Method for determining explosion pressure of PVDF piezoelectric sensor in current mode

Abstract

The invention is suitable for the technical field of explosion pressure measurement, and provides a method for determining the explosion pressure of a PVDF piezoelectric sensor in a current mode, and the method comprises the steps: carrying out the discrete sampling of a voltage signal outputted by an oscilloscope, and obtaining a plurality of sampling voltage signals; filtering the sampled voltage signal by using a filter so as to filter out a low-frequency trend term, drift noise and background noise introduced by sampling, and calculating explosion pressure corresponding to a sampling point based on the filtered voltage signal; generating an explosion pressure curve based on the explosion pressure corresponding to the plurality of sampling points, and judging whether the explosion pressure curve meets a preset filtering termination condition or not; if yes, taking the explosion pressure corresponding to each sampling point as the explosion pressure of the explosive at the time corresponding to the sampling point; and if not, adjusting the filtering frequency of the filter, and continuing to filter the sampling voltage signal corresponding to the sampling point by using the filter until a filtering termination condition is met. According to the invention, the measurement precision of the explosive pressure can be improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of explosion pressure measurement, and particularly relates to a method for determining explosion pressure in a current mode of a PVDF piezoelectric sensor. BACKGROUND

[0002] Polyvinylidene fluoride (PVDF) piezoelectric sensors have been widely used in transient high-pressure testing scenarios such as explosion mechanics, impact loading, and structural dynamic response due to their good flexibility, fast response, and impact resistance. In particular, in explosion load measurement, the PVDF sensor converts the force process into a charge signal through the positive piezoelectric effect, and then converts it into a current or voltage form through a circuit to identify the pressure process of the detonation wave and the explosion gas. With the improvement of sensor integration and measurement frequency, the current mode has gradually become a common means for high-bandwidth and high-sensitivity measurement. However, in actual explosion testing, due to strong environmental electromagnetic interference, wide signal frequency coverage, and difficulty in system impedance matching, low-frequency trend items, drift noise, and background noise are easily introduced in the process of discrete sampling and processing of the voltage signal recorded by the oscilloscope, which seriously affects the accuracy of the pressure curve obtained by subsequent integral calculation.

[0003] Most existing methods directly integrate the voltage to restore the pressure, but when facing voltage signals with low-frequency trend items, drift noise, and background noise, integral error accumulation occurs, causing distortion of the pressure curve, and even the peak pressure and sustained pressure stages cannot be accurately identified. Although some studies introduce sliding window, envelope analysis and other algorithms for trend item suppression, there are still problems such as peak loss and signal distortion in high dynamic and transient processes, resulting in low measurement accuracy of explosive explosion pressure. SUMMARY

[0004] The embodiments of the application provide a method for determining explosion pressure in a current mode of a PVDF piezoelectric sensor, which can solve the problem of low measurement accuracy of explosive explosion pressure.

[0005] The embodiments of the application provide a method for determining explosion pressure in a current mode of a PVDF piezoelectric sensor, which can solve the problem of low measurement accuracy of explosive explosion pressure. discretely sample the voltage signal output by the oscilloscope to obtain a plurality of sampling voltage signals corresponding to a plurality of sampling points; The filter is used for filtering low-frequency trend items, drift noise and background noise introduced by discrete sampling. The explosion pressure curve is generated based on the explosion pressures corresponding to the plurality of sampling points, and it is determined whether the explosion pressure curve satisfies a preset filter termination condition. If the explosion pressure curve satisfies the filter termination condition, the explosion pressure corresponding to each sampling point is taken as the explosion pressure of the explosive at the time corresponding to the sampling point. If the explosion pressure curve does not satisfy the filter termination condition, the filter frequency is adjusted, and the step of filtering the sampling voltage signal corresponding to each sampling point by using the filter and calculating the explosion pressure corresponding to the sampling point based on the filtered voltage signal is returned.

