Method for self-calibration of surface acoustic wave pressure in bidirectional flow valve

Abstract

The present application relates to the technical field of fluid control, in particular to a surface acoustic wave pressure self-calibration method of a bidirectional flow valve, which integrates a surface acoustic wave sensor array on the inner wall of the valve, adopts a hexagonal three-layer arrangement structure, and includes a pressure monitoring layer, a backup layer and a calibration layer; the piezoelectric single crystal resonators on the upper and lower sides of the sensor array adopt different crystal orientations X-cut or Y-cut respectively, and adopt a combination of wide-band multi-mode excitation and low-frequency narrow-band single-mode excitation; a calibration curve of sound velocity and pressure is established by pouring liquid into the valve to different depths; a 2.4 GHz radio frequency signal is acquired, based on the principle that the sound velocity of sound waves in the medium changes with pressure, the real-time pressure value of the flow channel is converted; combined with the data of the valve core displacement sensor, the Kalman filtering method is used to fit the optimal switching curve to predict the water hammer pressure peak value; when the peak value exceeds 80% of the pipe pressure limit, the bypass pressure relief valve is opened, and the inhibition efficiency reaches 90%.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fluid control, in particular to a surface acoustic wave pressure self-calibration method for bidirectional flow valves. BACKGROUND

[0002] In a fluid system, valves are key components for controlling fluid direction and flow rate, and their performance directly affects the stability and reliability of the entire system. Traditional valves often face the phenomenon of water hammer during use, which is a pressure transient phenomenon caused by the sudden stop or change of direction of fluid. This phenomenon can cause serious consequences such as pipe rupture and valve damage. In the prior art, mechanical pressure sensors are often used for pressure monitoring, but they have the disadvantages of slow response speed, low precision, and susceptibility to medium corrosion, making it difficult to accurately monitor and predict water hammer pressure in real time.

[0003] In addition, the traditional valve control system lacks an effective self-calibration mechanism, resulting in a decrease in measurement accuracy and a decrease in system reliability over a long period of time. At the same time, when fluid flows in both directions, the existing technology is difficult to adapt to the pressure variation characteristics under different flow directions, affecting the normal operation of the system.

[0004] To solve the above problems, there is an urgent need for a valve control method that can accurately measure fluid pressure, predict water hammer phenomenon in real time, and automatically calibrate. SUMMARY

[0005] The purpose of the present application is to provide a surface acoustic wave pressure self-calibration method for bidirectional flow valves, aiming to solve the technical problems of low pressure measurement accuracy, poor water hammer prediction ability, and lack of effective self-calibration mechanism in existing valve systems.

[0006] The present application provides a surface acoustic wave pressure self-calibration method for bidirectional flow valves, comprising:

[0007] A surface acoustic wave sensor array is integrated into the inner wall of the valve, which includes inner, middle and outer piezoelectric single crystal resonators arranged in a hexagonal structure, wherein the inner layer serves as a pressure monitoring layer, the middle layer serves as a pressure backup layer, and the outer layer serves as a pressure calibration layer;

[0008] Different depths of liquid are poured into the valve to cover the surface acoustic wave sensor array, the change of sound velocity caused by different depths of liquid level is tested, and a calibration curve of real-time pressure and liquid level height inside the valve is established;

[0009] The 2.4GHz radio frequency signal collected by the surface acoustic wave sensor array is obtained, and based on the principle that the sound velocity of sound wave in medium changes with pressure, the radio frequency signal is converted into a real-time pressure value of the flow passage;

[0010] The displacement signal of the valve core displacement sensor is obtained, and the real-time pressure value of the flow passage is combined to fit the optimal switching curve of the valve.

[0011] Predicting water hammer pressure peak, when the water hammer pressure peak is greater than a preset percentage of the pipe pressure limit, opening the bypass pressure relief valve for pressure suppression.

[0012] As preferred, the piezoelectric single crystal resonator bodies on the upper and lower sides of the surface acoustic wave sensor array respectively adopt different crystal orientations X-cut or Y-cut, the transverse XY cross-sectional areas of the piezoelectric single crystal resonator bodies are different, and the transverse XY cross-sectional areas of the surface acoustic wave sensor arrays on the upper and lower sides are complementary to each other.

