Aircraft hydraulic pipeline ultrasonic pressure measurement system and dynamic compensation measurement method

Abstract

The invention belongs to the technical field of non-intrusive pressure detection, and particularly relates to an aircraft hydraulic pipeline ultrasonic pressure measuring system and a dynamic compensation method. The measuring system comprises a control module, a sending module, a receiving module, a data processing module, a first ultrasonic transducer, a second ultrasonic transducer and a temperature sensor. The control module generates an ultrasonic driving signal complementary PWM wave, the sending module drives and amplifies an ultrasonic signal emitted by the first ultrasonic transducer, the control module synchronously sends the signal to the data processing module TDC for timing, an ultrasonic signal collected by the second ultrasonic transducer is converted into an electric signal through the receiving module, and the electric signal is sent to the control module. The control module is also used for performing algorithm fusion processing on the signal processed by the DSP and the time of the data processing module, and displaying through the man-machine interaction module; the data processing module is used for forming a three-dimensional array according to the transition time values delta t at different temperatures and different pressures; through a bilinear interpolation method, the static pressure P static is solved at any temperature and transition time; the temperature sensor collects temperature signals in real time, converts the temperature signals into electric signals and transmits the electric signals to the control module. According to the invention, the system is high in measurement efficiency, more accurate in measurement and capable of responding to rapid sudden pressure change.

Description

Technical Field

[0001] The invention belongs to the technical field of non-intrusive pressure detection, and in particular relates to an aircraft hydraulic pipeline ultrasonic pressure measurement system and a dynamic compensation method. Background Art

[0002] The propagation speed of ultrasound in the medium is related to the density and elastic modulus of the medium. The change in pressure causes the volume elastic modulus K, pressure p and density ρ to change, which ultimately causes the change in the propagation speed of ultrasound in the liquid. Temperature changes will inevitably cause changes in the speed of sound, which will further affect the results of ultrasonic flow measurement. Therefore, temperature compensation must be performed on ultrasonic flow measurement.

[0003] Under current technology, the non-invasive ultrasonic compensation method for pipeline liquid pressure is to use a temperature sensor to measure the surface temperature of the pipe wall, and then compensate for the measured ultrasonic transit time, and finally establish the corresponding relationship between ultrasonic sound velocity and pressure, and calculate the liquid pressure value in the pipeline by the measured sound velocity. The existing ultrasonic measurement compensation method is based on the linear relationship between sound velocity and temperature and sound velocity and pressure for relevant conversion and compensation, such as the patent with the publication number of "CN112915452A" and the patent name of "Non-invasive fire hydrant water pressure detection method based on multi-ultrasonic signal delay accumulation". This method mentions compensating the ultrasonic sound velocity by the pipe wall temperature and the ambient temperature, but all the temperature static compensation is mentioned. For example, patent CN116718307A discloses a non-invasive ultrasonic measurement of pipeline liquid pressure compensation method and system. This patent is generally more suitable for large-diameter pipelines. Its compensation process has no dynamic real-time correction, and the measurement waiting time is long, which is not suitable for aircraft hydraulic pipeline pressure measurement.

[0004] In the field of aviation hydraulic pipelines, there are scenarios where pressure changes suddenly. When the pressure increases, the temperature of the liquid in the pipeline increases, and when the pressure decreases, the temperature of the liquid in the pipeline decreases. This involves the conversion between temperature thermal energy and pressure potential energy, and the temperature cannot change suddenly with the pressure, so this will cause the existing temperature compensation method to produce a large deviation in pressure measurement within a few minutes of the pressure change. Summary of the invention

[0005] Purpose of the invention: In view of the problems existing in the current pipeline pressure measurement technology, the present invention designs an aircraft hydraulic pipeline ultrasonic pressure measurement system and a dynamic compensation method, which can make the system measure efficiently, more accurately, and respond to rapid sudden changes in pressure.

[0006] Technical solution: The present invention specifically proposes an ultrasonic pressure measurement system for an aircraft hydraulic pipeline, the measurement system comprising: a control module, a sending module, a receiving module, a data processing module, a first ultrasonic transducer, a second ultrasonic transducer, and a temperature sensor;

[0007] The control module generates a complementary PWM wave of an ultrasonic driving signal, and drives and amplifies the first ultrasonic transducer to transmit an ultrasonic signal through the sending module. The control module synchronously sends a signal to the data processing module TDC for timing. The ultrasonic signal collected by the second ultrasonic transducer is converted into an electrical signal by the receiving module and sent to the control module.