[0006] Optionally, the calculation of the explosion pressure corresponding to the sampling point based on the filtered voltage signal comprises: The explosion pressure corresponding to the sampling point is calculated by using a pressure calculation formula. ; Wherein, Pn represents the explosion pressure corresponding to the nth sampling point, Pn-1 represents the explosion pressure corresponding to the (n-1)th sampling point, is 0, R represents the resistance value of the parallel resistor, T represents the sampling interval of the discrete sampling, A represents the effective area of the PVDF piezoelectric sensor, d33 represents the piezoelectric constant, Vn represents the voltage value of the filtered voltage signal corresponding to the nth sampling point, Vn-1 represents the voltage value of the filtered voltage signal corresponding to the (n-1)th sampling point.

[0007] Optionally, the explosion pressure curve is a curve of the explosion pressure of the explosive versus time. The filter termination condition comprises: The explosion pressure curve contains the explosion pressure corresponding to a first time period in which the explosion of the explosive generates a detonation wave; The explosion pressure curve contains the explosion pressure corresponding to a second time period in which the explosion of the explosive generates detonation gas; The descending rate of the explosion pressure after the second time period satisfies: ; The explosion pressure curve satisfies:​​​​ ; wherein, represents the falling rate of the explosion pressure at the i th sampling point, represents a falling rate threshold, represents the explosion pressure corresponding to the i th sampling point, represents a residual fluctuation noise threshold, represents the explosion pressure corresponding to the i th sampling point, represents the explosion pressure corresponding to the i th sampling point, represents a preset explosion test time, represents a pressure average value calculated based on the voltage signal output by the oscilloscope within a preset time period before the explosion of the explosive. Optionally, the length of the first time period is 200 microseconds to 500 microseconds, and the length of the second time period is 20 milliseconds to 100 milliseconds.

[0008] Optionally, the thickness of the PVDF piezoelectric sensor is 10 μm to 50 μm, and the diameter of the PVDF piezoelectric sensor is less than or equal to 5 mm.

[0009] Optionally, the sampling frequency of the discrete sampling is greater than or equal to 10 MHz.

[0010] Optionally, the filter is a Butterworth high-pass filter.

[0011] Optionally, the diameter of the explosion hole is greater than 50 mm.

[0012] The above scheme of the present application has the following beneficial effects: In the embodiments of the present application, after the voltage signal output by the oscilloscope is discretely sampled, the original voltage signal is iteratively filtered by using a filter, the low-frequency trend item, drift noise and background noise introduced by the discrete sampling are suppressed, and the high-frequency effective signal generated in the explosion shock wave and the action process of the explosion gas are retained, so that the explosion pressure of the explosive calculated based on the voltage signal after the iterative filtering has higher precision than the explosion pressure determined by the traditional current mode, and the effect of improving the measurement precision of the explosion pressure of the explosive is achieved.

[0013] Other beneficial effects of the present application will be described in detail in the subsequent specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0014]

[0015] ​​In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description only some of the embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0016] Figure 1 The schematic diagram of the explosion pressure measurement circuit in the related art is shown in FIG. 1. Figure 2 The flow chart of the method for determining the explosion pressure in the current mode of the PVDF piezoelectric sensor provided by an embodiment of the present application is shown in FIG. 2. Figure 3 The schematic diagram of the original voltage signal in an example of the present application is shown in FIG. 3. Figure 4 The schematic diagram of the explosion pressure curve in an example of the present application is shown in FIG. 4. DETAILED DESCRIPTION

[0017] In the following description, specific details are set forth in order to provide a thorough understanding of embodiments of the present application. However, persons having ordinary skill in the art will appreciate that embodiments of the present application can be practiced without the specific details, and that the present application is not limited to the specific details or the particular order described herein. Well-known structures, devices, circuits, and methods have not been described in detail so as not to obscure the description of the present application.

[0018] It should be understood that the term "comprises" when used in this specification and the appended claims specifies the presence of stated features, integers, steps, operations, elements, and / or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0019] It should also be understood that the term "and / or" when used in this specification and the appended claims, such as in the case of "A and / or B", is intended to mean an "A or B" or "A and B", that is, A and / or B is intended to cover the case where at least one of the items is present and the case where both of the items are present.