[0013] As preferred, the upper and lower side excitation electrodes respectively adopt different working frequencies, wide-band multi-mode excitation and low-frequency narrow-band single-mode excitation, wherein the low-frequency narrow-band single-mode excitation electrode is the main excitation electrode, and the wide-band single-mode excitation electrode is the backup excitation electrode.

[0014] As preferred, the surface acoustic wave sensor array in the valve is arranged in 3 layers to form a hexagonal structure of 1 inner layer, 1 middle layer and 1 outer layer, wherein the outer layer is a pressure calibration layer and is provided with a plurality of piezoelectric single crystal resonator bodies; the inner layer is a pressure monitoring layer and is provided with one piezoelectric single crystal resonator body; the middle layer is a pressure backup layer, and the inner layer and the middle layer are each arranged with 6 piezoelectric single crystal resonator bodies.

[0015] As preferred, the liquid of different depths is poured into the valve to cover the surface acoustic wave sensor array, including:

[0016] Pouring 10 cm of liquid, calibrating pressure 15 bar, speed 1 m / s;

[0017] Pouring 15 cm of liquid, calibrating pressure 20 bar, speed 1 m / s;

[0018] Pouring 20 cm of liquid, calibrating pressure 30 bar, speed 1.15 m / s;

[0019] Pouring 25 cm of liquid, calibrating pressure 44 bar, speed 1.2 m / s;

[0020] Pouring 30 cm of liquid, calibrating pressure 50 bar, speed 1.3 m / s;

[0021] Pouring 35 cm of liquid, calibrating pressure 65 bar, speed 1.25 m / s.

[0022] As preferred, the real-time pressure value of the flow channel is combined to fit the optimal switching curve of the valve, including:

[0023] Obtaining initial voltage signal, initial displacement signal and initial current signal;

[0024] Based on the initial voltage signal, the initial displacement signal and the initial current signal, the pre-estimated valve front, valve inside and valve rear pressure is obtained;

[0025] Based on the flow channel real-time pressure value, the valve front, valve inside and valve rear pressure is measured;

[0026] The pre-estimated valve front, valve inside and valve rear pressure is fused with the measured valve front, valve inside and valve rear pressure to obtain a fused pressure signal;

[0027] Based on the fused pressure signal, the switching time of the electromagnet is adjusted to change the axial position of the valve core in the flow channel.

[0028] Preferably, the pre-estimated valve front, valve inside and valve rear pressure adopts Kalman filtering method, and the pre-estimated valve front, valve inside and valve rear pressure is fused with the measured valve front, valve inside and valve rear pressure to realize the double measurement mode of estimation + measurement, so that the most ideal flow channel switching function is realized.

[0029] Preferably, when the water hammer pressure peak value is greater than 80% of the pipe pressure limit, the bypass pressure relief valve is opened, and the pressure fluctuation suppression efficiency is improved by 90%.

[0030] Preferably, if the liquid is poured from the bottom, the bottom layer of the valve body corresponds to the liquid level height of the liquid, the upper surface, the lower surface and the side surface of the surface acoustic wave sensor array are directly contacted with the liquid, and when the liquid enters the valve, the valve inside pressure is calculated through different responses of different crystal orientation and different size piezoelectric single crystal resonator to pressure; if the liquid is poured from the top of the valve body, the valve inside pressure is calculated through the response of different surface acoustic wave resonators to pressure.

[0031] Preferably, the thickness-diameter ratio of the piezoelectric single crystal resonator is between 0.05-0.3, the bypass pressure relief valve is a normally open type pipeline, located on the bypass pipeline of the switching valve, the switching valve is a 2-control 2-reversing switching valve, and the liquid flow pipeline and the gas flow pipeline are communicated in the switching valve.

