POWERBUS-based differential pressure type static leveling instrument and liquid level correction algorithm

Abstract

The invention discloses a differential pressure type static force level gauge which comprises a liquid storage cavity and a circuit cavity which are fixedly connected, a through hole is formed between the liquid storage cavity and the circuit cavity, and a circuit unit is arranged in the through hole. The system is characterized in that the circuit unit comprises an MCU module, and a temperature sensor module, a reference power supply module, a data storage chip, a POWERBUS communication module and a pressure sensor which are electrically connected with the MCU module; the number of parts of the static leveling instrument is greatly reduced, the complexity of the parts is greatly simplified, the structure is simple, and the manufacturing cost is low; the device has the advantages of low requirements on use sites, wide application range, high safety, simplicity in operation and high flexibility. The invention further discloses a liquid level correction algorithm which comprises the following steps: S1, collecting data; s2, filtering out a fluctuation value of the liquid level difference value; s3, constructing a relation model of the liquid level error and the temperature difference; s4, liquid level difference correction is carried out; according to the data obtained by the method, the measurement accuracy is improved.

Description

Technical Field

[0001] The invention relates to the field of differential pressure liquid level sensors, and in particular to a differential pressure static level gauge based on POWERBUS and a liquid level correction algorithm. Background Art

[0002] Static level is a kind of monitoring equipment widely used in engineering structures such as roadbed, dam, bridge, tunnel, etc. In practical application, a static level is installed at the reference point and the measured point respectively, and it is placed on a fixed horizontal base point. When the measuring point rises or falls relative to the reference point, each measuring point will produce pressure changes, so as to calculate the rise and fall changes of each measuring point relative to the horizontal base point. With the diversification of application fields and the increasing demand for monitoring, the requirements for the range, accuracy, size, adaptability and protection level of monitoring equipment are becoming increasingly stringent. At present, there are many types of static levels. After research, it is found that the existing static levels have the disadvantages of complex structure, small range, high damage rate, poor long-term stability, regular recalibration, high maintenance cost, fixed signal output form, and great influence of external environment (such as temperature). In addition, some sensors have high installation requirements, poor measurement accuracy and reliability defects. Summary of the invention

[0003] In order to solve the problems in the background technology, the present invention provides a pressure differential static level with simple structure, convenient use, low cost, high precision, wide application range, integration of liquid level correction algorithm and easy maintenance. The present invention also provides a liquid level correction algorithm that can increase the accuracy of measurement.

[0004] To this end, the present invention adopts the following technical solutions:

[0005] A pressure differential static level based on POWERBUS, comprising a liquid storage chamber and a circuit chamber that are fixedly connected, a through hole formed between the liquid storage chamber and the circuit chamber, a circuit unit arranged in the through hole, the liquid storage chambers and the circuit chambers between a plurality of the pressure differential static levels are respectively connected, the circuit unit comprises an MCU module and a temperature sensor module electrically connected thereto, a reference power supply module, a data storage chip, a POWERBUS communication module and a pressure sensor; POWERBUS communication interfaces are also arranged on both sides of the circuit chamber;

[0006] The MCU module is used to receive data from the temperature sensor module and the pressure sensor and store the data in the data storage chip after processing;

[0007] The reference power supply module is used to supply power to other components in the circuit unit;

[0008] The POWERBUS communication module is used to transmit data between the pressure differential static level gauges through the POWERBUS communication interface;

[0009] The circuit cavity is fixedly connected to the plane to be measured via a bottom plate fixedly connected to the circuit cavity.

[0010] Preferably, a transparent liquid observation window and a horizontal bubble groove are also provided on the top of the liquid storage cavity;

[0011] The liquid observation window is used to observe whether there are bubbles remaining inside the liquid storage cavity;

[0012] The level bubble groove is used to judge whether the pressure differential type static level is installed horizontally through the level bubble movably connected thereon.

