Low-temperature medium metering system and method for offshore storage
By combining a capacitive level sensor and an accelerometer with a Kalman filter algorithm, the problem of inaccurate measurement of cryogenic media stored at sea was solved, and high-precision level measurement was achieved in cryogenic and marine environments.
Patent Information
- Application Number
- CN202511869646.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-11
- Publication Date
- 2026-02-06
AI Technical Summary
In existing technologies, when cryogenic media are stored at sea, the extremely low temperature and the marine environment can cause metering tools to deform, condense, or become blocked by ice. Furthermore, the sloshing caused by the marine environment can affect the accuracy of liquid level measurement.
A capacitive liquid level sensor and an accelerometer are combined with a Kalman filter algorithm. The liquid level height is measured through a coaxial cylindrical electrode structure, and the acceleration data is fused for correction to reduce the impact of surges and ocean currents.
It improves the accuracy of cryogenic medium measurement, reduces the deviation of liquid level measurement, and ensures the stability and accuracy of the liquid level sensor in cryogenic and marine environments.
Smart Images
Figure CN121474490A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of cryogenic medium metering technology, and in particular to a cryogenic medium metering system and method for marine storage. Background Technology
[0002] When cryogenic media are stored in tanks on ocean-going transport ships or offshore platforms, they are often in a mixed state of gas and liquid phases. In order to accurately measure the content of cryogenic media in the tank, it is usually necessary to measure the liquid level of the cryogenic media and calculate the volume of gaseous cryogenic media in the remaining space in the tank based on the liquid level, thereby obtaining the total amount of cryogenic media stored in the tank.
[0003] In existing technologies, differential pressure level gauges and float-type level gauges are used to measure the liquid level of cryogenic media in storage tanks. However, because cryogenic media (such as liquid hydrogen, liquid oxygen, and liquid nitrogen) are stored at extremely low temperatures, typically between -165°C and -20°C, these measuring tools are prone to shrinkage and deformation at low temperatures, and may even experience condensation or ice blockage, leading to significant deviations in the measurement results. Furthermore, wind, waves, and ocean currents in the marine environment can cause transport ships or offshore platforms to experience rolling, pitching, and heaving movements, resulting in nonlinear sloshing of the liquid within the storage tank, which also severely affects the accuracy of level measurement.
[0004] Therefore, there is an urgent need to develop a new technical solution to solve the above-mentioned technical problems. Summary of the Invention
[0005] This invention provides a cryogenic medium metering system and method for marine storage, which can improve the accuracy of cryogenic medium metering results.
[0006] In a first aspect, the present invention provides a cryogenic medium metering system for marine storage, comprising: Spherical storage tanks are used to store cryogenic media; A capacitive liquid level sensor includes an inner electrode and an outer electrode in a coaxial cylindrical structure. The outer electrode is attached and fixed to the inner wall of the storage tank, and the inner electrode is fixed inside the storage tank and coaxial with the outer electrode. An insulating layer is provided between the outer electrode and the inner electrode. The liquid level sensor is used to collect the liquid level height measurement values at the positions where the low temperature medium contacts the two side walls of the storage tank. An accelerometer is used to collect the lateral and longitudinal accelerations of the storage tank. The processor is electrically connected to the liquid level sensor and the acceleration sensor, respectively, and is used to perform Kalman filtering and fusion on the measured values of lateral acceleration, longitudinal acceleration and liquid level height to obtain the actual value of the liquid level height of the cryogenic medium at the position of the central axis perpendicular to the horizontal plane in the storage tank.
[0007] Secondly, the present invention provides a method for metering cryogenic media for marine storage, applied to the system described in the first aspect of the present invention, the method comprising: The capacitive liquid level sensor collects the liquid level height measurements at the locations where the cryogenic medium contacts the two side walls inside the tank. The lateral and longitudinal accelerations of the storage tank are collected by the accelerometer. The processor performs Kalman filtering and fusion on the measured values of lateral acceleration, longitudinal acceleration, and liquid level to obtain the actual value of the liquid level of the cryogenic medium at the central axis position perpendicular to the horizontal plane inside the storage tank.