[0032] The present application has the following beneficial effects:

[0033] 1. High measurement accuracy: the surface acoustic wave technology is used to measure the pressure, and the accuracy can reach ±0.5%, which is much better than the traditional mechanical sensor of ±2%;

[0034] 2. Fast response speed: the system response time is less than 1ms, which can capture transient pressure changes and provide reliable data basis for water hammer prediction;

[0035] 3. Water hammer prediction and suppression effect is remarkable: when the predicted water hammer pressure peak value is greater than 80% of the pipeline pressure limit, the bypass pressure relief mechanism is started, and the pressure fluctuation suppression efficiency can be improved by 90%;

[0036] 4. Strong self-calibration capability: through multi-point calibration and dynamic calibration technology, the system can maintain high-precision measurement capability for a long time, and adapt to different fluid media and working conditions;

[0037] 5. Good bidirectional adaptability: the system can automatically adjust the measurement strategy according to the fluid flow direction, and is suitable for various installation environments and working conditions with changing flow direction. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 The system structure schematic diagram of the surface acoustic wave pressure self-calibration method of the bidirectional flow valve of the application;

[0039] Figure 2 The arrangement structure schematic diagram of the surface acoustic wave sensor array in the application;

[0040] Figure 3 The internal structure schematic diagram of the surface acoustic wave sensor in the application;

[0041] Figure 4 The pressure calibration curve establishment process schematic diagram in the application;

[0042] Figure 5 The control flow chart of the valve switching process in the application;

[0043] Figure 6 The water hammer pressure prediction and suppression effect comparison chart in the application. DETAILED DESCRIPTION

[0044] Please refer to the accompanying Figures 1-6 , the application will be further described in detail below in combination with the drawings and specific embodiments.

[0045] Embodiment 1

[0046] As shown in Figure 1 , the application provides a surface acoustic wave pressure self-calibration method of a bidirectional flow valve. The method first integrates a surface acoustic wave (SAW) sensor array on the inner wall of the valve. As shown in Figure 2 , the surface acoustic wave sensor array is arranged in a hexagonal structure, including inner layer, middle layer and outer layer piezoelectric single crystal resonator, wherein the inner layer is used as a pressure monitoring layer, the middle layer is used as a pressure backup layer, and the outer layer is used as a pressure calibration layer.

[0047] In a preferred embodiment of the application, as Figure 3As shown, in the surface acoustic wave (SAW) sensor array, the piezoelectric single-crystal resonators on the upper and lower sides are cut with different crystal orientations (X-cut or Y-cut), and the transverse (XY) cross-sectional areas of each piezoelectric single-crystal resonator are unequal. Furthermore, the transverse (XY) cross-sectional areas of the upper and lower sides of the SAW sensor array are complementary. This differentiated design allows the sensor array to capture pressure signals from different angles, improving the comprehensiveness and accuracy of the measurement. For example, when the fluid pressure inside the valve changes, the X-cut crystal is more sensitive to pressure changes in the vertical direction, while the Y-cut crystal is more sensitive to pressure changes in the parallel direction. By using them in combination, more comprehensive pressure distribution information can be obtained.

[0048] Furthermore, the upper and lower excitation electrodes employ different operating frequencies and wideband multimode excitation and low-frequency narrowband single-mode excitation, respectively. The low-frequency narrowband single-mode excitation electrode serves as the primary excitation electrode, while the wideband single-mode excitation electrode serves as a backup. Preferably, the low-frequency narrowband single-mode excitation operates at 2.4 GHz with a bandwidth of ±10 MHz, while the wideband multimode excitation covers the 2.2-2.6 GHz range. This dual-mode excitation mechanism enhances system reliability; even in the event of a failure of the primary excitation electrode, the backup excitation electrode ensures normal system operation.

[0049] In another embodiment of the present invention, the surface acoustic wave sensor array within the valve is arranged in three layers, forming a hexagonal structure with an inner layer, a middle layer, and an outer layer. The outer layer serves as a pressure calibration layer and contains multiple piezoelectric single-crystal resonators; the inner layer serves as a pressure monitoring layer and contains one piezoelectric single-crystal resonator; the middle layer serves as a pressure backup layer, with six piezoelectric single-crystal resonators arranged in both the inner and middle layers. This multi-layered arrangement provides data redundancy and backup functionality, significantly improving system reliability. In practical applications, when a sensor in one layer fails, the system can automatically switch to sensors in other layers to continue operation, ensuring measurement continuity.

