A system and method for measuring the internal ballistic velocity based on the magnetic induction intensity

Abstract

The application relates to an internal ballistic velocity testing system and method, in particular to an internal ballistic velocity testing system and method based on magnetic induction intensity, which solves the problems of the existing testing method, complex installation and use of the testing system based on the testing method, high testing cost and low testing precision. The system comprises an internal ballistic velocity generating system, a signal measurement and acquisition system and a data analysis processing and velocity calculation module; the internal ballistic velocity generating system comprises a loading system and a magnetic projectile; the magnetic projectile is installed in a launching tube of the loading system; the signal measurement and acquisition system comprises S sensors arranged on the outer tube wall of the launching tube in the axial direction and a data acquisition system; the input end of the data acquisition system is connected with the output end of the sensor, the output end of the data acquisition system is connected with the input end of the data analysis processing and velocity calculation module; the data analysis processing and velocity calculation module is used for filtering and denoising processing of the magnetic induction intensity signal and correlation analysis, and the internal ballistic velocity is calculated.

Description

Technical Field

[0001] This invention relates to an internal ballistic velocity testing system and method, and particularly to an internal ballistic velocity testing system and method based on magnetic induction intensity. Background Technology

[0002] To improve the launching performance of the loading system, closed-loop verification of internal ballistic calculation and testing is required to correct the internal ballistic calculation model, thereby making the verification of launching velocity and structural strength more accurate. Therefore, conducting internal ballistic velocity tests on the launching component is a necessary step to verify the validity of the internal ballistic calculation model and its results. Since the launching tube is circumferentially closed when the launching component moves within the loading system, ordinary high-speed cameras and other testing equipment are difficult to apply. Therefore, the corresponding internal ballistic velocity can only be obtained through methods such as laser Doppler velocimetry, the placement of inductive sensors on the outer wall of the tube, or the placement of accelerometers on the launching component.

[0003] When obtaining the corresponding internal ballistic velocity using laser Doppler velocimetry, the method requires the design of a specialized signal acquisition structure and experimental device. In particular, high-end and precise acquisition equipment and data processing devices are needed to capture optical signals, which is very costly.

[0004] In the existing technology, there are two main methods for obtaining the corresponding internal ballistic velocity by deploying induction sensors on the outer wall of the pipe: one is the strain gauge testing method, and the other is the pressure sensor testing method.

[0005] The strain gauge-based testing method involves placing strain gauges at regular intervals on the outer wall of the launching tube of a loading system. This monitors and measures the circumferential strain of the tube wall caused by the movement of the internal launching component during launch, obtaining the internal ballistic pressure changes under typical test conditions. The relationship between the displacement and the pressure at the base of the launching component during its movement is then derived, leading to the velocity of the launching component at different positions within the launching tube. However, the accuracy of strain gauge-based pressure testing is affected by various factors, such as the quality of the strain gauges, the installation method, and environmental conditions. Firstly, strain gauges are typically designed and manufactured based on the strain characteristics of specific materials, making installation and use relatively complex; proper installation and connection require certain operational skills. Secondly, changes in the external environment, such as temperature variations, humidity, vibration, or electromagnetic interference, can affect the performance of the strain gauges and the measurement results. Furthermore, since the launching tube wall of a loading system is usually circular, the surface flatness can affect the adhesion of the strain gauges and the transmission of strain signals, especially during low-speed movement when the deformation of the tube wall is very limited due to the low pressure at the base of the launching component, making effective measurement difficult.

[0006] The pressure sensor-based testing method involves deploying multiple pressure sensors on the outer wall of the launch tube of the loading system to rapidly acquire pressure sensor signals. These signals are then used to determine the arrival time of the launcher, and combined with the distance measured by the pressure sensors, the velocity of the launcher at different positions within the launch tube can be calculated. The limitation of this method is that it requires machining mounting holes for the pressure sensors into the tube wall, which disrupts the original structure of the tube and affects the overall structural strength and service life of the loading system. Furthermore, it is difficult to drill holes in the tube wall throughout the entire internal ballistic trajectory.