[0013] A liquid level correction algorithm based on a pressure differential static level instrument comprises the following steps:

[0014] S1, data collection:

[0015] Use the temperature sensor module and the pressure sensor to collect a total of N liquid level height values ​​h(n) and temperature values ​​t(n), n∈[1,N], and n is a time point;

[0016] S2, the fluctuation value of the filtered liquid level difference:

[0017] Calculate the liquid level difference H(n) at adjacent time points, H(n) = h(n+1)-h(n), n≤N-1;

[0018] A fifth-order polynomial is used to fit the liquid level difference H(n) between the time point n and the adjacent time points, as shown in formula (1):

[0019] H(n)=I h +A1·n+A2n 2 +A3n 3 +A4n 4 +A5n 5 ; (1)

[0020] Among them, I h , A1, A2, A3, A4 and A5 are all constant terms;

[0021] Get the I h , A1, A2, A3, A4 and A5 are then brought back to formula (1), and then the time point n is brought in to calculate the corrected level difference H at adjacent time points ′ (n), (n≤N-1) relational model;

[0022] S3, construct the relationship model between liquid level error and temperature difference:

[0023] Calculate the temperature difference T(n) between adjacent time points, T(n) = t(n+1)-t(n), n≤N-1;

[0024] Use a fifth-order polynomial to fit the corrected liquid level difference H at adjacent time points ′ (n) and the temperature difference T(n) at adjacent time points, as shown in formula (2):

[0025] H′(n)=I t +B1·T(n)+B2T(n) 2 +B3T(n) 3 +B4T(n) 4 +B5T(n) 5 ; (2)

[0026] Among them, I t , B1, B2, B3, B4 and B5 are all constant terms;

[0027] Get I t , B1, B2, B3, B4 and B5, then return to formula (2) and replace H with D ′ (n), T replaces T(n), and the relationship model between liquid level error and temperature difference is obtained, which is formula (3):

[0028] D=I t +B1·T+B2T 2 +B3T 3 +B4T 4 +B5T 5 ; (3)

[0029] Where D represents the liquid level error caused by temperature change, and T represents the temperature difference at any time;

[0030] S4, perform liquid level difference correction:

[0031] After using the temperature sensor module and the pressure sensor to obtain the liquid level height value and the new temperature value at the collection time, the temperature difference between the collection time and the moment before the collection time is calculated and substituted into formula (3) to obtain the liquid level error at the collection time;

[0032] The corrected liquid level height value at the collection time is obtained by subtracting the liquid level error at the collection time from the liquid level height value at the collection time.

[0033] Preferably, the N times of collected data in S1 are collected and completed within one week.

[0034] Preferably, the liquid level height value and the temperature value are collected once every hour.

[0035] Preferably, S5 is further included to improve the model using a sliding window method:

[0036] The model is continuously fitted using the continuously acquired new liquid level height values ​​and temperature values, and the relationship model of the corrected liquid level difference at adjacent time points in S2 and the relationship model of the liquid level error and the temperature difference in S3 are continuously improved.

[0037] Preferably, any time in S3 is after the time of acquiring data N times in S1.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] 1. A liquid level correction algorithm is added to the MCU module of the differential pressure static level of the present invention, and the measurement error caused by temperature change is reduced by a high-order polynomial fitting algorithm. The data can be adaptively fitted and corrected by a sliding window, thereby improving the measurement accuracy.

[0040] 2. The differential pressure static level of the present invention adopts POWERBUS mode for communication, combining the power supply line and the signal line into one, thus avoiding wiring errors during construction.

[0041] 3. The number of parts and complexity of the differential pressure static level of the present invention are greatly simplified, the structure is simple, and the manufacturing cost is low.