[0050] In practical applications, the surface acoustic wave sensor array first needs to be calibrated. For example... Figure 4 As shown, the calibration process includes filling the valve with liquid to different depths to cover the surface acoustic wave sensor array, testing the sound velocity changes caused by different liquid levels, and establishing calibration curves for real-time pressure and liquid level inside the valve. Specific calibration steps include:

[0051] Fill with 10 cm of liquid, set the pressure to 15 bar, and the speed to 1 m / s;

[0052] Pour in 15 cm of liquid, set the pressure to 20 bar, and the speed to 1 m / s;

[0053] Pour in 20 cm of liquid, set the pressure to 30 bar, and the speed to 1.15 m / s;

[0054] Filling 25 cm liquid, rated pressure 44 bar, speed 1.2 m / s;

[0055] Filling 30 cm liquid, rated pressure 50 bar, speed 1.3 m / s;

[0056] Filling 35 cm liquid, rated pressure 65 bar, speed 1.25 m / s.

[0057] Through this multi-point calibration method, the system can establish an accurate sound speed-pressure correspondence, providing a basis for subsequent pressure measurement. During calibration, to prevent gas from entering the valve, the switching valve must be closed after filling the gas, pressure self-calibration and algorithm optimization are performed, and then the gas is discharged. This can avoid the interference of bubbles on the propagation of sound waves and ensure the accuracy of calibration.

[0058] After calibration, the system obtains the 2.4 GHz radio frequency signal collected by the surface acoustic wave sensor array during operation. Based on the principle that the sound speed of sound waves in the medium changes with pressure, the radio frequency signal is converted into the real-time pressure value of the flow passage. This conversion process can be achieved through the following formula:

[0059] ,

[0060] wherein, is the flow passage pressure (Pa), is the calibration coefficient (dimensionless), is the frequency change (Hz), is the reference frequency (Hz), is the sound wave propagation speed in the medium (m / s), is the medium density (kg / m 3 ).

[0061] In an actual bidirectional flow valve system, the value is usually determined according to the calibration experiment, and for common liquids such as water, the value is about 0.15-0.25. is 2.4 GHz, usually in the range of several thousand Hz, depending on the size of the pressure change. For example, when the fluid pressure changes from 1 MPa to 1.5 MPa, about 5000 Hz. For water, about 1000 kg / m 3 , about 1500 m / s. In valve applications, the sound wave speed The sound speed will change with temperature, so the system also needs to be temperature compensated to ensure measurement accuracy. The sound speed increases by about 3 m / s for every 1 °C increase in temperature. By installing a temperature sensor near the sensor, this effect can be compensated in real time.

[0062] At the same time, the system acquires the displacement signal of the spool displacement sensor. In the present application, a Hall effect displacement sensor is preferably used, with a measurement range of 0-10 mm, an accuracy of ±0.01 mm, and a sampling frequency of 1 kHz. The system combines the real-time pressure value of the flow channel and the spool displacement signal to fit the optimal switching curve of the valve, which describes the relationship between the spool position and the fluid pressure distribution, and is the key to achieving smooth switching.

[0063] As shown in Figure 5 , the fitting process specifically includes:

[0064] 1. Obtain the initial voltage signal, initial displacement signal, and initial current signal;

[0065] 2. Estimate the pressure before, in, and after the valve based on the initial voltage signal, initial displacement signal, and initial current signal;

[0066] 3. Measure the pressure before, in, and after the valve based on the real-time pressure value of the flow channel;

[0067] 4. Fuse the estimated pressure before, in, and after the valve with the measured pressure before, in, and after the valve to obtain a fused pressure signal;

[0068] 5. Adjust the switching time of the electromagnet based on the fused pressure signal to change the axial position of the spool in the flow channel.