[0007] In existing technologies, the main method for obtaining the corresponding internal ballistic velocity by deploying acceleration sensors on the launcher is onboard velocity measurement. For hypersonic loading systems, onboard velocity measurement has several drawbacks. First, the launcher is usually small, making it difficult to install sensors on it. Second, the sensors themselves are expensive; if installed on the internal launcher, they will be damaged after a single use. Therefore, using this method for testing is very costly.

[0008] Therefore, there is an urgent need to develop an internal ballistic velocity testing system and method that is easy to install and use, does not affect the overall structural strength and service life of the loading system, has low testing costs, and can achieve high-precision and effective testing. This will enable accurate testing of internal ballistic velocity, thereby accurately correcting the internal ballistic calculation model, making the launch velocity and structural strength verification more accurate, and improving the launch performance of the loading system. Summary of the Invention

[0009] The purpose of this invention is to solve the technical problems of existing internal ballistic velocity testing methods, such as the complexity of the installation and use of the testing system, the impact of installation on the overall structural strength and service life of the loading system, high testing costs, low testing accuracy, and the inability to achieve effective measurement at low speeds. The invention provides an internal ballistic velocity testing system and method based on magnetic induction intensity.

[0010] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0011] An internal ballistic velocity testing system based on magnetic induction intensity, characterized by:

[0012] It includes an internal ballistic velocity generation system, a signal measurement and acquisition system, and a data analysis, processing, and velocity calculation module;

[0013] The internal ballistic velocity generation system includes a loading system and a magnetic launcher;

[0014] The loading system includes a power chamber and a launch tube connected sequentially from back to front; the power chamber is used to store high-pressure gas for launching; a valve is provided at the connection between the power chamber and the launch tube, through which the power chamber and the inner cavity of the launch tube are connected and separated; the magnetic launching element is installed in the inner cavity of the launch tube, and the opening at the front end of the launch tube is the muzzle;

[0015] During launch, the valve is opened, and the high-pressure gas stored in the power chamber flows into the launch tube, pushing the magnetic launcher forward inside the launch tube and launching it. During the forward movement of the magnetic launcher inside the launch tube, the magnetic induction intensity on the outside of the launch tube wall changes.

[0016] The signal measurement and acquisition system includes S sensors for measuring magnetic induction intensity signals, and a data acquisition system; where S is a natural number greater than or equal to 2.

[0017] S sensors are spaced apart along the axial direction of the transmitting tube on the outer wall of the transmitting tube, and their output ends are respectively connected to the input ends of the S acquisition channels of the data acquisition system; the output end of the data acquisition system is connected to the input end of the data analysis and processing and speed calculation module; the data acquisition system is used to continuously acquire the magnetic induction intensity signals measured by the S sensors at their respective locations in real time, and transmit the acquired S magnetic induction intensity signals to the data analysis and processing and speed calculation module.

[0018] The data analysis and processing and velocity calculation module is used to filter and denoise the collected S magnetic induction intensity signals, perform correlation analysis, and calculate the ballistic velocity inside the magnetic launcher.

[0019] Furthermore, the sensor is a fluxgate sensor or a Hall sensor;

[0020] The S sensors are mounted at intervals along the axial direction of the transmitting tube on the outer wall of the transmitting tube.

[0021] Furthermore, the magnetic launcher includes a conventional piston used in a two-stage light gas cannon, and also includes a magnet;

[0022] The conventional piston includes a piston head, a piston middle section, and a piston tail connected sequentially from front to back, and the piston head and piston tail are both connected to the piston middle section by a threaded connection.

[0023] A recess adapted to the magnet is provided on the rear end face of the piston head; the magnet is disposed in the recess, and the magnet is fixed by threading the piston head to the middle section of the piston.

[0024] Further, the data acquisition system uses a data collector of Donghua Company.