[0020] As used in this specification and the appended claims, the term "if" can be construed to mean "when" or "once" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrase "if it is determined" or "if [a described condition or event] is detected" can be construed to mean "once it is determined" or "in response to determining" or "once [the described condition or event] is detected" or "in response to detecting [a described condition or event]", depending on the context.

[0021] In addition, in the description of the present application and the appended claims, the terms "first", "second", "third", etc. are used only to distinguish descriptions and cannot be understood as indicating or implying relative importance.

[0022] Reference to "one embodiment" or "some embodiments" or "one implementation" or "some implementations" described in the present application means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present application. Thus, the appearance of the phrases "in one embodiment", "in some embodiments", "in other some embodiments", "in some other embodiments" and the like in various places in the specification is not necessarily all referring to the same embodiment, but means "one or more but not all embodiments", unless otherwise specifically stated. The terms "include", "contain", "have" and their variants mean "including but not limited to", unless otherwise specifically stated.

[0023] In view of the low measurement accuracy of the explosive explosion pressure at present, the present application provides a method for determining the explosion pressure of a PVDF piezoelectric sensor in current mode, which, after the voltage signal output by the oscilloscope is discretely sampled and processed, uses a filter to iteratively filter the original voltage signal, suppresses the low-frequency trend item, drift noise and background noise introduced by discrete sampling, and retains the high-frequency effective signal generated during the action of the explosion shock wave and the explosion gas, so that the explosion pressure of the explosive calculated based on the voltage signal after iterative filtering is more accurate than the explosion pressure determined by the traditional current mode, and the effect of improving the measurement accuracy of the explosion pressure of the explosive is achieved.

[0024] The method for determining the explosion pressure of a PVDF piezoelectric sensor in current mode provided by the present application will be described below in conjunction with specific embodiments.

[0025] In the related art, the measurement of the explosion pressure of the explosive in the current mode of the PVDF piezoelectric sensor is realized, and the structure of the explosion pressure measurement circuit composed of the PVDF piezoelectric sensor, the related parallel resistance and the oscilloscope is as shown in Figure 1 . Figure 1 In the above structure, PVDF represents the PVDF piezoelectric sensor, R represents the parallel resistance of the PVDF piezoelectric sensor, U represents the voltage signal measured by the oscilloscope, represents the current corresponding to the charge signal output by the PVDF piezoelectric sensor.

[0026] It can be understood that, in the explosion pressure measurement of the explosive, the PVDF piezoelectric sensor is arranged on the inner wall of the explosion hole in which the explosive (i.e., the explosive to be measured for explosion pressure) is arranged, and the output end of the PVDF piezoelectric sensor is connected in parallel with a parallel resistor and an oscilloscope in sequence. During the explosion of the explosive, the output end of the PVDF piezoelectric sensor outputs a charge signal, and the output charge signal is converted into a current signal through the parallel resistor and is recorded as a voltage signal through the high-impedance oscilloscope.

[0027] In some optional embodiments, the above-mentioned PVDF piezoelectric sensor can be attached to the inner wall of the explosion hole, and specifically can be installed on the inner wall of the explosion hole containing water or air medium. Specifically, the thickness of the PVDF piezoelectric sensor can be 10 μm to 50 μm, and the diameter of the PVDF piezoelectric sensor is less than or equal to 5 mm, so as to meet the constraint conditions of hole wall attachment and curvature, and thus be suitable for explosion pressure measurement.

[0028] In order to facilitate the development of explosion test, the hole diameter of the above-mentioned explosion hole is greater than 50 mm, so as to be suitable for the test of the explosive charge structure with a hole diameter greater than 50 mm. It can be understood that the charge form can be an air uncoupling or water uncoupling structure, and the attachment position of the PVDF piezoelectric sensor is the inner wall surface of the hole wall.

[0029] Based on the foregoing explosion pressure measurement circuit, as shown in Figure 2 The determination method of the explosion pressure of the PVDF piezoelectric sensor in the current mode provided by the embodiments of the present application includes the following steps: Step 21, discrete sampling is performed on the voltage signal output by the oscilloscope to obtain a sampling voltage signal corresponding to a plurality of sampling points.