[0008] The control module also performs algorithm fusion processing on the signal processed by the DSP and the time of the data processing module, and displays it through the human-computer interaction module;

[0009] The data processing module forms a three-dimensional array of transit time values ​​Δt at different temperatures and pressures; and solves the static pressure P at any temperature and transit time by bilinear interpolation. 静 ;

[0010] The temperature sensor collects temperature signals in real time and converts them into electrical signals for transmission to the control module.

[0011] Furthermore, the data processing module performs median filtering on the two sets of measured time values, and also performs median filtering on the measured temperature value; the two time values ​​are fused by the Kalman fusion algorithm to obtain the final ultrasonic propagation time. The pressure value data corresponding to the propagation time and temperature stored in the system calibration data table are read, and the measured temperature and time values ​​are converted into the final pipeline liquid pressure value by using the bilinear interpolation method.

[0012] Further, the data processing module includes an analog front end, a digital TDC, and an arithmetic unit (ALU); the digital TDC is composed of a precision counter and a coarse value counter, and is mainly responsible for the conversion and transmission of signals to the digital TDC. Specifically, the digital TDC is composed of a precision counter and a coarse value counter, and is responsible for converting the front end effective signal into a unit time. The arithmetic unit calibrates the unit time stored in the digital TDC into a standard time related to the reference clock, and stores it in a corresponding result register;

[0013] The precision counter can measure up to 15PS, with a minimum resolution of 3.8ps (1LSB). The precision counter counts in the range of 0 to 2us, while the coarse counter counts in the range of 500ns to 4ms @ 4MHz. The high-speed unit of the TDC does not measure the entire time interval, but only measures the interval from the START or STOP signal to the adjacent reference clock rising edge (precision counter). Between two precision measurements, the TDC records the number of cycles of the reference clock (coarse counter). Therefore, the time measurement result is the sum of the precision measurement value and the coarse measurement value. The digital TDC has the ability to sample 8 times of STOP, but each STOP interval is not less than 2×Tref.

[0014] The function of the arithmetic unit (ALU) is to process the value of the digital TDC count, mainly to calibrate the value of the digital TDC, save the calibrated value to the corresponding result register and status register, and also accumulate the expected STOP signal sum and store the accumulated value in the corresponding result register.

[0015] The analog front end unit is mainly responsible for signal conversion and transmission to the digital TDC. The analog front end is composed of a precision comparator, a programmable bias voltage generator, a first wave processor, and a high-speed switch; the analog front end can use digital signals and analog signals.

[0016] On the other hand, the present invention also proposes a method for measuring the ultrasonic pressure dynamic compensation of an aircraft hydraulic pipeline, using the measurement system designed as above, constructing a measurement model, placing two ultrasonic transducers on both sides of the pipeline, one ultrasonic transducer for signal transmission, and one ultrasonic transducer for signal reception, processing the transmitted to received signals, and solving the ultrasonic propagation time;

[0017] By measuring multiple groups of time values ​​at specified temperatures and specified pressures, a three-dimensional grid array is formed; by using bilinear interpolation, the temperature value and transit time value of the pipeline are measured to calculate the pressure value in the pipeline.

[0018] Furthermore, the method specifically comprises the following steps:

[0019] Step 1: Collect the transit time values ​​Δt at different temperatures and pressures to form a three-dimensional array; use bilinear interpolation to solve the static pressure P at any temperature and transit time. 静 ;

[0020] Specifically, the pipeline is connected to a standard pressure generator with a range of 0 to 25 MPa, and the pipeline is placed in an incubator. The incubator temperature is set at a temperature point every 5°C within the range of 0°C to 60°C. After each temperature setting, it is necessary to wait for 2 hours for the pipeline temperature to stabilize before proceeding to the next step. At each temperature point, the pipeline pressure is pressurized to 0MPa, 1MPa, 5MPa, 10MPa, 15MPa, 20MPa, and 25MPa respectively. At each pressure point, it is necessary to wait until the temperature and pressure are constant, and collect the ultrasonic transit time value Δt.

