as an energy source to drive a turbine. For example, hydrogen may be used as a primary energy source by directly burning it in the turbine, or hydrogen may be used as a secondary energy source by generating electrical energy using a hydrogen fuel cell and supplying power to the turbine with the electrical energy thus generated.
[0048] The fill level monitoring device according to this disclosure enables accurate monitoring of the fill level of a hydrogen tank under any flight conditions. By fixing the hydrogen tank to the fuselage, the spatial orientation of the liquid hydrogen in the tank may be determined relative to the tank's orientation using the aircraft's spatial orientation and acceleration sensors (e.g., pitch, yaw, and roll axis sensors). The hydrogen tank container may be positioned within the fuselage, for example, such that the longitudinal axis of the container coincides with the longitudinal axis of the fuselage. In this way, the pitch movement of the aircraft corresponds to the "pitch" movement of the container, etc. Therefore, the aircraft's coordinate system may be used directly for the container.
[0049] According to one embodiment, the filling level monitoring device is configured to monitor the hydrogen filling level of a container.
[0050] In particular, a fill level monitoring device may continuously monitor the fill level during flight and report the corresponding fill level to the pilot.
[0051] According to one embodiment, a suitable source of vibration within an aircraft for exciting a container in a desired frequency range is a signal source for a filling level monitoring device.
[0052] Such a vibration source may be any vibration source within the aircraft. The vibrations of such a vibration source may be coupled to a container and may function as an excitation source for a fill level monitoring device.
[0053] In another embodiment, the source of vibrations inside the aircraft is the aircraft turbine.
[0054] During operation, an aircraft turbine generates specific frequency components in the form of vibrations or electromagnetic noise. These noise or vibration signals may include a frequency range broad enough to encompass the resonant frequency range of the hydrogen tank container for different fill levels, thus eliminating the need for additional signal sources. Alternatively, the turbine vibrations may be directly coupled to the container, or the electromagnetic noise may be collected and transmitted to at least one exciter, for example, by using an antenna or other signal acquisition technique. In the first case, no additional exciter or additional signal source is required. In the second case, only an exciter is required, and no additional signal source is needed. However, it should be noted that an aircraft turbine is only one example of a vibration source that can be used in a fill level monitoring system, and any vibration source within the aircraft can be used as an excitation source for determining the fill level of the container. Therefore, the vibration source is not limited to an aircraft turbine.
[0055] In short, this disclosure provides an accurate monitoring system for tracking the fill level of a fluid tank (e.g., a liquid hydrogen tank). Due to the changing flight conditions of an aircraft (and the low-temperature properties of LiH2), conventional fill level monitoring techniques, such as measuring the fluid flowing out of the tank or determining the weight of the tank, are inherently inaccurate. These inaccuracies can be avoided by measuring the fill level of a fluid tank by monitoring the tank's fill level-dependent resonant frequency, and by further considering the spatial orientation of the fluid in the tank, especially during changing flight conditions (e.g., climbing or descending flight). Thus, this disclosure generally enables more accurate non-intrusion monitoring of the fill level of a fluid tank, thereby enhancing the safety of aircraft using alternative fuels (e.g., hydrogen).
[0056] While this disclosure describes aircraft applications, it should be noted that the disclosure can be used for any appropriate application (e.g., automotive and similar applications).
[0057] The following describes examples of embodiments in more detail with reference to the attached drawings. The examples are schematic and not proportional to the actual size. Identical reference numerals mean the same or similar elements. [Brief explanation of the drawing]
[0058] [Figure 1] This is a schematic diagram of a hydrogen tank equipped with a fill level monitoring device. [Figure 2] This is an example of a frequency response function determined for different filling levels in a fluid liquid tank container. [Figure 3] This is a schematic diagram of an aircraft that includes a hydrogen tank with a fill level monitoring device. [Modes for carrying out the invention]
[0059] Figure 1 schematically shows an example of an embodiment of a liquid hydrogen tank, with the overall dimensions shown as 300. The hydrogen tank 300 includes a container, with the overall dimensions shown as 200, and a fill level monitoring device, with the overall dimensions shown as 100. In the illustrated configuration, the fill level monitoring device 100 includes one or more (e.g., two or more) exciters 10 and one or more (e.g., eight or more) sensors 20. Furthermore, the fill level monitoring device 100 includes a signal source 30, a processor 40, a fill level indicator 50, and a spatial orientation and acceleration sensor 60. The exciters 10 are electrically connected to the signal source 30. The processor 40 is electrically connected to the fill level indicator 50. The signal source 30 is electrically connected to the processor 40, the sensors 20 are electrically connected to the processor 40, and the spatial orientation and acceleration sensor 60 are electrically connected to the fill level indicator 50.