[0030] Each sampling point corresponds to a time point in the explosion test process, and the sampling voltage signal corresponding to each sampling point is the voltage signal output by the oscilloscope at the corresponding time point. In some embodiments of the present application, the input impedance of the above-mentioned oscilloscope is greater than 1 MΩ, and the sampling frequency of the above-mentioned discrete sampling is greater than or equal to 10 MHz, so as to ensure the transient response capability of voltage sampling. At the same time, since the sampling frequency is high enough, the explosion pressure corresponding to all sampling points in the subsequent steps can be regarded as covering the explosion pressure at each time point (i.e., each time point in the explosion test process), so as to ensure the accuracy of the explosion pressure of the explosive.

[0031] Step 22, for each sampling point in the plurality of sampling points, a filter is used to filter the sampling voltage signal corresponding to the sampling point, and the explosion pressure corresponding to the sampling point is calculated based on the filtered voltage signal; the filter is used to filter out the low-frequency trend item, drift noise and background noise introduced by discrete sampling.

[0032] The aforementioned low-frequency trend term, drift noise, and background noise are introduced during the discrete sampling of the voltage signal output by the oscilloscope. For the... For each sampling point, the corresponding sampling voltage signal exist: , Indicates the first The actual sampled voltage signal (i.e., the voltage signal excluding noise) corresponding to each sampling point. Indicates the first The slow changing trends corresponding to each sampling point (i.e., low-frequency trend term, drift noise, and background noise). Specifically, the low-frequency trend term refers to the slowly changing, non-periodic offset component in the pressure signal, manifested as a gradual increase or decrease in the entire curve over time, rather than actual fluctuations from the physical processes of the explosion. Drift noise refers to slow-changing random noise with non-zero mean caused by instability defects in the explosion pressure measurement circuit; unlike the "deterministic" gradual change of the low-frequency trend term, it is more irregular and unstable. Background noise specifically refers to the widespread non-target noise component in the voltage signal that is unrelated to the explosion, characterized by high frequency, low amplitude, near-white noise, or narrowband noise.

[0033] To improve the accuracy of the explosion pressure, this application utilizes a filter to denoise the sampled voltage signal, suppressing low-frequency trend terms, drift noise, and background noise introduced by discrete sampling, while retaining the high-frequency effective signals generated during the explosion shock wave and the action of the explosive gases. To effectively filter out low-frequency trend terms, drift noise, and background noise, and retain the high-frequency effective components, the filter cutoff frequency is set to above 10 kHz.

[0034] It should be noted that the above filter can be a Butterworth high-pass filter, specifically a fourth-order IIR filter, designed as a bidirectional zero-phase filter to avoid phase distortion. In some optional embodiments, the filter function can be implemented using Python to generate the fourth-order filter coefficients and the `filtfilt` function (a bidirectional zero-phase filter function, a tool for implementing zero-phase-shift filtering) can be used to achieve bidirectional filtering.

[0035] In some embodiments of this application, the specific implementation of calculating the explosion pressure corresponding to the sampling point based on the filtered voltage signal can be as follows: The explosion pressure corresponding to the sampling point is calculated using the following pressure calculation formula: ; in, Indicates the first The explosion pressure corresponding to each sampling point Indicates the first The explosion pressure corresponding to each sampling point is 0, represents the resistance value of the parallel resistance, represents the sampling interval of the discrete sampling, represents the effective area of the PVDF piezoelectric sensor (usually refers to the force area of the piezoelectric element), represents the piezoelectric constant (the piezoelectric constant is a constant related to the piezoelectric sensor material, with units of picocoulombs per Newton (pC / N)), represents the voltage value of the filtered voltage signal corresponding to the i-th sampling point, represents the voltage value of the filtered voltage signal corresponding to the i-th sampling point, represents the voltage value of the filtered voltage signal corresponding to the i-th sampling point. It is worth mentioning that in the above pressure calculation formula, the midpoint method is used to approximate the integral of the voltage signal, and the voltage in the integral interval is the average of the adjacent two points, so the calculation accuracy can be improved and the sampling error can be reduced.