[0021] Step 2: Calculate the conversion coefficient r between pressure and temperature; fill the pipeline with hydraulic oil, close the pipeline, connect the pipeline to the pressure transmitter, and put them in a temperature box. Set the temperature of the temperature box within the range of 0℃ to 60℃, and set it as a temperature point every 5℃. After each temperature setting, wait for 2 hours for the pipeline temperature to stabilize, and read the pressure value Pn at each temperature point; calculate a set of coefficients rn based on the recorded multiple sets of pressure points and temperature points, and take the average value as the final coefficient r.

[0022] Step 3: Collect pressure decay data and calculate the exponential decay coefficient k; connect the pipeline to the pressure source and place it in the incubator, set any temperature point, and wait for 2 hours for the temperature to stabilize. Pressurize the pipeline to ΔP 加 Near the pressure point, close the stop valve (i.e., do not perform pressure compensation control) and record the pressure change curve over time within 5 minutes.

[0023] Let ΔP 衰 The pressure difference between the start and end of recording is summarized through multiple experiments: ΔP 衰 =α*ΔP 加 , where α is the proportional coefficient, and the pressure transformation ΔP, then α*ΔP pressure potential energy is converted into temperature internal energy, and α is between 0 and 1.

[0024] From the formula: ΔP = ΔT × r, we can get ΔT = ΔP 衰 / r, that is, the pressure decay curve can be expressed by the temperature decay curve, that is: ΔP(t) = ΔP 衰 / re -kt , combined with the pressure conversion curve data, the attenuation coefficient k value can be obtained by fitting the data through the least squares method.

[0025] Step 4: Calculate the liquid pressure value P in the pipeline in real time based on the currently measured transit time Δt and temperature T. The formula is as follows:

[0026]

[0027] The temperature velocity of sound coefficient compensation method is used to subtract the velocity of sound change caused by temperature change from the measured velocity of sound change, thereby obtaining the velocity of sound change caused by pressure change. The temperature velocity of sound coefficient can be obtained through experiments.

[0028] c=αT 2 +βT+γ

[0029] Where c is the actual sound speed under atmospheric pressure, α, β, γ are the temperature sound speed coefficients, and T is the measured temperature.

[0030] Technical effect: The aircraft hydraulic pipeline ultrasonic pressure measurement system and dynamic compensation method proposed in the present invention can be widely used to realize the hydraulic pipeline pressure measurement on board. For the measurement scenario of rapid and sudden changes in pressure of small-diameter hydraulic pipelines on board, the dynamic compensation method can greatly reduce the waiting time for pressure changes, with high measurement accuracy, fast response speed, significantly improved measurement efficiency, and a wide range of on-board applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic diagram of the test structure for installing the present invention;

[0032] Figure 2 It is a schematic diagram of the structure of the measurement system of the present invention;

[0033] Figure 3 This is the overall measurement flow chart of the present invention. DETAILED DESCRIPTION

[0034] In order to more clearly illustrate the technical solution of the embodiment of the present invention, the present invention is described in detail below in conjunction with the drawings or specific implementation cases of the specification. It should be noted that some (but not all) of the disclosed examples are shown in the drawings. In fact, many different examples can be described and these examples should not be understood as being limited to the examples set forth herein. On the contrary, these examples are described so that the positive effects of the present invention are more reflected, and any parts not detailed in the text are regarded as known techniques or conventional technical means in the art.

[0035] See attached Figures 1 to 3 , the liquid pressure in the pipeline causes the liquid elastic modulus to change, which in turn affects the change in the liquid sound velocity. Conversely, based on the measured liquid sound velocity, the change in the liquid elastic modulus can be calculated, and thus the change in the liquid pressure in the pipeline can be inferred, thereby completing the measurement of the liquid pressure in the pipeline. Hydraulic oil belongs to hydrocarbon substances, and its acoustic properties conform to the law of Kneser liquid. Based on Biccard's research results and the experimental data provided by the "Handbook of Acoustics", the following two main conclusions are drawn: 1) At a certain temperature, the sound velocity increases linearly with the increase of pressure; 2) At a certain pressure, the sound velocity decreases linearly with the increase of temperature:

[0036] P=f(v,T)

[0037] Where P is the liquid pressure value, v is the ultrasonic propagation velocity, and T is the pipe temperature value.

[0038] Measurement diagram Figure 1 As shown: Two ultrasonic transducers are placed on both sides of the pipe, one for signal transmission and the other for signal reception. The transmitted and received signals are processed to calculate the ultrasonic propagation time. As the pressure in the pipe changes, the elastic modulus of the liquid changes, the ultrasonic propagation speed changes, and thus the propagation time changes. Since the pipe diameter is known, the sound velocity can be calculated by measuring the propagation time value.