[0025] Meanwhile, the present invention also provides a method for measuring the interior ballistic velocity based on magnetic induction intensity, which is characterized in that it includes the following steps:

[0026] Step 1: Build the above-mentioned interior ballistic velocity measurement system based on magnetic induction intensity;

[0027] Step 2: Close the valve provided at the connection between the power chamber and the launch tube in the interior ballistic velocity measurement system based on magnetic induction intensity built in Step 1; then inject high-pressure gas with the pressure required by the design into the power chamber, set the parameters of the data acquisition system, and activate the data acquisition system and the data analysis, processing and velocity calculation module;

[0028] Step 3: Open the valve closed in Step 2. The high-pressure gas stored in the power chamber flows into the launch tube, pushing the magnetic launch piece to move forward in the launch tube and launch it. During the forward movement of the magnetic launch piece in the launch tube, the magnetic induction intensity outside the wall of the launch tube changes;

[0029] Step 4: Use the data acquisition system activated in Step 2 to continuously and real-time collect the magnetic induction intensity signals measured by the S sensors at their respective positions, and transmit the S magnetic induction intensity signals collected to the data analysis, processing and velocity calculation module;

[0030] Step 5: The data analysis, processing and velocity calculation module respectively performs filtering and noise reduction processing on the S magnetic induction intensity signals collected by the data acquisition system in Step 4;

[0031] Step 6: The data analysis, processing and velocity calculation module calculates the correlation coefficient r of each group of signals with two signals as a group for the S magnetic induction intensity signals after filtering and noise reduction processing in Step 5, and compares the obtained correlation coefficient r with the set correlation coefficient threshold r0: If r≥r0, it is determined that the two signals in this group of signals have good consistency, and record these two signals; if r<r0, it is determined that the two signals in this group of signals have poor consistency and are not recorded; when calculating the correlation coefficient r of each group of signals with two signals as a group, the following conditions should be met: Ensure that each of the S magnetic induction intensity signals after filtering and noise reduction processing in Step 5 has at least one corresponding correlation coefficient r;

[0032] Step 7: Based on the signals recorded in Step 6, calculate the interior ballistic velocity of the magnetic launch piece at the positions of the sensors corresponding to the signals recorded in Step 6 according to the relationship between the step change of the magnetic induction intensity signal and the interior ballistic velocity, and complete the test.

[0033] Furthermore, in step 2, the pressure range of the high-pressure gas required by the design is between 1MPa and 10MPa, and its specific value is set according to the launch speed requirement and is an empirical value.

[0034] Furthermore, in step 5, the filtering and noise reduction process specifically involves:

[0035] Step B1: A value is assigned to the standard deviation σ of the Gaussian signal function in the Gaussian smoothing filter; the Gaussian signal function is:

[0036]

[0037] In the formula: G(x) represents the Gaussian signal function; σ represents the filter standard deviation; x represents the acquired magnetic induction intensity signal;

[0038] Step B2: The acquired magnetic induction intensity signal is subjected to Gaussian smoothing filtering using a Gaussian signal function with a given filtering standard deviation σ to remove high-frequency noise from the signal;

[0039] Step B3: In real time, determine whether the magnetic induction intensity signal after Gaussian smoothing filtering in step B2 is a visible curve; if yes, the visible curve is the magnetic induction intensity signal after removing high-frequency noise, and proceed to step B4; if no, give a new value to the filtering standard deviation σ of the Gaussian signal function in the Gaussian smoothing filter, and then return to step B2.

[0040] Step B4: The magnetic induction intensity signal obtained in step B3 after removing high-frequency noise is processed by a Butterworth low-pass filter to remove low-frequency noise from the signal, and the filtered and noise-reduced magnetic induction intensity signal is obtained, thus completing the filtering and noise reduction process.

[0041] Further, in step B4, when performing Butterworth low-pass filter processing, the transfer function of the Butterworth low-pass filter is:

[0042]

[0043] In the formula: H(jw) represents the transfer function of the Butterworth low-pass filter, where jw represents the complex frequency variable; w represents the sampling frequency of the magnetic flux density signal; w c The frequency of the Butterworth low-pass filter is 50Hz; n represents the order of the Butterworth low-pass filter, which is 4.