[0042] 4. The differential pressure static level of the present invention uses a Huygens bridge pressure-sensitive element made of silicon pressure and an intelligent amplifier (ASIC) to achieve pressure sampling and conversion with high measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a schematic diagram of the three-dimensional structure of a pressure differential static level;

[0044] Figure 2 for Figure 1 A cross-sectional view of the left side view of a medium pressure differential static level;

[0045] Figure 3 for Figure 1 A cross-sectional view of the front view of a medium pressure differential static level;

[0046] Figure 4 for Figure 1 Schematic diagram of the overhead structure of the medium pressure differential static level;

[0047] Figure 5 This is a schematic diagram of the module composition of the pressure differential static level;

[0048] Figure 6 It is a curve chart comparing the level difference at adjacent time points of the pressure differential static level before and after correction;

[0049] Figure 7 It is the temperature value and liquid level height curve diagram of the pressure differential static level;

[0050] Figure 8 It is a curve diagram of temperature difference and liquid level difference at adjacent time points of a differential pressure static level;

[0051] Fig. 9 This is the relationship between the temperature difference and the liquid level difference at adjacent time points before fitting of the differential pressure static level;

[0052] Fig.10 This is the relationship between the temperature difference and the liquid level difference at adjacent time points after fitting of the differential pressure static level;

[0053] Fig.11 A curve diagram of liquid level values ​​measured by a pressure differential static level in an embodiment of the present invention;

[0054] Fig.12 A curve diagram of the change in liquid level difference before eliminating the temperature effect in an embodiment of the present invention;

[0055] Fig.13 It is a curve diagram of the change of liquid level difference after eliminating the temperature influence in the embodiment of the present invention.

[0056] In the figure:

[0057] 1. Liquid storage chamber, 2. Circuit chamber, 3. Bottom plate, 4. Liquid pipe interface, 5. Air pipe interface, 6. Mounting hole, 7. Exhaust hole 8. POWERBUS communication interface, 9. Liquid observation window, 10. Horizontal bubble tank, 11. MCU module, 12. Reference power module, 13. Temperature sensor module, 14. Pressure sensor, 15. POWERBUS communication module, 16. Communication indication module, 17. Power conversion module, 18. Data storage chip. DETAILED DESCRIPTION

[0058] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0059] Example 1

[0060] Figures 1 to 5 The embodiment of the differential pressure static level of the present invention is shown in the figure. As shown in the figure, the differential pressure static level comprises a liquid storage chamber 1 with a cylindrical shape, a circuit chamber 2 with a rectangular shape and a bottom plate 3.

[0061] The liquid storage chamber 1 is a hollow structure with an opening at the bottom. Two liquid pipe interfaces 4 are symmetrically provided on the side wall of the liquid storage chamber 1. The two liquid pipe interfaces 4 are connected to the liquid storage chambers of other pressure differential static level gauges through liquid pipes, so as to allow the liquid in the liquid storage chambers of multiple pressure differential static level gauges to circulate.

[0062] An exhaust hole 7 is provided on the side of the liquid storage chamber 1, and an exhaust screw is installed on the exhaust hole 7. When the exhaust screw is loosened, the bubbles in the liquid storage chamber 1 will be discharged, and the exhaust screw is tightened after the bubbles are discharged;

[0063] The circuit cavity 2 is a hollow structure with a hole at the top and an opening at the bottom;

[0064] Two air pipe interfaces 5 are symmetrically provided on the left and right sides of the circuit cavity 2. After the two air pipe interfaces 5 are connected to the circuit cavities of other differential pressure static level gauges, the gas in the circuit cavity can flow. The left and right sides of the circuit cavity 2 are also symmetrically provided with POWERBUS communication interfaces 8. The two POWERBUS communication interfaces 8 are used to connect other differential pressure static level gauges or a host computer, and are used for circuit connection and data transmission between multiple differential pressure static level gauges.

[0065] The top surface of the circuit cavity 2 is fixedly connected to the liquid storage cavity 1, and the bottom surface of the circuit cavity 2 is fixedly connected to the bottom plate 3; the opening on the top surface of the circuit cavity 2 is connected to the opening on the bottom surface of the liquid storage cavity 1, and the bottom plate 3 is used to close the opening on the bottom surface of the circuit cavity 2. The bottom plate 3 is also provided with a mounting hole 6, and the differential pressure static level is fixedly connected to the surface to be measured through the mounting hole 6 and screws thereon.