[0069] In the preferred embodiment of the present application, the estimated pressure before, in, and after the valve uses the Kalman filter method. The Kalman filter algorithm is a recursive least squares estimation method, which is particularly suitable for dynamic system state estimation. In a bidirectional flow valve, the fluid state changes rapidly over time, and the Kalman filter can effectively handle measurement noise and system uncertainty to provide more accurate state estimation. Its basic formula is as follows:

[0070] 1. Prediction step:

[0071] ,

[0072] ,

[0073] 2. Update step:

[0074] ,

[0075] ,

[0076] ,

[0077] where, is the prior state estimate at time k (containing pre-valve, in-valve and post-valve pressure values in Pa), is the posterior state estimate at time k (Pa), is the state transition matrix (dimensionless), is the control input matrix (dimensionless), is the control vector (containing spool position and driving current in mm and A, respectively), is the prior estimation error covariance matrix (Pa 2 ), is the posterior estimation error covariance matrix (Pa 2 ), is the Kalman gain (dimensionless), is the observation matrix (dimensionless), is the observation vector (i.e. pressure values measured by SAW sensors in Pa), is the process noise covariance matrix (Pa 2 ), is the observation noise covariance matrix (Pa 2 ), is the identity matrix (dimensionless), and superscript T denotes matrix transpose.

[0078] In bidirectional flow valve applications, the state vector is a 3x1 column vector containing pre-valve, in-valve and post-valve pressure values, the state transition matrix is a 3x3 matrix describing how the pressure state evolves from one time instant to the next, usually determined from fluid dynamics models. The observation vector is a 3x1 column vector containing pressure measurements from different location SAW sensors. The observation matrix is a 3x3 matrix mapping the state space to the observation space.

[0079] The process noise covariance matrix and the observation noise covariance matrix are usually determined experimentally. In typical bidirectional flow valve applications, the diagonal elements of matrix 2 may be set to 0.01-0.1 MPa , reflecting the uncertainty in the prediction of system states; the diagonal elements of matrix 2 may be set to 0.1-1.0 MPa , reflecting the noise level in the measurement process. The specific values of these parameters need to be adjusted according to the valve operating conditions and the accuracy of the measurement equipment.

[0080] By fusing the estimated pressure with the measured pressure, a dual measurement mode of estimation + measurement is adopted to achieve the most ideal flow channel switching function. The fusion process is essentially completed through the update step of the Kalman filter, where the Kalman gain... This determines the weighting of the estimated and measured values. In practical valve control, if the sensor measurements are highly reliable, then... If the value is large, the measured value is preferred; if the measurement noise is high, then... For smaller values, it is more likely to use estimated values.

[0081] Based on the fused pressure signal, the system predicts the peak water hammer pressure. The formula for predicting the peak water hammer pressure is as follows:

[0082] ,

[0083] in, The predicted peak water hammer pressure (Pa). Current pressure (Pa), Fluid density (kg / m³) 3 ), The velocity of sound (m / s). The change in flow velocity (m / s) The safety factor (dimensionless) is usually taken as 0.1-0.3.

[0084] In practical applications of bidirectional flow valves, such as when the valve is rapidly closed from a fully open state, the change in flow rate is... It could reach 23 m / s, for a density of 1000 kg / m³. 3 Under conditions of water and a sound velocity of approximately 1500 m / s, the water hammer pressure increase can reach 3-4.5 MPa, sufficient to damage ordinary pipeline systems. By predicting this pressure peak, the system can take preventative measures to avoid pipeline damage.

[0085] When the predicted peak water hammer pressure exceeds a preset percentage of the pipeline's pressure-bearing limit, the system will open a bypass pressure relief valve to suppress the pressure. In one specific embodiment of the invention, when the peak water hammer pressure exceeds 80% of the pipeline's pressure-bearing limit, opening the bypass pressure relief valve can improve the pressure fluctuation suppression efficiency by 90%. For example, for a pipeline system with a pressure-bearing limit of 6 MPa, when the predicted peak water hammer pressure exceeds 4.8 MPa, the system will automatically open the bypass pressure relief valve to control the pressure peak within a safe range. Figure 6 As shown, compared with traditional methods, the water hammer suppression effect of the present invention is significant.