[0008] This invention provides a cryogenic medium metering system and method for marine storage. By configuring a capacitive level sensor into a coaxial cylindrical structure, the liquid level height is calculated based on the capacitance of the internal electrodes in contact with both the gaseous and liquid cryogenic media, resulting in a relatively accurate liquid level measurement in cryogenic environments. A Kalman filter algorithm is used to fuse acceleration data from an accelerometer and liquid level data from the capacitive level sensor to correct the liquid level measurement, reducing the impact of surges or ocean currents on the liquid surface within the storage tank. Attached Figure Description
[0009] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0010] Figure 1 This is a schematic diagram of a cryogenic medium metering system for marine storage provided in an embodiment of the present invention; Figure 2 It is based on Figure 1 A schematic diagram of a capacitive liquid level sensor is shown.
[0011] Figure label: 1-Storage tank; 2-Liquid level sensor; 21 - External electrode; 22-Internal electrode; 3-Processor; 4-Baffle. Detailed Implementation
[0012] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.
[0013] Please refer to Figure 1-Figure 2 This invention provides a cryogenic medium metering system for marine storage, comprising: Spherical storage tank 1 is used to store cryogenic media; The capacitive liquid level sensor 2 includes an inner electrode 22 and an outer electrode 21 in a coaxial cylindrical structure. The outer electrode 21 is attached and fixed to the inner wall of the storage tank 1, and the inner electrode 22 is fixed inside the storage tank 1 and coaxial with the outer electrode 21. An insulating layer is provided between the outer electrode 21 and the inner electrode 22. The liquid level sensor 2 is used to collect the liquid level height measurement values at the positions where the low temperature medium is in contact with the two side walls inside the storage tank 1. An accelerometer (not shown in the figure) is used to collect the lateral and longitudinal accelerations of storage tank 1; The processor 3 is electrically connected to the liquid level sensor 2 and the acceleration sensor respectively. It is used to perform Kalman filtering and fusion on the measured values of lateral acceleration, longitudinal acceleration and liquid level height to obtain the actual value of the liquid level height of the cryogenic medium at the position of the central axis perpendicular to the horizontal plane in the storage tank 1.
[0014] The cryogenic medium metering system in this embodiment of the invention is applicable to the level measurement of cryogenic media stored in tank 1 of a marine transport ship, and also applicable to the level measurement of cryogenic media in tank 1 of a marine storage platform. Tank 1 is spherical, and a capacitive level sensor 2 is installed inside, including an outer electrode 21 and an inner electrode 22, with an insulating layer between them. The outer electrode 21 and the inner electrode 22 are coaxial cylindrical electrode structures. The outer electrode 21 is fixed to the tank wall, and the inner electrode 22 is isolated from the tank wall by a flexible support (to reduce the transmission of tank wall vibration). The distance between the two electrodes is ≤1mm, and the ratio of electrode width to distance is ≥100:1 (e.g., 100mm width, 1mm distance) to improve measurement sensitivity. The outer electrode 21 and the inner electrode 22 are made of zirconium oxynitride or Teflon, ensuring stable operation within a temperature range of -165℃ to 50℃ (the storage environment of the cryogenic medium). Specifically, the external electrode 21 is fixed to the tank wall using a detachable nut combined with a V-type packing seal structure, which facilitates maintenance and ensures reliable sealing. This cryogenic medium metering system also includes an accelerometer, preferably an integrated triaxial MEMS accelerometer. The accelerometer can be installed at the bottom of the storage tank 1, or an accelerometer from a transport ship or offshore platform can be used to monitor the roll and pitch accelerations of the ship or platform in real time. When the accelerometer is installed at the bottom of the storage tank 1, it can be mounted on a structural base with minimal tank vibration, aligned with the main current direction of the ship. The sampling frequency of the accelerometer is ≥1Hz, capable of capturing liquid level fluctuations caused by ship movement. The processor 3 fuses the lateral and longitudinal acceleration data collected by the accelerometer and the liquid level measurement data collected by the level sensor 2. The processor 3 is equipped with an IC low-pass filter with a cutoff frequency of 0.3Hz to suppress high-frequency noise. A Kalman filter algorithm is used to fuse the acceleration data and capacitance signal, dynamically correcting the liquid level value.