[0039] The speed of sound is related to the temperature, so a temperature sensor is needed on the pipe surface to measure the temperature. However, the present invention requires the liquid temperature, and the thermal conductivity of metal is relatively high, so an insulation layer is added to the temperature sensor, and the temperature measured by the temperature sensor is assumed to be the liquid temperature.

[0040] By measuring multiple sets of time values ​​at specified temperatures and pressures, a three-dimensional grid array is formed. By measuring the temperature value and transit time value of the pipeline through bilinear interpolation, the pressure value in the pipeline can be calculated. The calculation formula is as follows:

[0041] P=f(Δt,T)=f 00 (1-u)(1-v)+f 10 u(1-v)+f 01 (1-u)v+f 11 uv

[0042] f(Δt,T) represents the function value obtained by interpolation at the point (Δt,T), which is the pressure value P at the temperature T and the transit time Δt.

[0043] f 00 ,f 10 ,f 01 ,f 11 The function values ​​of the four known data points also correspond to the values ​​of the four vertices of the rectangular grid, namely: (Δt0, T0), (Δt1, T0), (Δt0, T1) and (Δt1, T1).

[0044] It is a normalization factor that represents the relative position of the point (Δt, T) in the t-axis direction from the point (Δt0, T0) to (Δt1, T0), and its value range is 0 to 1.

[0045] It is a normalization factor that represents the relative position of the point (Δt, T) in the T-axis direction from the point (Δt0, T0) to (Δt1, T0), and its value range is 0 to 1.

[0046] The above measurement method requires waiting for the pressure and temperature to stabilize before obtaining relatively accurate values. Each pressure change requires waiting for tens of seconds to several minutes. The measurement efficiency is low and the application range is narrow, so dynamic compensation is also required.

[0047] In a liquid, molecules move randomly at high speed and collide with each other frequently. When the outside world applies pressure to the system, that is, reduces its volume, the density of molecules increases, resulting in a significant increase in the frequency and intensity of collisions between molecules. Each collision transfers kinetic energy, which increases the kinetic energy of a single molecule, which overall manifests as an increase in the internal energy of the system. According to the kinetic theory of molecules, the increase in molecular kinetic energy is directly related to the increase in temperature. Pressure can change suddenly, but temperature cannot, relatively speaking. According to the first law of thermodynamics (the law of conservation of energy), energy can neither be created nor destroyed, but can only be converted from one form to another, or transferred from one system to another. In a closed container, after the liquid is pressurized, a small portion of the pressure potential energy is converted into the internal energy of the liquid, causing the temperature to slowly rise, and the pressure to decrease accordingly.

[0048] According to the ideal gas state equation, PV = nRT, (under the condition that the mass n remains unchanged and the volume V is fixed, if the pressure P increases, the temperature T must increase accordingly to maintain the balance on both sides of the equation. Here, R is the ideal gas constant, which reflects the quantitative relationship between pressure, volume, temperature and the amount of substance). It can be inferred that in a liquid environment, the conversion between pressure P and temperature T is a linear relationship. That is:

[0049] ΔP=ΔT×r

[0050] Where ΔP is the pressure change, ΔT is the temperature change, and r is the proportionality coefficient.

[0051] When pressurized, the temperature of the pipe changes, and a thermal equilibrium process is required with the ambient temperature. For the scenario of heat exchange from the pipe to the environment, the non-steady-state (or transient) heat conduction equation can be used to describe the temperature change over time.

[0052]

[0053] ρ is the density of the pipe material, c p is the specific heat capacity. These two parameters together determine the ability of the pipeline material to store thermal energy;

[0054] t is time, which means we are interested in the change of temperature over time;

[0055] x is the coordinate direction along the pipeline, reflecting the temperature distribution in space;

[0056] T is the temperature of the inner or outer surface of the pipe at position x and time t;

[0057] ·The meanings of other symbols are the same as before.

[0058] The left side of the equation describes the rate of change of the internal temperature of the pipeline material over time. The first term on the right side represents heat conduction (heat transfer caused by the temperature gradient inside the pipeline), and the second term is the heat convection term, which reflects the heat exchange between the pipeline and the environment.