[0086] The present application also considers the flow direction of the fluid. If the liquid is filled from the bottom, the bottom layer of the valve body corresponds to the liquid level of the liquid, the upper surface, the lower surface and the side surface of the surface acoustic wave sensor array are directly in contact with the liquid, and the pressure in the valve is calculated by the different responses of the piezoelectric single crystal resonator bodies with different crystal orientations and different sizes to the pressure when the liquid enters the valve. If the liquid is filled from the top of the valve body, the pressure in the valve is calculated by calculating the response of different surface acoustic wave resonator bodies to the pressure. This design enables the system to adapt to different installation directions and flow conditions, and the system can work normally regardless of how the valve is installed.

[0087] In another embodiment of the present application, the thickness-to-diameter ratio of the piezoelectric single crystal resonator body is between 0.05 and 0.3. The thickness-to-diameter ratio refers to the ratio of the thickness to the diameter of the piezoelectric single crystal resonator body, which directly affects the resonant frequency and sensitivity. A smaller thickness-to-diameter ratio (such as 0.05-0.1) is beneficial to obtain higher sensitivity, while a larger thickness-to-diameter ratio (such as 0.2-0.3) helps to improve mechanical strength and stability. In practical applications, a suitable thickness-to-diameter ratio can be selected according to specific requirements. For example, for high pressure environments (>1MPa), a thickness-to-diameter ratio of 0.15-0.25 is recommended to balance sensitivity and mechanical strength; for low pressure environments (<0.5MPa), a thickness-to-diameter ratio of 0.05-0.15 can be selected to obtain higher sensitivity.

[0088] In addition, the bypass pressure relief valve is a normally open type pipe located on the bypass pipe on one side of the switching valve, and the switching valve is a 2-control 2-way switching valve with liquid flow pipes and gas flow pipes connected inside. This design ensures that the bypass pressure relief valve can quickly open when the system is abnormal to prevent water hammer pressure from causing system damage. In normal operation, the 2-control 2-way switching valve can switch the liquid flow and gas flow channels as needed to achieve bidirectional fluid control.

[0089] In summary, the surface acoustic wave pressure self-calibration method of the bidirectional flow valve provided by the present application realizes high-precision measurement of flow channel pressure, accurate prediction of water hammer pressure, and effective pressure fluctuation suppression by integrating a specially designed surface acoustic wave sensor array on the inner wall of the valve and combining advanced signal processing and control algorithms. This method has the advantages of high measurement accuracy, fast response speed, strong self-calibration capability, and good bidirectional adaptability, and can effectively solve the technical problems faced by traditional valve systems and improve the safety and reliability of fluid systems.

[0090] The above-described embodiments only express the specific implementation of the present application, which is described in detail and specifically, but should not be construed as limiting the scope of the present application. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of protection of the present application.

Claims

1. A method of self-calibration of a surface acoustic wave pressure in a bidirectional flow valve, characterized in that, The utility model relates to a valve pressure monitoring and control system based on acoustic surface wave sensor array, comprising: Integrating acoustic surface wave sensor array in valve inner wall, the acoustic surface wave sensor array includes the inner layer, the middle layer and the outer layer piezoelectric single crystal resonator body arranged in hexagonal structure, wherein the inner layer is as pressure monitoring layer, the middle layer is as pressure backup layer, and the outer layer is as pressure calibration layer; Filling liquid of different depth in valve to cover the acoustic surface wave sensor array, testing acoustic velocity change caused by different depth liquid level, and establishing calibration curve of real-time pressure and liquid level height inside valve; Acquiring 2.4GHz radio frequency signal collected by the acoustic surface wave sensor array, and converting the radio frequency signal into flow passage real-time pressure value based on the principle that acoustic velocity changes with pressure in medium; Acquiring displacement signal of valve core displacement sensor, combining the flow passage real-time pressure value, and fitting optimal switching curve of valve; Predicting water hammer pressure peak value, and opening bypass pressure relief valve to carry out pressure suppression when the water hammer pressure peak value is greater than preset percentage of pipeline pressure limit; The acoustic surface wave sensor array in the valve is arranged in 3 layers, forming a hexagonal structure of 1 inner layer, 1 middle layer and 1 outer layer, wherein the outer layer is as pressure calibration layer and is provided with a plurality of piezoelectric single crystal resonator bodies; the inner layer is as pressure monitoring layer and is provided with one piezoelectric single crystal resonator body; the middle layer is as pressure backup layer, and the outer layer and the middle layer are each arranged with six piezoelectric single crystal resonator bodies; The filling liquid of different depth in valve to cover the acoustic surface wave sensor array comprises: Filling 10cm liquid, calibrating pressure 15bar, and velocity 1m / s; Filling 15cm liquid, calibrating pressure 20bar, and velocity 1m / s; Filling 20cm liquid, calibrating pressure 30bar, and velocity 1.15m / s; Filling 25cm liquid, calibrating pressure 44bar, and velocity 1.2m / s; Filling 30cm liquid, calibrating pressure 50bar, and velocity 1.3m / s; Filling 35cm liquid, calibrating pressure 65bar, and velocity 1.25m / s.