[0015] Specifically, based on the total capacitance value monitored by liquid level sensor 2 C The specific principle for obtaining the liquid level height measurement value is as follows: C = C l + C a , C l = e l S l / 4πkd , C a = e a S a / 4πkd , C lLet be the first capacitance value corresponding to the liquid cryogenic medium in storage tank 1, and let be the second capacitance value corresponding to the gaseous cryogenic medium in storage tank 1. C a , e l The dielectric constant of a liquid cryogenic medium. e a The dielectric constant of a gaseous, low-temperature medium. k Boltzmann's constant, d The distance between the outer electrode 21 and the inner electrode 22. S l The first effective area of the liquid cryogenic medium in contact with the liquid level sensor 2 is [area missing]. S a This refers to the second effective area where the gaseous cryogenic medium contacts the liquid level sensor 2. Based on the first effective area... S l The radius r of the cylindrical structure corresponding to the inner electrode 22 and the width m of the capacitor plate are used to obtain the liquid level height measurement value of the cryogenic medium. h l = S l / 2πrm .
[0016] Because ships in the marine environment are affected by external forces such as wind, waves, and ocean currents, the tanks experience rolling, pitching, and heaving movements, which in turn cause nonlinear sloshing of the liquid inside. This sloshing results in large fluctuations in the liquid surface, such as standing waves, hydrocliff waves, and three-dimensional rotating waves, severely affecting the accuracy of liquid level measurement. Therefore, it is necessary to predict the wave shape of the liquid surface in tank 1 by monitoring the motion of the ship or offshore platform using an accelerometer, thereby correcting the liquid level height measurement value obtained by the liquid level sensor 2. Based on lateral acceleration... a x (t) and longitudinal acceleration a y (t) The roll angle of storage tank 1 is obtained. i (t) = arcsin(a x (t) / g) and pitch angle , t Indicates time, g The acceleration due to gravity is used; based on the measured liquid level, the irregular wave shape generated on the surface of the cryogenic liquid medium in tank 1 under shaking conditions is represented by a liquid surface wave function. g 罐内 =ω 1 g 1 +oh 2 g 2 +……+oh i g i ,in, oh 1 、oh 2 、……oh i For weight values, g 1 ,g 2 、…… g i The function is a predefined regular wave function; based on the measured variable at the previous time step, the prior estimate at the current time step is predicted. ,in, The prior estimate for the current moment. The variable to be measured at the previous moment, F The state transition matrix is used to update the error covariance matrix. ,in, P k Let be the error covariance matrix at the current time. F Here is the state transition matrix. P k-1 The error covariance matrix at the previous time step. Q The process noise covariance matrix is given; based on the error covariance matrix, the Kalman filter gain is obtained. ,in, K For Kalman filter gain, H This is a measurement matrix, used to represent the relationship between measured values and predicted state variables. R The noise covariance matrix is used; the optimal state estimate at the current moment is obtained based on the difference between the measured value and the prior state estimate. , z k The time history data of the movement of storage tank 1 is used; the error covariance matrix is updated again. ,in, H For the measurement matrix, R The noise covariance matrix is... I The identity matrix is used; the optimal weight values and corresponding liquid surface wave functions are obtained based on the optimal state estimation values. Actual liquid level height = measured liquid level height + (y 1 +y 2 ) / 2 , y 1 and y 2 are the curves corresponding to the liquid surface wave function and the ordinate values of the two side wall corners of tank 1, respectively.
[0017] In one embodiment of the present invention, it further includes: Two baffles 4 are respectively parallel to the central axis of the storage tank 1 that is perpendicular to the horizontal plane, and are symmetrically arranged on the two side walls of the storage tank 1, and located inside the liquid level sensor 2.
[0018] In this embodiment, two baffles 4 are respectively set on the side wall of the storage tank 1, and the distance between the two baffles 4 and the sensor is ≥20mm, which can reduce the impact of liquid sloshing on the sensor.
[0019] In one embodiment of the present invention, the baffle 4 is a conical structure. The bottom surface of the conical structure is located on the side away from the inner wall of the storage tank 1. The bottom surface is parallel to the central axis perpendicular to the horizontal plane. Multiple through holes are provided on the side of the conical structure to allow the low temperature medium to pass through.
[0020] In this embodiment, the baffle 4 is connected to the inner wall of the tank by a T-ring or reinforcing rib, with a thickness of 14mm, and has small holes with a diameter of φ14mm, spaced at 20mm intervals (opening rate 44.4%), and the small holes are arranged in a corner triangle.