[0036] Step 23, based on the explosion pressure corresponding to a plurality of sampling points, an explosion pressure curve is generated, and it is judged whether the explosion pressure curve satisfies a preset filtering termination condition, if the explosion pressure curve satisfies the filtering termination condition, step 24 is executed, if the explosion pressure curve does not satisfy the filtering termination condition, step 25 is executed.

[0037] As described above, since the frequency of discrete sampling is high enough, explosion pressure curve can be generated based on the explosion pressure corresponding to a plurality of sampling points (specifically, the curve can be generated by using common drawing tools), which is the relationship curve between explosion pressure of explosive and time, recording the explosion pressure corresponding to each time in the explosion test process.

[0038] In some embodiments of the present application, the above filtering termination condition includes:

[0039] the explosion pressure curve contains the explosion pressure corresponding to the first time period when the detonation wave is generated by the explosion of the explosive; the explosion pressure curve contains the explosion pressure corresponding to the second time period when the detonation gas is generated by the explosion of the explosive; the descending rate of the explosion pressure after the second time period satisfies: ; the explosion pressure curve satisfies: .

[0040] wherein, represents the descending rate of the explosion pressure at the i-th sampling point (approximately the pressure difference between adjacent two sampling points divided by the time interval, with units of MPa / ms), represents the descending rate threshold, such as 5 MPa / ms, represents the explosion pressure corresponding to the i-th sampling point, ​​​represents a residual fluctuation noise threshold, such as 2 MPa, represents a time point in the explosion pressure curve corresponding explosion pressure, represents a preset explosion test time (the preset time is usually greater than the total duration of the explosion of the explosive, and can be set according to actual conditions), represents a pressure average value calculated based on the voltage signal output by the oscilloscope within a preset period before the explosion of the explosive. It should be noted that before the explosion of the explosive, the PVDF piezoelectric sensor also outputs current, and therefore the oscilloscope outputs voltage. The calculation method of the pressure within the preset period before the explosion of the explosive is the same as that of steps 21 and 22 described above, that is, the voltage signal output by the oscilloscope within the preset period is first discretely sampled, then the pressure corresponding to each discrete sampling point is calculated, and finally the average value of the pressures is taken as .

[0041] The duration of the first time period is 200 microseconds to 500 microseconds, and the duration of the second time period is 20 milliseconds to 100 milliseconds.

[0042] In related technologies, based on the explosion crushing mechanism, the explosive will generate a detonation wave and an explosion gas in the explosion process. Therefore, the explosion pressure curve must contain the detonation wave stage (i.e., the first time period and the explosion pressure corresponding to the first time period described above) and the explosion gas stage (i.e., the second time period and the explosion pressure corresponding to the second time period described above).

[0043] The detonation wave stage has the following characteristics: voltage rises sharply, explosion pressure jumps instantaneously, and reflects the shock wave characteristics in the initial stage of initiation of the explosive. That is, at a certain time T1 after initiation, a transient high-amplitude peak pressure P1 is generated, representing the loading of the detonation wave; generally, the first explosion pressure peak is around 50 microseconds, and the entire stage can be up to 500 microseconds, and the result is not unique, and is related to the properties and amount of the explosive.

[0044] The explosion gas stage has the following characteristics: the explosion pressure starts to appear a second significant platform segment at time T2 (T2 is after the detonation wave stage), the explosion pressure reaches P2, and the duration is significantly longer than that of the detonation wave stage, which can be judged as the loading effect of the explosion gas expansion. In this stage, the voltage is flat but significant, the explosion pressure is platform-like, reflecting the dominant sustained loading effect of gas expansion.

[0045] It should be noted that when the decline rate of the explosion pressure curve after the second time period satisfies: , it means that there is no significant explosion pressure signal, and the curve is in the natural decay stage, and the integration can be terminated. The explosion pressure curve satisfies: If the filtered curve does not appear to be baseline-shifted, the residual low-frequency trend term, drift noise and background noise are completely removed.

[0046] Step 24: Taking the explosion pressure corresponding to each sampling point as the explosion pressure of the explosive at the time corresponding to the sampling point.