[0066] A transparent liquid observation window 9 is provided on the top surface of the liquid storage chamber 1 for observing whether there are bubbles in the liquid in the liquid storage chamber 1; a horizontal bubble groove 10 is also provided on the top surface of the liquid storage chamber 1 for placing a horizontal bubble to observe whether the pressure differential static level of the present invention is installed horizontally.

[0067] A circuit unit is arranged in the circuit cavity 2, and the circuit unit includes an MCU module 11, and a reference power module 12, a temperature sensor module 13, a pressure sensor 14, a POWERBUS communication module 15, a communication indication module 16, a power conversion module 17 and a data storage chip 18 electrically connected to the MCU module.

[0068] The reference power module 12 includes a precision reference chip MCP1525, which is used to convert a 5V voltage into a 2.5V voltage;

[0069] The temperature sensor module 13 includes an NTC temperature sensor and a sampling resistor, and is used to convert the temperature value at the measurement point into a voltage and input the voltage into the AD input terminal of the MCU module 11 .

[0070] The pressure sensor 14 is arranged between the circuit cavity 2 and the liquid storage cavity 1. The pressure sensor 14 forms a seal with the cavity of the liquid storage cavity 1, and is used to detect the change of liquid pressure in the liquid storage cavity 1, and convert the pressure value into voltage and send it to the AD input end of the MCU module 11.

[0071] The MCU module 11 includes STC15W4K56S4 and a crystal oscillator circuit to realize the functions of reference voltage input, temperature reading, pressure reading, POWERBUS communication, and communication indication.

[0072] The POWERBUS communication module 15 includes a communication chip PB331. The POWERBUS communication module 15 is connected to the POWERBUS communication interface 8 and is used to realize the communication function between the MCU and the MCU modules or host computers of other differential pressure hydrostatic level gauges. It can also be used to remotely update the program in the POWERBUS communication module 15.

[0073] The communication indication module 16 is mainly composed of a light emitting diode and a resistor, and realizes the indication function of the POWERBUS communication module 15 during communication.

[0074] The power conversion module 17 is used to convert the external input voltage into a 5V voltage and supply power to other circuits.

[0075] The data storage chip 18 is used to store the pressure data and temperature data received by the MCU module 11 .

[0076] The circuit unit also includes a parameter setting circuit and a photoelectric isolation circuit. The parameter setting circuit is used to set the communication ID number, zero point calibration and temperature correction of the static level; the photoelectric isolation circuit isolates the interference source and the parts susceptible to interference, so that the static level only maintains signal contact with the site without direct electrical contact, and has a good isolation effect on the input and output electrical signals.

[0077] When the pressure differential static level of the above structure is used for measurement, the pressure sensor 14 transmits the voltage signal to the MCU module for calculation and analysis, converts it into a digital signal and outputs it from the POWERBUS communication interface 8. After being configured by the host computer software, the POWERBUS communication interface 8 can be interconnected with other pressure differential static levels or acquisition terminals of the present invention, output digital quantity signals, and transmit the digital quantity signals to the acquisition terminal.

[0078] The POWERBUS bus communication adopted by the present invention improves the application of the traditional RS-485 bus to address the construction design defects, and the communication protocol complies with the Modbus communication protocol. In the POWERBUS bus communication, TDMA communication technology is adopted to combine the power line and the signal line into one, realizing the technology of sharing one bus for signal and power supply, avoiding wiring errors in construction, thereby simplifying the construction design. The data transmission and power supply mode of POWERBUS bus communication is as follows:

[0079] 1. Data transmission: POWERBUS bus transmits data serially on the same pair of wires. The process of sending or reading data from a master station to multiple slave stations usually adopts the Master-Slave mode. The master station sends an inquiry command to the slave station, and the slave station returns a response after receiving the command from the master station. This communication method relies on a specified communication protocol to ensure interoperability and operational safety between different devices;

[0080] 2. Power supply: The POWERBUS bus can provide power to field devices through the same pair of wires, which can reduce the number of cables and wiring costs and simplify the system installation process.