[0021] In one embodiment of the present invention, it further includes: A temperature sensor, electrically connected to processor 3, is used to monitor the side wall temperature of storage tank 1.
[0022] In this embodiment, the side wall temperature of storage tank 1 is collected by a temperature sensor to establish a preset temperature compensation model, which corrects the influence of changes in the dielectric constant of the low-temperature medium in real time, avoiding measurement errors caused by temperature fluctuations. It is understood that the measurement principle of the liquid level sensor 2 in this embodiment is as follows: the capacitance value measured by the liquid level sensor 2 is converted into liquid level height. This conversion involves the dielectric constant of the low-temperature medium, which changes with temperature. Therefore, the dielectric constant needs to be corrected in real time using the side wall temperature of storage tank 1 to ensure the accuracy of the liquid level height value.
[0023] Furthermore, this invention provides a hydrogen metering method for maritime transportation, applied to a cryogenic medium metering system for marine storage, the method comprising: The liquid level height at the contact points between the cryogenic medium and the two side walls inside the tank is measured using a capacitive liquid level sensor. The lateral and longitudinal accelerations of the storage tank are collected using accelerometers. The processor performs Kalman filtering and fusion on the measured values of lateral acceleration, longitudinal acceleration, and liquid level height to obtain the actual value of the liquid level height of the cryogenic medium at the central axis position perpendicular to the horizontal plane inside the storage tank.
[0024] In one embodiment of the present invention, a capacitive liquid level sensor is used to collect liquid level measurements at locations where the cryogenic medium contacts two side walls inside the storage tank, including: Based on the total capacitance value monitored by the liquid level sensor C The first effective area of contact between the cryogenic liquid medium in the storage tank and the level sensor is obtained by the following formula.S l The second effective area of the gaseous cryogenic medium in contact with the liquid level sensor S a : C = C l + C a , C l = e l S l / 4πkd , C a = e a S a / 4πkd , C l Here, represents the first capacitance value corresponding to the liquid cryogenic medium inside the storage tank, and represents the second capacitance value corresponding to the gaseous cryogenic medium inside the storage tank. C a , e l The dielectric constant of a liquid cryogenic medium. e a The dielectric constant of a gaseous, low-temperature medium. k Boltzmann's constant, d This is the distance between the outer electrode and the inner electrode; Based on the first effective area S l The radius r of the cylindrical structure corresponding to the internal electrode and the width m of the capacitor plate are used to obtain the liquid level height measurement value of the cryogenic medium using the following formula. h l : h l = S l / 2πrm .
[0025] In one embodiment of the present invention, the processor performs Kalman filtering and fusion on the measured values of lateral acceleration, longitudinal acceleration, and liquid level height to obtain the actual value of the liquid level height of the cryogenic medium at the central axis position perpendicular to the horizontal plane inside the storage tank, including: Based on lateral acceleration a x (t) and longitudinal acceleration a y (t) The yaw angle of the storage tank is obtained. θ(t) = arcsin(a x (t) / g) and pitch angle , t Indicates time, g It is the acceleration due to gravity; Based on the measured liquid level, the irregular wave shape generated on the surface of the cryogenic liquid medium in the storage tank under agitation is represented as a liquid surface wave function. g 罐内 =ω 1 g 1 +oh 2 g 2 +……+oh i g i ,in, oh 1 、oh 2 、……oh i For weight values, g 1 ,g 2 、……g i This is a preset regular wave function; The roll angle, pitch angle, and weight values are used together as the variables to be measured in the Kalman filter. Based on the update iteration of the Kalman filter, the liquid surface wave function corresponding to the optimal weight value is obtained. The actual liquid level height is obtained based on the liquid surface wave function.