[0047] Step 25: Adjusting the filtering frequency of the filter, and returning to the step of filtering the sampling voltage signal corresponding to each sampling point in the plurality of sampling points by using the filter, and calculating the explosion pressure corresponding to the sampling point based on the filtered voltage signal.

[0048] In some embodiments of the present application, the filter is implemented based on the Python language, and usually needs to be filtered multiple times to determine the explosion pressure of the explosive at each time.

[0049] Specifically, when the explosion pressure curve does not meet the filtering termination condition after being filtered once, the filtering frequency of the filter is adjusted (specifically, the filtering frequency needs to be adjusted up or down according to the explosion pressure curve), and the adjusted filter is used to return to Step 22 until the explosion pressure curve meets the filtering termination condition, and the explosion pressure of the explosive at the time corresponding to each sampling point is obtained.

[0050] It can be understood that, in order to facilitate the user to view the explosion pressure, the determined explosion pressure can be displayed to the user in the form of presenting the explosion pressure curve.

[0051] It is worth mentioning that, the determination method of the present application processes the original voltage signal by using a fourth-order Butterworth high-pass filter to remove the low-frequency trend term, drift noise and background noise, and constructs a pressure calculation formula according to the piezoelectric effect and the physical model under the current mode, so as to realize high-precision reconstruction of the explosion pressure signal. Therefore, the present application can effectively suppress noise interference, improve the precision and stability of explosion pressure measurement, and is suitable for explosion load test scenes in water or air medium hole walls, and is especially suitable for processing and identification of transient high-frequency impact signals.

[0052] More worth mentioning is that, after accurately obtaining the full-time explosion pressure response curve (i.e. the aforementioned explosion pressure curve) without drift and with high signal-to-noise ratio, the pressure peak characteristics of the explosive can be regulated and controlled according to the full-time explosion pressure response curve, the action time of the detonation wave and the detonation gas is reasonably allocated, and the time-domain optimization control of the explosion energy is realized, so as to significantly improve the fine level of blasting parameter design, and help to improve the blasting effect, reduce the disturbance of rock mass, and enhance the precision of explosion control.

[0053] For the sake of understanding, the origin of the aforementioned pressure calculation formula is exemplarily described as follows.

[0054] Suppose that a PVDF piezoelectric sensor is subjected to force , the free surface charge density is generated in the polarization direction , which satisfies: ; In the above formula, represents the piezoelectric constant, with the unit of picocoulomb per Newton (pC / N), represents the effective area of the PVDF piezoelectric sensor, represents the instantaneous normal stress / pressure in the time domain, represents the time-varying charge quantity. The output charge of the PVDF piezoelectric sensor is converted into a current signal through an external parallel resistor: ; In the above formula, represents the current output by the PVDF piezoelectric sensor, with the unit of A, represents the derivative of stress with respect to time, with the unit of Pa / s. An oscilloscope collects the signal in a high-impedance input mode and records the equivalent voltage , which is related to the current flowing through the resistor as follows: ; In the above formula, represents the voltage recorded by the oscilloscope, with the unit of V, represents the resistance value of the parallel resistor.

[0055] The above formula is rearranged to obtain the relationship between the original pressure and the voltage as follows: ; In the above formula, represents the integral constant, which can be taken as 0 under ideal noise-free conditions. However, in practice, there are baseline drift and low-frequency errors, which cause trend errors in the integral result, resulting in inaccurate estimation of the explosion pressure

[0056] Next, a discrete integral model is established: the sampling frequency is fs, the time step Δt = 1 / fs, and the voltage signal at the discrete time is represented as Vn. The pressure is numerically integrated as follows: ; In the above formula, represents the explosion pressure value corresponding to the nth sampling point, with the unit of Pa; represents the serial number of the sampling point, represents the voltage signal corresponding to the nth sampling point, represents the voltage signal corresponding to the nth sampling point, represents the voltage signal corresponding to the nth sampling point, ​​The voltage signal corresponding to each sampling point, where Δt represents the sampling time interval in seconds.

[0057] It should be noted that the pressure calculation formula mentioned above is a variation of the above formula, one using a summation operation and the other using an accumulation operation.

[0058] To facilitate understanding of the determination method provided in this application, a specific example is provided below to illustrate the determination method of this application.