[0059] Assuming that the temperature of all parts of the pipeline is the same, this means that we ignore the temperature gradient inside the pipeline and only consider the heat exchange between the pipeline as a whole and the environment. In this case, the problem is simplified to a zero-dimensional heat balance problem, and there is no need to consider the change of the spatial coordinate x. We can use Newton's law of cooling to describe the change of the temperature of the entire pipeline over time, considering the total heat capacity of the pipeline C = ρ·V·c, where V is the volume of the pipeline. The energy balance between the pipeline and the environment can be expressed as:

[0060]

[0061] C is the total heat capacity of the pipe.

[0062] ·T pipe is the average temperature of the pipe surface;

[0063] ·T env is the ambient temperature.

[0064] A is the outer surface area of ​​the pipe,

[0065] h is the convective heat transfer coefficient, which reflects the efficiency of heat transfer between the fluid and the solid surface.

[0066] This equation shows that the rate of change of the pipe temperature with time (left side) is proportional to the heat exchange rate between the pipe and the environment (right side), and the direction is opposite. This is a first-order linear differential equation, and its solution can be obtained by the constant variation method or by directly applying the general solution formula of linear differential equations. The general solution of the equation is:

[0067] T pipe (t) = T env +Ce -kt

[0068] In order to determine the constant C, we need the initial condition, that is, the initial temperature of the pipe at t = 0, Tpipe(0) = T0. Substituting the general solution into the equation, we get: T0 = Tenv + C, which gives C = T0 - Tenv. Finally, the function of the pipe surface temperature changing with time is:

[0069] T pipe (t) = T env +(T0-T env ) -kt

[0070] in Describes the process of the pipe temperature decaying exponentially to the ambient temperature over time.

[0071] In summary, the expression of the final pressure value is:

[0072] P=f(t,T)+ΔPe -kt .

[0073] Figure 2 It is the main structure of the measurement system, including the main control, transmitting module, receiving module, human-computer interaction module, TDC (digital time conversion) module and sensor module (two ultrasonic transducers and one temperature sensor). The main control module is centrally scheduled to control the sending and receiving of ultrasonic signals, control the TDC module, measure the time difference between sending and receiving, drive the temperature sensor to measure the surface temperature of the pipe wall, and realize the display of measurement results and the parameter setting of the equipment through the human-computer interaction module. The transmitting module and the receiving module are used to match the ultrasonic transducer and realize the mutual conversion of signals between the ultrasonic transducer and the main control. TDC is a digital time conversion module that measures the time difference between the two signals based on the input sending and receiving signals and feeds back to the main control. The ultrasonic transducer realizes the mutual conversion between electrical signals and mechanical waves.

[0074] This embodiment is an aircraft hydraulic pipeline, measuring a stainless steel pipeline with a wall thickness of 1mm and a diameter of 8mm, red oil as the hydraulic medium, and an ultrasonic transducer of 7.5MHz. Specifically, the following steps are included:

[0075] Step 1: Collect static data and establish benchmark three-dimensional grid data. Connect the pipeline to a standard pressure generator with a range of 0 to 25 MPa, and place the pipeline in an incubator. Set the incubator temperature in the range of 0°C to 60°C, and set it as a temperature point every 5°C. After each temperature setting, wait for 2 hours for the pipeline temperature to stabilize before proceeding to the next step. At each temperature point, pressurize the pipeline pressure to 0MPa, 1MPa, 5MPa, 10MPa, 15MPa, 20MPa, and 25MPa, respectively. Each pressure point needs to wait until the temperature and pressure are constant, and collect the ultrasonic transit time value t.

[0076] Step 2: Collect data and calculate the conversion coefficient r between pressure and temperature. Fill the pipeline with hydraulic oil, close the pipeline, connect the pipeline to the pressure transmitter, and put them in a temperature box. Set the temperature of the temperature box in the range of 0℃ to 60℃, and set it as a temperature point every 5℃. After each temperature setting, wait for 2 hours for the pipeline temperature to stabilize, and read the pressure value Pn at each temperature point. Calculate a set of coefficients rn based on the recorded multiple sets of pressure points and temperature points, and take the average value as the final coefficient r.

[0077] Step 3: Collect pressure decay data and calculate the exponential decay coefficient k. Connect the pipeline to the pressure source and place it in the incubator. Set any temperature point and wait for 2 hours for the temperature to stabilize. Pressurize the pipeline to ΔP 加 Near the pressure point, close the stop valve (i.e., do not perform pressure compensation control) and record the pressure change curve over time within 5 minutes.