[0060] Container 200 contains liquid hydrogen, and the level of liquid hydrogen filling is schematically indicated by the filling level 210. Container 200 is a pressure-resistant gas container configured to hold pressurized liquefied hydrogen gas.
[0061] As described elsewhere here, the signal source 30 may be any signal source that generates an electrical signal containing a number of frequency components. The frequency range over which the signal source 30 can generate one or more input signals extends to the possible resonant frequencies of the container 200 at different filling levels 210. Here, this frequency span of the resonant frequencies of the container 200 based on the liquefied hydrogen filling level 210 may be determined, for example, by computer simulation of the structural dynamics of the container 200. Alternatively, the frequency span may be determined in advance in a laboratory environment for ease of determination. In the illustrated configuration, the signal source 30 is a Gaussian white noise signal source 30 configured to generate a wide range of uniformly distributed frequency components.
[0062] The container 200 has various resonant frequencies, some of which are simply correlated with the structural dynamics of the container 200 itself, while other resonant frequencies depend on the filling level 210. In particular, some of the resonant frequencies are proportional to the filling level 210 of the container 200 and shift when the filling level 210 inside the container 200 changes. Therefore, the filling level 210 of the container 200 can be accurately determined by monitoring the shift in the resonant frequency of the container 200.
[0063] The Gaussian white noise signal source 30 is configured to generate a corresponding electrical signal or input signal 31 that is transmitted to the exciter 10. The exciter 10 may be any element or device capable of generating mechanical oscillations or vibrations. In the illustrated configuration, for example, the exciter 10 is a piezoelectric element directly mounted on the container 200 and using the inverse piezoelectric effect, thereby generating vibrations corresponding to the input signal 31 from the signal source 30 coupled to the container 200 by the exciter 10. However, the exciter 10 may be any other device capable of coupling mechanical vibrations to the container 200, and in particular, may not be directly mounted to the container 200. For example, the exciter 10 may be a sound wave source directed towards the container 200. However, the above description of the exciter 10 is merely an example, and in principle, any other suitable device may be used as the exciter 10.
[0064] During measurement, the oscillation or vibration from the exciter 10 corresponding to the resonant frequency of the container 200 relative to the filling level 210 is amplified within the container 200, generating the corresponding vibration within the container 200, while other frequency components are not amplified.
[0065] Next, the sensor 20 is configured to collect or measure these vibrations of the container 200 and generate a corresponding vibration signal 21 which is transmitted to the processor 40. The sensor 20 may be any sensor 20 capable of measuring oscillations or vibrations within the container 200. In the illustrated example of the embodiment, the sensor 20 is a composite fiber strain gauge consisting of an insulating flexible backing formed from a composite fiber material supporting a metal foil pattern. The gauge may be mounted on the container 200 (for example, using a suitable adhesive). When the container 200 vibrates or oscillates, small deformations of the container 200 deform the metal foil of the sensor 20, thereby changing the electrical resistance of the sensor 20. This change in resistance may be measured, for example, using a Wheatstone bridge. Since the vibrations of the container 200 contain specific frequency components, the change in the resistance of the fiber strain gauge follows the frequency pattern of the vibrations. However, other suitable sensors may be used. For example, the sensor 20 may be a piezoelectric element mounted on the container 200 (e.g., an exciter 10) that generates an electrical signal corresponding to a mechanical load coupled to the piezoelectric element from the container 200.
[0066] Although the diagram and description show two exciters 10 and eight sensors 20, it should be noted that any other quantities of exciters 10 and sensors 20 can be used depending on the specific requirements of the particular application. Generally, increasing the quantity of exciters 10 and sensors 20 increases the accuracy of filling level measurement because more data can be correlated.