[0026] In one embodiment of the present invention, the roll angle, pitch angle, and weight value are used together as the variables to be measured in the Kalman filter. Based on the update iteration of the Kalman filter, the liquid surface wave function corresponding to the optimal weight value is obtained, including: Predict the prior estimate of the variable to be measured at the previous time step. ,in, The prior estimate for the current moment. The variable to be measured at the previous moment, F This is the state transition matrix; Update error covariance matrix ,in, P k Let be the error covariance matrix at the current time. F Here is the state transition matrix. P k-1 The error covariance matrix at the previous time step. Q The process noise covariance matrix; The Kalman filter gain is obtained based on the error covariance matrix. ,in, K For Kalman filter gain, HThis is a measurement matrix, used to represent the relationship between measured values and predicted state variables. R Here is the noise covariance matrix; Based on the difference between the measured value and the prior state estimate, the optimal state estimate at the current moment is obtained. , z k This is the time-history data of the storage tank's movement; Update the error covariance matrix again ,in, H For the measurement matrix, R The noise covariance matrix is... I It is the identity matrix; The optimal weight value and the corresponding liquid surface wave function are obtained based on the optimal state estimate.
[0027] In one embodiment of the present invention, obtaining the actual value of the liquid level height based on the liquid surface wave function includes: Actual liquid level height = Measured liquid level height + (y 1 +y 2 ) / 2 , y 1 and y 2 are the curves corresponding to the liquid surface wave function and the ordinate values of the two side wall corners of the storage tank, respectively.
[0028] In one embodiment of the present invention, it further includes: The dielectric constant of the liquid cryogenic medium is determined by monitoring the sidewall temperature of the storage tank using temperature sensors. e l Dielectric constant of gaseous cryogenic media e a .
[0029] It is understood that the method embodiments and system embodiments provided by the present invention are based on the same inventive concept and have the same beneficial effects. The beneficial effects of the method embodiments will not be elaborated here.
[0030] In summary, this invention provides a cryogenic medium metering system and method for marine storage. By configuring a capacitive level sensor as a coaxial cylindrical structure, the liquid level height is calculated based on the capacitance of the internal electrodes in contact with both the gaseous and liquid cryogenic media, resulting in a relatively accurate liquid level measurement in cryogenic environments. A Kalman filter algorithm is used to fuse acceleration data from an accelerometer and liquid level data from the capacitive level sensor to correct the liquid level measurement, reducing the impact of surges or ocean currents on the liquid level in the storage tank. Simultaneously, a baffle is designed to mitigate the impact of surges on the level sensor, preventing damage and providing technical support for the safe operation and level management of liquid hydrogen tanker transport vessels.
[0031] It should be noted that, in this invention, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.
[0032] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.
Claims
1. A cryogenic medium metering system for marine storage, characterized in that, include: Spherical storage tanks are used to store cryogenic media; A capacitive liquid level sensor includes an inner electrode and an outer electrode in a coaxial cylindrical structure. The outer electrode is attached and fixed to the inner wall of the storage tank, and the inner electrode is fixed inside the storage tank and coaxial with the outer electrode. An insulating layer is provided between the outer electrode and the inner electrode. The liquid level sensor is used to collect the liquid level height measurement values at the positions where the low temperature medium contacts the two side walls of the storage tank. An accelerometer is used to collect the lateral and longitudinal accelerations of the storage tank. The processor is electrically connected to the liquid level sensor and the acceleration sensor, respectively, and is used to perform Kalman filtering and fusion on the measured values of lateral acceleration, longitudinal acceleration and liquid level height to obtain the actual value of the liquid level height of the cryogenic medium at the position of the central axis perpendicular to the horizontal plane in the storage tank.
2. The system according to claim 1, characterized in that, Also includes: Two baffles are symmetrically arranged on the two side walls of the storage tank, parallel to the central axis perpendicular to the horizontal plane, and located inside the liquid level sensor.
3. The system according to claim 2, characterized in that, The baffle is a conical structure, with the bottom surface of the conical structure located away from the inner wall of the storage tank. The bottom surface is parallel to the central axis perpendicular to the horizontal plane, and the side surface of the conical structure is provided with multiple through holes that allow the cryogenic medium to pass through.
4. The system according to claim 1, characterized in that, Also includes: A temperature sensor, electrically connected to the processor, is used to monitor the sidewall temperature of the storage tank.
5. A method for metering cryogenic media for marine storage, characterized in that, Applied to the system according to any one of claims 1-4, the method comprises: The capacitive liquid level sensor collects the liquid level height measurements at the locations where the cryogenic medium contacts the two side walls inside the tank. The lateral and longitudinal accelerations of the storage tank are collected by the accelerometer. The processor performs Kalman filtering and fusion on the measured values of lateral acceleration, longitudinal acceleration, and liquid level to obtain the actual value of the liquid level of the cryogenic medium at the central axis position perpendicular to the horizontal plane inside the storage tank.