[0078] Let ΔP 衰 The pressure difference between the start and end of recording is summarized through multiple experiments: ΔP 衰 =α*ΔP 加 , where α is the proportional coefficient, and the pressure transformation ΔP, then α*ΔP pressure potential energy is converted into temperature internal energy, and α is between 0 and 1.

[0079] From the formula: ΔP = ΔT × r, we can get ΔT = ΔP 衰 / r, that is, the pressure decay curve can be expressed by the temperature decay curve, that is: ΔP(t) = ΔP 衰 / re -kt , combined with the pressure conversion curve data, the attenuation coefficient k value can be obtained by fitting the data through the least squares method.

[0080] Step 4: Calculate the liquid pressure value in the pipeline in real time based on the currently measured transit time Δt and temperature T. The formula is as follows:

[0081]

[0082] In the specific implementation process, the temperature sound velocity coefficient compensation method is used to subtract the sound velocity change caused by the temperature change from the measured sound velocity change, thereby obtaining the sound velocity change caused by the pressure change. The temperature sound velocity coefficient can be obtained through experiments.

[0083] c=αT 2 +βT+γ

[0084] Where c is the actual sound speed under atmospheric pressure, α, β, γ are the temperature sound speed coefficients, and T is the measured temperature.

[0085] The above specific implementation methods or cases are only used to explain the technical solutions of the present invention, and are not intended to limit the present application. Any parts not described in detail are deemed to be conventional technical means or common knowledge in the field. It can be understood by ordinary technicians in this field that: based on the design concept of the present application, the technical solutions recorded in the aforementioned implementation methods should be adaptively modified, or some or all of the technical features therein should be replaced by equivalents. These modifications, equivalent replacements, and adaptively improved technical solutions do not depart from the technical essence of the present invention and should all be covered within the protection scope of the present application.

Claims

1. An ultrasonic pressure measurement system for aircraft hydraulic pipelines, characterized in that: The measuring system comprises: a control module, a sending module, a receiving module, a data processing module, a first ultrasonic transducer, a second ultrasonic transducer, and a temperature sensor; The control module generates a complementary PWM wave of an ultrasonic driving signal, and drives and amplifies the first ultrasonic transducer to transmit an ultrasonic signal through the sending module. The control module synchronously sends a signal to the data processing module TDC for timing. The ultrasonic signal collected by the second ultrasonic transducer is converted into an electrical signal by the receiving module and sent to the control module. The control module also performs algorithm fusion processing on the signal processed by the DSP and the time of the data processing module, and displays it through the human-computer interaction module; The data processing module forms a three-dimensional array of transit time values ​​Δt at different temperatures and pressures; and solves the static pressure P at any temperature and transit time by bilinear interpolation. 静 ; The temperature sensor collects temperature signals in real time and converts them into electrical signals for transmission to the control module.

2. The aircraft hydraulic pipeline ultrasonic pressure measurement system according to claim 1, characterized in that: The data processing module performs median filtering on the two sets of measured time values ​​respectively, and also performs median filtering on the measured temperature value; the two time values ​​are fused by the Kalman fusion algorithm to obtain the final ultrasonic propagation time; The pressure value data corresponding to the propagation time and temperature stored in the system calibration data table is read, and the measured temperature and time values ​​are converted into the final pipeline liquid pressure value by using the bilinear interpolation method.

3. The aircraft hydraulic pipeline ultrasonic pressure measurement system according to claim 1, characterized in that: The data processing module includes an analog front-end unit, a digital TDC, and an arithmetic unit; the digital TDC is composed of a precision counter and a coarse value counter, and is responsible for converting the front-end effective signal into a unit time and transmitting it to the digital TDC; the arithmetic unit is used to calibrate the unit time stored in the digital TDC into a standard time related to the reference clock, and store it in the corresponding result register; The arithmetic unit processes the value counted by the digital TDC, calibrates the value of the digital TDC, saves the calibrated value to the corresponding result register and status register, and also accumulates the expected sum of the STOP signal and stores the accumulated value in the corresponding result register; The analog front end unit is responsible for signal conversion and transmission to the digital TDC. The analog front end is composed of a precision comparator, a programmable bias voltage generator, a first wave processor, and a high-speed switch. The analog front end can use digital signals and analog signals.