[0067] The processor 40 may be any computing device that processes signals, such as a general-purpose computer having a CPU and memory components, a microcomputer, an FPGA, an ASIC, a TPU, or any combination thereof, or any other suitable computing device. The processor 40 receives the vibration signal 21 from the sensor 20 and further receives the input signal 31 from the signal source 30. By comparing the input signal 31 with the vibration signal 21, the processor 40 can extract the resonant frequency of the container 200 for the corresponding filling level 210. The processor 40 may perform spectral or modal analysis, for example, by calculating the Fast Fourier Transform (FFT) of the input signal 31 and the vibration signal 21. By comparing the obtained spectral functions, the resonant frequency may be easily extracted, as will be readily apparent to those skilled in the art. For example, the processor 40 may calculate a frequency response function (FRF) from the spectral functions of the input signal 31 and the vibration signal 21. Such a frequency response function is defined as follows:
number
[0068] In this equation, H(f) is the frequency response function representation for amplification of the amplitude of a specific frequency component over frequency f, V(f) is the vibration signal over frequency (e.g., the FFT of input signal 31), and I(f) is the input signal over frequency (e.g., the FFT of vibration signal 21). Since the vibration of the container 200 at the corresponding resonant frequency is amplified, the frequency response function H(f) thus obtained has a maximum at the resonant frequency. Figure 2 shows an example of such an example FRF, which will be described further later. The obtained frequency response function is transmitted to the filling level indicator 50.
[0069] The filling level indicator 50 determines the current filling level 210 of the container 200 by comparing the corresponding resonant frequency pattern known for the container 200 with the extracted resonant frequency (e.g., FRF from the processor 40) for different filling levels 210. The filling level indicator 50 may have, for example, a memory lookup table of frequency response functions or resonant frequency patterns for different filling levels 210. The current filling level of the container 200 may be obtained by correlating the memory reference data with the determination FRF (or generally, the extracted resonant frequency).
[0070] Since the resonant frequency of container 200 also depends on the spatial orientation of the fluid inside container 200 relative to the spatial orientation of container 200, as described above, the spatial orientation and acceleration sensors 60 determine the spatial orientation of the fluid inside container 200 relative to the gravity vector and transmit the corresponding spatial orientation data to the filling level indicator 50. The filling level indicator 50 may use the spatial orientation data to select a corresponding reference resonant frequency pattern before comparing the extracted resonant frequency or resonant frequency pattern with the reference data. For example, the reference resonant frequency values may be stored in a multidimensional matrix as previously described elsewhere, and the filling level indicator 50 may select a corresponding value for the current spatial orientation from this matrix before determining the filling level 210.
[0071] Instead of using stored reference data, the filling level indicator 50 may calculate the corresponding reference value "on the fly" by using a computer model of the structural dynamics of the container 200.
[0072] After determining the current filling level 210 of the container 200, the filling level indicator 50 outputs a filling level signal 51 that can be transmitted, for example, to a control system or display device. In aircraft applications, the filling level signal may be transmitted to a flight control computer or display device in the aircraft's cockpit.
[0073] Figure 2 shows an example of a plot of the frequency response function as described in Figure 1, obtained during a continuous discharge test. In such a continuous discharge test, the container 200 of the hydrogen tank 300 is discharged using a controlled method, and the frequency response function is determined according to the principle described herein. Figure 2 shows different frequency response functions for different filling levels 210. It can be seen that the resonant frequency of the container 200 shifts with changes in the filling level 210 of the container 200. Resonant peaks for four different filling levels 210, namely 100%, 93%, 50%, and 0%, are shown. Such reference frequency response functions may be determined in advance for different spatial orientations of the fluid in the container 200. The filling level indicator 50 in Figure 1 may use such frequency response functions determined in a laboratory environment as reference data for determining the filling level 210. However, such reference data may also be calculated by a structural dynamics model as described above.
[0074] Figure 3 shows an example of an embodiment of an aircraft 400 having a fuselage 410 and two turbines 420. Furthermore, the aircraft includes, for example, a liquid hydrogen tank 300 as described above with respect to Figure 1. The hydrogen tank 300 serves as a fuel source for the turbines 420. The turbines 420 may directly burn hydrogen from the hydrogen tank 300 as a primary energy source, or they may be electric turbines using electrical energy generated by a fuel cell that consumes hydrogen from the hydrogen tank 300, for example.