6. The method according to claim 5, characterized in that, The step of acquiring liquid level measurements at the locations where the cryogenic medium contacts the two side walls of the storage tank using the capacitive liquid level sensor includes: Based on the total capacitance value monitored by the liquid level sensor C The first effective area of contact between the cryogenic liquid medium in the storage tank and the liquid level sensor is obtained by the following formula. S l The second effective area of the gaseous cryogenic medium in contact with the liquid level sensor S a : C = C l + C a ， C l = ε l S l / 4πkd ， C a = ε a S a / 4πkd ， C l Let be the first capacitance value corresponding to the liquid cryogenic medium inside the storage tank, and let be the second capacitance value corresponding to the gaseous cryogenic medium inside the storage tank. C a , ε l The dielectric constant of a liquid cryogenic medium. ε a The dielectric constant of a gaseous, low-temperature medium. k Boltzmann's constant, d This is the distance between the outer electrode and the inner electrode; Based on the first effective area S l The radius r of the cylindrical structure corresponding to the inner electrode and the width m of the capacitor plate are used to obtain the measured value of the liquid level height of the cryogenic medium using the following formula. h l : h l = S l / 2πrm 。 7. The method according to claim 6, characterized in that, The step of fusing the measured values of lateral acceleration, longitudinal acceleration, and liquid level height using Kalman filtering by the processor to obtain the actual liquid level height of the cryogenic medium at the central axis position perpendicular to the horizontal plane within the storage tank includes: Based on the lateral acceleration a x (t) and longitudinal acceleration a y (t) The roll angle of the storage tank is obtained. θ(t) = arcsin (a x (t) / g) and pitch angle , t Indicates time, g It is the acceleration due to gravity; Based on the measured liquid level, the irregular wave shape generated on the surface of the cryogenic liquid medium in the storage tank under shaking conditions is represented as a liquid surface wave function. ζ 罐内 =ω 1 ζ 1 +ω 2 ζ 2 +……+ω i ζ i ,in, ω 1 ω 2 、……ω i For weight values, ζ 1 ζ 2 、……ζ i This is a preset regular wave function; The roll angle, the pitch angle, and the weight value are used together as the variables to be measured in the Kalman filter. Based on the update iteration of the Kalman filter, the liquid surface wave function corresponding to the optimal weight value is obtained. The actual value of the liquid level height is obtained based on the liquid surface wave function.
8. The method according to claim 7, characterized in that, The step of using the roll angle, pitch angle, and weight value as the test variables for Kalman filtering, and obtaining the liquid surface wave function corresponding to the optimal weight value based on the Kalman filter update iteration, includes: Predict the prior estimate of the variable to be measured at the previous time step. ,in, The prior estimate for the current moment. The variable to be measured at the previous time step, F This is the state transition matrix; Update error covariance matrix ,in, P k Let be the error covariance matrix at the current time. F Here is the state transition matrix. P k-1 Let be the error covariance matrix of the previous time step. Q The process noise covariance matrix; The Kalman filter gain is obtained based on the error covariance matrix. ,in, K For Kalman filter gain, H This is a measurement matrix, used to represent the relationship between measured values and predicted state variables. R Here is the noise covariance matrix; Based on the difference between the measured value and the prior state estimate, the optimal state estimate at the current moment is obtained. , z k This refers to the time-history data of the movement of the storage tank; Update the error covariance matrix again ,in, H For the measurement matrix, R The noise covariance matrix is... I It is the identity matrix; The optimal weight value and the corresponding liquid surface wave function are obtained based on the optimal state estimate.
9. The method according to claim 8, characterized in that, The process of obtaining the actual value of the liquid level height based on the liquid surface wave function includes: Actual liquid level height = Measured liquid level height + (y 1 +y 2 ) / 2 , y 1 and y 2 represents the curve corresponding to the liquid surface wave function and the ordinate values of the two side wall corners of the storage tank.
10. The method according to claim 6, characterized in that, Also includes: The sidewall temperature of the storage tank is monitored by a temperature sensor, and the dielectric constant of the liquid cryogenic medium is determined based on the sidewall temperature. ε l Dielectric constant of gaseous cryogenic media ε a .