4. A method for measuring dynamic compensation of ultrasonic pressure in aircraft hydraulic pipelines, using the measurement system as claimed in claims 1 to 3, characterized in that: Construct a measurement model, place two ultrasonic transducers on both sides of the pipeline, one for signal transmission and the other for signal reception, process the transmitted and received signals, and calculate the ultrasonic propagation time; By measuring multiple groups of time values ​​at specified temperatures and specified pressures, a three-dimensional grid array is formed; by using bilinear interpolation, the temperature value and transit time value of the pipeline are measured to calculate the pressure value in the pipeline.

5. The method for dynamic compensation measurement of ultrasonic pressure in aircraft hydraulic pipelines according to claim 4, characterized in that: The following steps are involved: Step 1: Collect the transit time values ​​Δt at different temperatures and pressures to form a three-dimensional array; use bilinear interpolation to solve the static pressure P at any temperature and transit time. 静 ; Step 2: Calculate the conversion coefficient r between pressure and temperature; Step 3: Collect pressure decay data and calculate the exponential decay coefficient k; Step 4: Calculate the pressure value P of the liquid in the pipeline in real time according to the currently measured transit time Δt and temperature T.

6. The method for dynamic compensation measurement of ultrasonic pressure in aircraft hydraulic pipelines according to claim 5, characterized in that: Step 1: The collection and solution process is as follows: the pipeline is connected to a standard pressure generator with a range of 0 to 25 MPa, and the pipeline is placed in an incubator. The incubator temperature is set within the range of 0°C to 60°C, and a temperature point is set every 5°C. After each temperature setting is completed, it is necessary to wait for 2 hours for the pipeline temperature to stabilize before proceeding to the next step; at each temperature point, the pipeline pressure is pressurized to 0MPa, 1MPa, 5MPa, 10MPa, 15MPa, 20MPa, and 25MPa, respectively. At each pressure point, it is necessary to wait until the temperature and pressure are constant, and collect the ultrasonic transit time value Δt.

7. The method for dynamic compensation measurement of ultrasonic pressure in aircraft hydraulic pipelines according to claim 6, characterized in that: In step 2, fill the pipeline with hydraulic oil, seal the pipeline, connect the pipeline to the pressure transmitter, and put them in a thermostat together. Set the thermostat temperature in the range of 0℃ to 60℃, and set it as a temperature point every 5℃. After each temperature setting, wait for 2 hours for the pipeline temperature to stabilize, and read the pressure value Pn at each temperature point; calculate a set of coefficients rn based on the recorded multiple groups of pressure points and temperature points, and take their average value as the final coefficient r.

8. The method for measuring dynamic compensation of ultrasonic pressure in aircraft hydraulic pipelines according to claim 7, characterized in that: In step 3, connect the pipe to the pressure source and place it in the temperature box, set any temperature point, and wait for 2 hours for the temperature to stabilize; pressurize the pipe to ΔP 加 Near the pressure point, close the stop valve, do not perform pressure compensation control, and record the pressure change curve over time within 5 minutes; Let ΔP 衰 The pressure difference between the start and end of recording is summarized through multiple experiments: ΔP 衰 =α*ΔP 加 , where α is the proportional coefficient, and the pressure transformation ΔP, then α*ΔP pressure potential energy is converted into temperature internal energy, and α is between 0 and 1.

9. The method for measuring ultrasonic pressure dynamic compensation of aircraft hydraulic pipelines according to claim 8, characterized in that: In step 3, the attenuation coefficient k is solved as follows: From the formula ΔP=ΔT×r, we can get ΔT=ΔP 衰 / r, that is, the pressure decay curve can be expressed by the temperature decay curve, that is: ΔP(t) = ΔP 衰 / re -kt , combined with the pressure conversion curve data, the attenuation coefficient k value can be obtained by fitting the data through the least squares method.

10. The method for dynamic compensation measurement of ultrasonic pressure in aircraft hydraulic pipelines according to claim 8, characterized in that: In step 4, the formula for solving the pressure value P of the liquid in the pipeline is as follows: The temperature sound velocity coefficient compensation method is adopted to subtract the sound velocity change caused by temperature change from the measured sound velocity change, so as to obtain the sound velocity change caused by pressure change; the temperature sound velocity coefficient is obtained through experiments; c=αT 2 +βT+γ Where c is the actual sound speed under atmospheric pressure, α, β, γ are the temperature sound speed coefficients, and T is the measured temperature.

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