[0075] In this embodiment, the vibrations of the turbine 420 are directly coupled to the container 200 of the hydrogen tank 300. Thus, the turbine 420 itself functions as an exciter 10 for the container 200, coupling its vibrations to the container 200.
[0076] Furthermore, the aircraft's own yaw, pitch, and roll sensors are connected to the fill level indicator 50 and function as spatial orientation and acceleration sensors 60 in Figure 1. The tank is then fixed in place within the fuselage 410. Thus, no additional spatial orientation and acceleration sensors (e.g., 60, see Figure 1) are required, and existing sensors within the aircraft 400 can be used. Moreover, since the turbine 420 itself functions as an exciter 10 for the fill level monitoring device 100 of the hydrogen tank 300, no additional exciter 10 is required.
[0077] By including the spatial orientation data of the container 200 in the fill level monitoring device 100, the fill level 210 of the hydrogen tank 300 can be accurately monitored, particularly during any flight conditions, in aircraft applications.
[0078] It should be noted that “comprising” or “including” does not exclude other elements or steps, and “one” or “a” does not exclude multiple elements or steps. Furthermore, it should be noted that features or steps described in relation to any of the embodiments described above may be used in combination with other features or steps of the other embodiments described above. Reference numerals in the claims should not be considered limiting.
[0079] The subject matter disclosed herein can be implemented in software or using software in combination with hardware and / or firmware. For example, at least a portion of the subject matter described herein can be implemented in software executed by a processor or processing unit or using such software. In one example of an implementation, the subject matter described herein can be implemented using a computer-readable medium having computer-executable instructions (stored in a computer-readable medium) that control the computer performing the steps when executed by a computer processor. Examples of computer-readable mediums suitable for implementing the subject matter described herein include non-temporary devices (e.g., disk memory devices, chip memory devices, programmable logic devices, and application-specific integrated circuits). Furthermore, a computer-readable medium for implementing the subject matter described herein can be installed on a single device or computing platform, or distributed across multiple devices or computing platforms.
[0080] At least one example of embodiments of the present invention is disclosed herein, but modifications, substitutions, and alternatives will be obvious to those skilled in the art and will be practicable without departing from the scope of this disclosure. This disclosure is intended to include any modifications or variations of the examples of embodiments. Furthermore, in this disclosure, the terms “comprise” or “comprising” do not exclude other elements or steps, the terms “a,” “an,” or “one” do not exclude multiples, and the term “or” means one or both. Furthermore, the described features or steps may be used in combination with other features or steps in any order unless otherwise suggested by the disclosure or context. By this means that this disclosure incorporates by reference the complete disclosure of any patent or application claiming interest or priority. [Explanation of symbols]
[0081] 10 exciter 20 sensors 21 Vibration signals 30 signal source 31 Input signal 40 processing units 50 Filling level indicator 51 Filling level signal 60 Spatial orientation and acceleration sensors 100 Filling Level Monitoring Devices 200 containers 210 Filling Level 300 hydrogen tanks 400 aircraft 410 Torso 420 Turbine
Claims
1. A filling level monitoring device (100) for monitoring the filling level (210) of fluid in a container (200), At least one exciter (10) and At least one sensor (20) and A signal source (30) connected to at least one of the exciters (10) and configured to generate an input signal (31) containing a large number of frequency components, Processor (40) and At least one spatial orientation and acceleration sensor (60), Filling level indicator (50) and Includes, The at least one spatial orientation and acceleration sensor (60) is connected to the filling level indicator (50) and is configured to measure the spatial orientation of the fluid in the container (200). The at least one sensor (20) is connected to the processor (40) and is configured to detect vibrations in the container (200), generate a vibration signal (21) corresponding to the detected vibrations based on the vibrations detected in the container (200), and transmit the vibration signal (21) to the processor (40). The processor (40) is configured to compare the vibration signal (21) with the input signal (31) and extract the resonant frequency. The aforementioned filling level indicator (50) The extracted resonant frequency is received from the processor (40), The spatial orientation of the fluid in the container (200) is received from at least one spatial orientation and acceleration sensor (60). The current filling level (210) of the container (200) is determined based on the extraction resonance frequency and the spatial orientation of the fluid within the container (200). It is structured in such a way. Filling level monitoring device (100).