[0059] In this example, a PVDF piezoelectric sensor was attached to the inner wall of a test blast borehole with a diameter of 90 mm and a depth of 4 m, fixed in place and kept in close contact with the borehole wall. The sensor thickness was 30 μm to ensure it did not affect the borehole wall curvature and pressure propagation. A coaxial cable was used to complete the transmission channel setup, and the signal entered an oscilloscope with a sampling frequency set to 10 MHz and a sampling time window of 100 ms. The detonating charge was a 32 mm diameter rock emulsion explosive, approximately 0.25 m from the measuring point, using a decoupled charge structure. After setting up the blast pressure measurement circuit, the raw voltage data in PVDF current mode was acquired. Due to the presence of a strong low-frequency trend term, drift noise, and background noise in the system, the raw voltage signal (i.e., the voltage signal output by the oscilloscope) was as follows: Figure 3 As shown, direct integration will produce baseline drift error. Figure 3 The horizontal axis represents time in milliseconds (ms), and the vertical axis represents the test voltage (i.e., the voltage value of the original voltage signal) in volts (V). Therefore, this application uses Python to implement a fourth-order Butterworth high-pass filter, setting the cutoff frequency to above 10 kHz. The filter coefficients are generated using Python, and the `filtfilt` function is used to implement bidirectional zero-phase filtering, resulting in the filtered voltage signal sequence.

[0060] Next, based on the integral relationship between the PVDF piezoelectric model and the current mode, the pressure-time response curve is calculated. The differential integral expression is used: ; in: =50 Ω, d = 10 pC / N, Δt = 0.1 μs. The integrated explosion pressure curve is shown below. Figure 4 As shown, it is clearly divided into the detonation wave stage and the explosive gas stage. For example... Figure 4 As shown, the detonation wave stage is a steep rise region dominated by the detonation wave, with a pressure peak of P1=165 MPa appearing around time T1=0.12 ms, exhibiting typical impact response characteristics; the explosive gas stage is the explosive gas loading stage, with a plateau pressure peak of P2=157 MPa appearing at T2=9.80 ms, showing a stable and continuous action state. Figure 4The horizontal axis represents time in ms, and the vertical axis represents explosion pressure in MPa.

[0061] In summary, the method for determining explosion pressure in the current mode of the PVDF piezoelectric sensor has the following advantages: I. The original voltage signal in the current mode of the PVDF piezoelectric sensor is processed using a fourth-order Butterworth high-pass filter, which can effectively remove low-frequency trend items, drift noise and background noise, significantly improve the signal-to-noise ratio of the pressure signal, and solve the baseline drift problem caused by cumulative error in the existing integral method.

[0062] II. A termination judgment mechanism based on integral expression and physical segmentation identification is proposed, which can accurately identify the peak pressure and stable pressure interval of the detonation wave phase and the detonation gas phase.

[0063] III. The proposed method is based on a strict piezoelectric physical model and mathematical integral relationship, and has good portability and universality, which can adapt to PVDF piezoelectric sensors of different sizes and thicknesses, and is suitable for explosion load test scenarios of air medium or water-containing medium hole wall.

[0064] IV. The method has good dynamic response capability for the whole process of explosion pressure, and can accurately capture the peak value of the detonation wave (microsecond order) and the pressure platform of the detonation gas (millisecond order) at the same time, providing a reliable data basis for blasting energy distribution analysis, charge structure optimization and rock mass response evaluation.

[0065] V. Compared with the existing noise reduction methods based on moving average and empirical windowing, the present application retains high-frequency effective signals, filters out noise without excessively weakening the peak value, effectively balances signal integrity and processing stability, and is suitable for integration in the data acquisition and real-time processing module of the explosion mechanics test system.