[0081] Compared with traditional RS-485 bus communication, POWERBUS bus has the following specific advantages:

[0082] 1. Unify power supply and data transmission, simplify wiring, and eliminate the need for electrical isolation, greatly reducing installation costs;

[0083] 2. Non-polarity wiring saves construction, installation and debugging time;

[0084] 3. It can realize long-distance communication and improve the reliability of information transmission;

[0085] 4. Flexible expansion capability, convenient for adding or reducing system equipment;

[0086] 5. Adopt digital communication mode, which has high anti-interference ability;

[0087] 6. The bus can provide 20A high current, and a single slave can provide 1A current;

[0088] 7. Low configuration, no requirements on load, no restrictions on current fluctuations;

[0089] 8. Flexible wiring, you can use any cable (twisted pair, BV cable), and can be mixed with 220V without separate conduit.

[0090] In the above-mentioned differential pressure static level, the pressure sensor 14 adopts a diffused silicon pressure sensor, which is placed between the circuit cavity and the liquid storage cavity. After the liquid storage cavity is filled with liquid, the liquid in the liquid storage cavity will pass through the diaphragm on the upper part of the pressure sensor, causing the diaphragm to produce a micro-displacement proportional to the medium pressure. The resistance value of the sensor changes, and the output pressure standard measurement signal is converted and input into the MCU module. The cable is then led out through the POWERBUS communication module and connected to other differential pressure static levels of the present invention or to the host computer. The bottom of the pressure sensor is connected to the circuit board storage place, and it needs to be connected to the atmosphere to make the pressure value stable.

[0091] During actual measurement, after fixing each differential pressure static level, first connect their air pipe interfaces and liquid pipe interfaces to each other in sequence, and then connect the communication cable through the POWERBUS communication interface. Because the POWERBUS communication method is used, there is no need to distinguish the line sequence, and only two wires are needed for power supply and communication.

[0092] Select a pressure differential static level with a stable and reliable position as the reference point, and the other pressure differential static levels as monitoring points. The reference point should not be affected by the construction and connected to the liquid storage tank through a liquid pipe. Open the water pipe of the farthest pressure differential static level, slowly add antifreeze to the liquid storage tank until all liquid pipes are filled with liquid, and then block the liquid pipe interface of the farthest pressure differential static level from the reference point.

[0093] For each differential pressure hydrostatic level, when bubbles are observed in the liquid observation window, you can loosen the screws because the bubbles are at the top and will be squeezed out first. After there are no bubbles, tighten the screws and finally use the level bubble to adjust all differential pressure hydrostatic levels to a horizontal level.

[0094] After all the differential pressure static levels are installed, wrap all the liquid pipes with thermal insulation cotton to reduce the errors caused by different temperature values ​​at each measuring point.

[0095] Embodiment 2

[0096] Since the entire pressure differential static level system will be affected by many factors such as the installation distance of the pressure differential static level at the reference point, the bending degree of the connecting water pipe, the liquid expansion coefficient and the on-site installation environment, it is necessary to comprehensively consider the error factors and add a liquid level correction algorithm to the circuit unit of the pressure differential static level of the present invention.

[0097] Because the location of the reference point, the degree of bending of the connecting water pipe, and the on-site installation environment are different in each project and are uncontrollable factors, this method excludes the data factors of the reference point, and through the analysis of the test data, it is found that the temperature difference and liquid level difference at adjacent time points have a strong negative correlation. The farther away from the reference point, the greater the impact of the temperature difference. The reason is that the farther away from the reference point, the greater the difference in environmental conditions between the two devices, and the more difficult it is for the connected liquid to reach a relatively balanced state, so the error of the liquid level difference affected by temperature can be used as a comprehensive error factor. The algorithm is fitted according to the relationship between the temperature difference and liquid level difference at adjacent time points.