2. The method of claim 1, wherein the SAW pressure self-calibration method is applied to a bi-directional flow valve. In the acoustic surface wave sensor array, the piezoelectric single crystal resonator bodies on the upper and lower sides adopt different crystal orientations X-cut or Y-cut respectively, the transverse XY cross-sectional areas of the piezoelectric single crystal resonator bodies are different, and the transverse XY cross-sectional areas of the acoustic surface wave sensor arrays on the upper and lower sides are complementary to each other.

3. The method of claim 2, wherein the SAW pressure self-calibration method is applied to a bi-directional flow valve. The upper and lower side excitation electrodes adopt wideband multi-mode excitation and low-frequency narrowband single-mode excitation with different working frequencies respectively, wherein the low-frequency narrowband single-mode excitation electrode is as a main excitation electrode, and the wideband multi-mode excitation electrode is as a backup excitation electrode.

4. The method of claim 1, wherein the SAW pressure self-calibration method is applied to a bi-directional flow valve. The fitting optimal switching curve of valve by combining the flow passage real-time pressure value comprises: Acquiring initial voltage signal, initial displacement signal and initial current signal; Estimating pressure before, in and after valve based on the initial voltage signal, the initial displacement signal and the initial current signal; Measuring pressure before, in and after valve based on the flow passage real-time pressure value; Fusing the estimated pressure before, in and after valve with the measured pressure before, in and after valve to obtain fused pressure signal. Based on the fusion pressure signal, the switching time of the electromagnet is adjusted to change the axial position of the valve core in the flow channel.

5. The method of claim 4, wherein the SAW pressure self-calibration method is for a bidirectional flow valve. The estimated pre-valve, in-valve and post-valve pressures are fused with the measured pre-valve, in-valve and post-valve pressures by using a Kalman filter method, and a double measurement mode of estimation and measurement is used to realize the most ideal flow channel switching function.

6. The method of claim 1, wherein the SAW pressure self-calibration method is for a bidirectional flow valve. When the water hammer pressure peak is greater than 80% of the pipe pressure limit, the bypass pressure relief valve is opened, and the pressure fluctuation suppression efficiency is improved by 90%.

7. The method of claim 1, wherein the SAW pressure self-calibration method is for a bidirectional flow valve. When liquid is filled from the bottom, the bottom layer of the valve body corresponds to the liquid level height of the liquid, and the upper surface, lower surface and side surface of the surface acoustic wave sensor array are directly in contact with the liquid.

8. The method of claim 1, wherein the SAW pressure self-calibration method is for a bidirectional flow valve. The thickness-diameter ratio of the piezoelectric single crystal resonator is between 0.05 and 0.3, the bypass pressure relief valve is a normally open pipeline, and is located on the bypass pipeline of one side of the switching valve. The switching valve is a 2-control 2-reversing switching valve, and the liquid flow pipeline and the gas flow pipeline are connected in the switching valve.

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