[0066] The above is the preferred embodiment of the present application. It should be noted that for ordinary skilled persons in the technical field, some improvements and refinements can be made without departing from the principles described in the present application, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method for determining the explosion pressure in current mode using a PVDF piezoelectric sensor, characterized in that, A PVDF piezoelectric sensor is installed on the inner wall of an explosive hole containing explosives. A parallel resistor and an oscilloscope are connected in parallel to the output of the PVDF piezoelectric sensor. During the explosive detonation, the output of the PVDF piezoelectric sensor outputs a charge signal. The method for determining the explosion pressure in the current mode of the PVDF piezoelectric sensor includes: The voltage signal output by the oscilloscope is discretely sampled to obtain sampled voltage signals corresponding to multiple sampling points; For each of the plurality of sampling points, a filter is used to filter the sampling voltage signal corresponding to the sampling point, and the explosion pressure corresponding to the sampling point is calculated based on the filtered voltage signal; the filter is used to filter out low-frequency trend terms, drift noise and background noise introduced by the discrete sampling. An explosion pressure curve is generated based on the explosion pressure corresponding to the multiple sampling points, and it is determined whether the explosion pressure curve meets the preset filtering termination condition. If the explosion pressure curve satisfies the filtering termination condition, then the explosion pressure corresponding to each sampling point is taken as the explosion pressure of the explosive at the time corresponding to that sampling point. If the explosion pressure curve does not meet the filtering termination condition, the filtering frequency of the filter is adjusted, and the process returns to the steps of filtering the sampling voltage signal corresponding to each of the plurality of sampling points using the filter, and calculating the explosion pressure corresponding to the sampling point based on the filtered voltage signal.

2. The method for determining the explosion pressure in current mode using a PVDF piezoelectric sensor according to claim 1, characterized in that, The calculation of the explosion pressure corresponding to the sampling point based on the filtered voltage signal includes: The explosion pressure corresponding to the sampling point is calculated using a pressure calculation formula; the pressure calculation formula is: ； in, Indicates the first The explosion pressure corresponding to each sampling point Indicates the first The explosion pressure corresponding to each sampling point =0, This indicates the resistance value of the parallel resistor. This represents the sampling interval of the discrete sampling. This indicates the effective area of ​​the PVDF piezoelectric sensor. Represents the piezoelectric constant. Indicates the first The voltage value of the filtered voltage signal corresponding to each sampling point. Indicates the first The voltage value of the filtered voltage signal corresponding to each sampling point.

3. The method for determining the explosion pressure in current mode using a PVDF piezoelectric sensor according to claim 1, characterized in that, The explosion pressure curve is the relationship curve between the explosion pressure of the explosive and time. The filtering termination conditions include: The explosion pressure curve includes the explosion pressure during the first time period when the detonation wave is generated by the explosion of the explosive; The explosion pressure curve includes the explosion pressure during the second time period when the explosive gases are generated during the explosion. After the second time period, the rate of decrease in explosion pressure satisfies: ; The explosion pressure curve satisfies: ; in, Indicates the first The rate of decrease of explosion pressure at each sampling point, Indicates the descent rate threshold. Indicates the first The explosion pressure corresponding to each sampling point Indicates the residual fluctuation noise threshold. Indicates the moment in the explosion pressure curve The corresponding explosion pressure, This indicates the preset explosion test time. This represents the average pressure calculated based on the voltage signal output by the oscilloscope during a preset time period before the explosive detonation.

4. The method for determining the explosion pressure in current mode using a PVDF piezoelectric sensor according to claim 3, characterized in that, The duration of the first time period is 200 microseconds to 500 microseconds, and the duration of the second time period is 20 milliseconds to 100 milliseconds.

5. The method for determining the explosion pressure in current mode using a PVDF piezoelectric sensor according to claim 1, characterized in that, The thickness of the PVDF piezoelectric sensor is 10μm to 50μm, and the diameter of the PVDF piezoelectric sensor is less than or equal to 5mm.

6. The method for determining the explosion pressure in current mode using a PVDF piezoelectric sensor according to claim 1, characterized in that, The sampling frequency of the discrete sampling is greater than or equal to 10 MHz.

7. The method for determining the explosion pressure in current mode using a PVDF piezoelectric sensor according to claim 1, characterized in that, The filter is a Butterworth high-pass filter.

8. The method for determining the explosion pressure in current mode using a PVDF piezoelectric sensor according to claim 1, characterized in that, The diameter of the explosion hole is greater than 50 mm.

Images