[0098] The temperature sensor module and data storage chip are designed on the circuit board of the pressure differential static level. The current liquid level value and temperature value are obtained by collecting data from the pressure sensor and temperature sensor. In the case of collecting data once an hour, the liquid level value collected in a week can be stored in the data storage chip, and the data can be read by the MCU to perform fitting calculations using the embedded liquid level correction algorithm. After calculating the parameters of the data fitting formula, the data of the next frequency will continue to be stored in a loop to achieve the effect of data fitting correction.

[0099] After the pressure differential static level system composed of multiple pressure differential static levels is installed, each pressure differential static level can be calibrated by the following method; the following are the specific steps of the liquid level correction algorithm of the present invention:

[0100] S1, data collection:

[0101] For any differential pressure static level, collect the liquid level h(n) and temperature t(n) for N times in one week, n∈[1,N];

[0102] S2, the fluctuation value of the filtered liquid level difference:

[0103] Because the differential pressure static level uses a diffused silicon pressure sensor with an accuracy of 0.15%, the sensor will have numerical fluctuations within the accuracy range under the same environment. In order to avoid the impact of data fluctuations on the parameter fitting algorithm, the fluctuation value of the liquid level difference needs to be filtered out first. After multiple data analyses of the liquid level differences at adjacent time points, it was found that the fourth-order polynomial was underfitting and the sixth-order polynomial was overfitting, so the fifth-order polynomial was selected as the liquid level difference correction algorithm. The specific fitting formula is as follows:

[0104] H(n)=I h +A1·n+A2n 2 +A3n 3 +A4n 4 +A5n 5 ; (1)

[0105] Among them, H(n) is the liquid level difference at adjacent time points, H(n)=h(n+1)-h(n), n≤N-1, and the MCU module will automatically calculate the liquid level intercept I in the formula through a high-order polynomial fitting algorithm. h And the constant values ​​of A1, A2, A3, A4, and A5.

[0106] Get I h , A1, A2, A3, A4, A5 and then bring back the above formula to calculate H by n ′ (n) H ′ (n),n≤N-1,H ′ (n) is the corrected liquid level difference between adjacent time points.

[0107] Figure 6 This is a curve chart comparing the liquid level difference at adjacent time points of the pressure differential static level before and after correction. It can be clearly seen that the corrected liquid level difference eliminates the fluctuation value, making the data smoother while keeping the overall trend unchanged.

[0108] S3, construct the relationship model between liquid level error and temperature difference:

[0109] To eliminate the change in liquid level due to the change in ambient temperature, it is necessary to find the law of how the liquid level difference is affected by temperature change. Figure 7 and Figure 8 In the curves of temperature value and liquid level value, temperature difference and liquid level difference at adjacent time points, it is found that temperature value and liquid level value, temperature difference and liquid level difference are negatively correlated. Since each differential pressure static level is installed in a different position, the liquid level value may vary greatly, so its own temperature difference and liquid level difference are used for data fitting. The temperature difference at adjacent time points is sorted from small to large, with the temperature difference at adjacent time points as the horizontal axis, and the corrected liquid level difference H with the same n value ′ (n) is the vertical axis, and a scatter plot of the relationship between the two is made as follows Fig. 9 As shown, we can see that the greater the temperature difference, the smaller the liquid level difference, but the curve changes unevenly and it is impossible to determine the relationship formula between the two. Therefore, we need to find the relationship formula between the temperature difference and the liquid level difference while fitting the data.

[0110] After multiple data analyses, it was found that the high-order polynomial fitting method worked best, while the quartic polynomial was underfitting and the sixth-order polynomial was overfitting, so the fifth-order polynomial was selected as the data fitting algorithm. The specific fitting formula is as follows:

[0111] H′(n)=I t +B1·T(n)+B2T(n) 2 +B3T(n) 3 +B4T(n) 4 +B5T(n) 5 ; (2)

[0112] Among them, T(n) is the temperature difference between adjacent time points, T(n)=t(n+1)-t(n), n≤N-1, the MCU module will automatically calculate the temperature intercept I in the formula through a high-order polynomial fitting algorithm t And the constant values ​​of B1, B2, B3, B4, and B5.