2. The at least one spatial orientation and acceleration sensor (60) is, A first sensor configured to measure the pitch angle, A second sensor configured to measure the yaw angle, A third sensor configured to measure the roll angle, A fourth sensor configured to measure the acceleration in each spatial orientation axis of the container (200) and Includes, The filling level monitoring device (100) according to claim 1, wherein the spatial orientation is defined with respect to the pitch angle, the yaw angle, the roll angle, and the acceleration for each spatial orientation.
3. The filling level monitoring device (100) according to claim 1, wherein the at least one sensor (20) is configured to measure the vibration dynamics of the container (200) at the position of the at least one sensor (20).
4. The filling level monitoring device (100) according to claim 1, wherein the at least one exciter (10) is mounted on the container (200) and configured to couple a vibration load corresponding to the input signal (31) from the signal source (30) to the container (200).
5. The filling level monitoring device (100) according to claim 1, wherein the signal source (30) is configured to generate a signal suitable for obtaining a frequency response function (FRF) in a desired frequency range as the input signal (31).
6. The filling level monitoring device (100) according to claim 1, wherein the processor (40) is configured to calculate the fast Fourier transform (FFT) of the vibration signal (21) and the input signal (31), and compare the vibration signal (21) with the input signal (31) by comparing the FFT of the vibration signal (21) with the FFT of the input signal (31).
7. The filling level monitoring device (100) according to claim 6, wherein the processor (40) is configured to calculate the frequency response function (FRF) of the vibration signal (21) with respect to the input signal (31) using the FFT of the vibration signal (21) and the FFT of the input signal (31), and thereby extract the resonant frequency by obtaining a pattern of resonant frequencies.
8. The filling level indicator (50) is configured to determine the current filling level (210) of the container (200) based on the extracted resonant frequency or FRF by correlating the acquired pattern or FRF of the resonant frequency with a calibration pattern of the resonant frequency, as described in claim 7, for the filling level monitoring device (100).
9. The filling level indicator (50) is configured to determine the current filling level (210) of the container (200) based on the extracted resonant frequency or FRF by a machine learning and artificial intelligence method that is trained on a calibration pattern or FRF of the resonant frequency using the acquired pattern or FRF of the resonant frequency as input, according to claim 7.
10. The calibration pattern or FRF of the resonant frequency includes the calibration pattern or FRF of the resonant frequency for different spatial orientations of the fluid in the container (200), The filling level indicator (50) is configured to be trained by machine learning and artificial intelligence methods with the calibration pattern or FRF of the resonant frequency and the acquisition pattern or FRF of the resonant frequency as inputs, in order to select a calibration pattern of the resonant frequency corresponding to the current spatial orientation of the fluid in the container (200) before determining the current filling level (210) of the container (200), the filling level monitoring device (100) according to claim 8.
11. The calibration pattern or FRF of the resonant frequency includes the calibration pattern or FRF of the resonant frequency for different spatial orientations of the fluid in the container (200), The filling level monitoring device (100) according to claim 8, wherein the filling level indicator (50) is configured to select a calibration pattern or FRF of a resonant frequency corresponding to the current spatial orientation of the fluid in the container (200) before determining the current filling level (210) of the container (200).
12. A filling level monitoring device (100) according to claim 1, including a display, wherein the filling level indicator (50) is configured to transmit a filling level signal (51) to the display.
13. The filling level monitoring device (100) according to claim 1, wherein the filling level indicator (50) is configured to transmit a filling level signal (51) to the flight control computer of the aircraft (400).
14. A container (200) for holding liquefied hydrogen, A filling level monitoring device (100) according to at least one of claims 1 to 13 and A hydrogen tank (300) containing [the necessary components].
15. Aircraft fuselage (410) and Aircraft turbine (420) and A hydrogen tank (300) according to at least one claim 14 and Includes, The hydrogen tank (300) is fixed in an appropriate place to the aircraft fuselage (410), At least one spatial orientation and acceleration sensor (60) is a spatial orientation and acceleration sensor (60) of the aircraft (400) itself. Aircraft (400).
16. The aircraft (400) according to claim 15, wherein the filling level monitoring device (100) is configured to monitor the filling level (210) of liquefied hydrogen in the container.
17. The aircraft (400) according to claim 15, wherein the signal source (30) of the filling level monitoring device (100) is a source of vibration within the aircraft (400) suitable for use in exciting the container (200) in a desired frequency range.