[0113] The H of the monitoring point calculated using S3 ′ Substitute (n) and T(n) into the above formula and get I t , B1, B2, B3, B4, B5, then return to the above formula and replace H with D ′(n), T replaces T(n), and the relationship model between liquid level difference and temperature difference is obtained:

[0114] D=I t +B1·T+B2T 2 +B3T 3 +B4T 4 +B5T 5 ; (3)

[0115] Among them, D represents the liquid level error caused by temperature change, and T represents the temperature difference. At this time, T represents the difference between the temperature at the current moment and the temperature at the previous moment. The density of the moment depends on the time interval of temperature collection.

[0116] Fig.10 This is a scatter plot comparing the relationship between the temperature difference and the liquid level difference at adjacent time points after the data of the pressure differential static level is fitted. It can be seen that the relationship diagram after fitting is compared Fig. 9 Before fitting, it is smoother and shows a strong negative correlation.

[0117] S4, perform liquid level difference correction:

[0118] In subsequent measurements, the temperature value and liquid level value are collected through the temperature sensor module and the pressure sensor. The temperature difference caused by the temperature change is substituted into the formula (3) of S3 to obtain the liquid level error caused by the temperature change at the current time point. The corrected liquid level value at the current time point can be obtained by subtracting the liquid level error caused by the temperature from the liquid level value at the current time point.

[0119] The corrected liquid level value obtained at this time is the liquid level value that eliminates the influence of temperature, which is more accurate than the settlement value directly output by the traditional measurement method.

[0120] In one embodiment of the present invention, for example Fig.11 The set of measurement data shown in the figure is processed to obtain Fig.12 and Fig.13 ; Fig.12 is the temperature difference calculated directly without using temperature correction, and Fig.13 It is the temperature difference value after the level error caused by temperature is corrected. However, due to the characteristics of diffused silicon sensors, the error value caused by external factors cannot be completely eliminated. Fig.12 The maximum absolute value of the level difference fluctuation that has not been fitted by the algorithm is 0.56mm, and the average absolute value is 0.10mm. Fig.13 The maximum absolute value of the level difference fluctuation after algorithm fitting is 0.32mm, and the absolute and average values ​​are 0.07mm. By comparison, it can be found that the corrected partial level difference eliminates the influence of temperature difference changes, making the measurement data more accurate.

[0121] S5, use sliding window to improve the model:

[0122] The model generated by the above steps is determined by the weather of the week when the data is collected. Due to weather changes, the temperature difference of the next week may exceed the model range, resulting in the inability to correct the data using the previous fitting algorithm. At this time, it is necessary to manually extract the data of the new week to continue fitting the model, recalculate the constants of the fitting algorithm, and continuously improve the model of the liquid level correction algorithm over time.

Claims

1. A pressure differential static level based on POWERBUS, comprising a liquid storage chamber and a circuit chamber fixedly connected, a through hole formed between the liquid storage chamber and the circuit chamber, a circuit unit arranged in the through hole, and the liquid storage chambers and circuit chambers of a plurality of the pressure differential static levels are connected respectively, characterized in that: The circuit unit includes an MCU module and a temperature sensor module electrically connected thereto, a reference power module, a data storage chip, a POWERBUS communication module and a pressure sensor; POWERBUS communication interfaces are also provided on both sides of the circuit cavity; The MCU module is used to receive data from the temperature sensor module and the pressure sensor and store the data in the data storage chip after processing; The reference power supply module is used to supply power to other components in the circuit unit; The POWERBUS communication module is used to transmit data between the pressure differential static level gauges through the POWERBUS communication interface; The circuit cavity is fixedly connected to the plane to be measured via a bottom plate fixedly connected to the circuit cavity.

2. The differential pressure static level according to claim 1, characterized in that: The top of the liquid storage chamber is also provided with a transparent liquid observation window and a horizontal bubble groove; The liquid observation window is used to observe whether there are bubbles remaining inside the liquid storage cavity; The level bubble groove is used to judge whether the pressure differential type static level is installed horizontally through the level bubble movably connected thereon.

3. A liquid level correction algorithm based on the differential pressure static level according to claim 1 or 2, characterized in that: The following steps are involved: S1, data collection: Use the temperature sensor module and the pressure sensor to collect a total of N liquid level height values ​​h(n) and temperature values ​​t(n), n∈[1,N], and n is a time point; S2, the fluctuation value of the filtered liquid level difference: Calculate the liquid level difference H(n) at adjacent time points, H(n) = h(n+1)-h(n), n≤N-1; A fifth-order polynomial is used to fit the liquid level difference H(n) between the time point n and the adjacent time points, as shown in formula (1): H(n)=I h +A1·n+A2n 2 +A3n 3 +A4n 4 +A5n 5 ; (1) Among them, I h , A1, A2, A3, A4 and A5 are all constant terms; Get the I h , A1, A2, A3, A4 and A5 are then brought back to formula (1), and then the time point n is brought in to calculate the corrected level difference H at adjacent time points ′ (n), (n≤N-1) relational model; S3, construct the relationship model between liquid level error and temperature difference: Calculate the temperature difference T(n) between adjacent time points, T(n) = t(n+1)-t(n), n≤N-1; Use a fifth-order polynomial to fit the corrected liquid level difference H at adjacent time points ′ (n) and the temperature difference T(n) at adjacent time points, as shown in formula (2): H′(n)=I t +B1·T(n)+B2T(n) 2 +B3T(n) 3 +B4T(n) 4 +B5T(n) 5 ; (2) Among them, I t , B1, B2, B3, B4 and B5 are all constant terms; Get I t , B1, B2, B3, B4 and B5, and then bring back formula (2), and use D to replace H′(n), T to replace T(n), and get the relationship model between liquid level error and temperature difference, which is formula (3): <h2 style=";text-align:left;direction:ltr">D=I<h2 style=";text-align:left;direction:ltr"> t <h2 style=";text-align:left;direction:ltr"> +B1·T+B2T<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> +B3T<h2 style=";text-align:left;direction:ltr"> 3 <h2 style=";text-align:left;direction:ltr"> +B4T<h2 style=";text-align:left;direction:ltr"> 4 <h2 style=";text-align:left;direction:ltr"> +B5T<h2 style=";text-align:left;direction:ltr"> 5 <h2 style=";text-align:left;direction:ltr"> (3) Where D represents the liquid level error caused by temperature change, and T represents the temperature difference at any time; S4, perform liquid level difference correction: After using the temperature sensor module and the pressure sensor to obtain the liquid level height value and the new temperature value at the collection time, the temperature difference between the collection time and the moment before the collection time is calculated and substituted into formula (3) to obtain the liquid level error at the collection time; The corrected liquid level height value at the collection time is obtained by subtracting the liquid level error at the collection time from the liquid level height value at the collection time.

4. The liquid level correction algorithm according to claim 3, characterized in that: The N times of data collection described in S1 are completed within one week.

5. The liquid level correction algorithm according to claim 4 is characterized in that: When collecting liquid level height and temperature values, collect them once every hour.

6. The liquid level correction algorithm according to claim 3, characterized in that: It also includes S5, which uses a sliding window approach to improve the model: The model is continuously fitted using the continuously acquired new liquid level height values ​​and temperature values, and the relationship model of the corrected liquid level difference at adjacent time points in S2 and the relationship model of the liquid level error and the temperature difference in S3 are continuously improved.

7. The liquid level correction algorithm according to claim 3, characterized in that: Any time in S3 is after the time of acquiring data N times in S1.

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