[0044] Furthermore, in step 6, the correlation coefficient r of each group of signals is calculated using the following formula:

[0045]

[0046] In the formula: r represents the correlation coefficient; m represents the number of signal acquisition points; x i y i Let represent the magnetic induction intensity at the i-th sampling point of each of the two magnetic induction intensity signals in this group of signals, where 1≤i≤m; These represent the average magnetic induction intensity at the corresponding m sampling points on each of the two magnetic induction intensity signals in this set of signals.

[0047] Furthermore, in step 7, when calculating the ballistic velocity within the magnetic launcher at the sensor position corresponding to each signal recorded in step 6, the calculation process for the ballistic velocity within the magnetic launcher at each sensor position is as follows:

[0048] Step C1: Calculate the first-order difference of the corresponding signal recorded in step 6;

[0049] Step C2: Take 0.1 times the maximum value of the first-order difference of the signal calculated in Step C1 as the set abrupt change threshold; then compare the absolute value of the first-order difference of the signal calculated in Step C1 with the set abrupt change threshold: if the absolute value of the first-order difference of the signal is greater than the set abrupt change threshold, it is determined that abrupt change has occurred in the signal at that point, and detection is performed within a set range before and after the abrupt change point on the signal to extract the abrupt change signal. Then, the abrupt change duration of the signal step change and the abrupt change range of the magnetic induction intensity are obtained from the abrupt change signal; if the absolute value of the first-order difference of the signal is less than or equal to the set abrupt change threshold, it is determined that no abrupt change has occurred in the signal at that point, and no detection is performed.

[0050] Step C3: Based on the abrupt change duration of the signal step change and the abrupt change range of the magnetic induction intensity obtained in Step C2, calculate the ballistic velocity within the magnetic launcher at the corresponding sensor location using the following formula:

[0051]

[0052] In the formula: V represents the ballistic velocity inside the magnetic launcher at the corresponding sensor position; k is the proportionality coefficient, which is the calibration value; dt represents the slope of the magnetic flux density signal step, where dB is the absolute value of the difference between the endpoints of the range corresponding to the abrupt change range of the magnetic flux density obtained in step C2, and dt is the duration of the abrupt change obtained in step C2.

[0053] The beneficial effects of this invention are:

[0054] (1) In the internal ballistic velocity testing system and method based on magnetic induction intensity of the present invention, the sensor used is a sensor for measuring magnetic induction intensity signals. The sensor measures the magnetic induction intensity signals at the locations of each sensor during the forward movement of the magnetic launcher inside the launch tube. The installation and use of the sensor are very simple. During installation, there is no need to drill holes in the launch tube; it can be installed by pasting. Therefore, its installation will not affect the overall structural strength and service life of the loading system. It can be installed on the tube wall throughout the entire internal ballistic motion process. In addition, when using the internal ballistic velocity testing system and method based on magnetic induction intensity of the present invention to perform internal ballistic velocity testing, there is no need to place an acceleration sensor on the launcher. Only a magnet needs to be fixed on a traditional piston to form a magnetic launcher. Therefore, compared with the prior art of placing an acceleration sensor on the launcher to obtain the corresponding... The method for measuring internal ballistic velocity significantly reduces testing costs. Furthermore, the sensor in this invention measures magnetic induction intensity signals, rather than the circumferential strain of the launch tube wall as measured in existing strain gauge-based methods. Therefore, its measurement accuracy is unaffected by the flatness of the launch tube surface or the quality of sensor attachment and installation, resulting in a substantial improvement in testing accuracy. Simultaneously, because the sensor measures magnetic induction intensity signals, its measurement is unaffected by the speed of the magnetic launcher, enabling effective measurement even during low-speed movement. In summary, this invention solves the technical problems of existing internal ballistic velocity testing methods, such as complex installation and use of the testing system, installation affecting the overall structural strength and lifespan of the loading system, high testing costs, low testing accuracy, and inability to achieve effective measurement during low-speed movement.

[0055] (2) In the internal ballistic velocity testing system and method based on magnetic induction intensity of the present invention, the principle of magnetic induction intensity signal testing is applied to the internal ballistic velocity testing. Preferably, the sensor is set at intervals along the axial direction of the launch tube on the outer wall of the launch tube by pasting. Preferably, the magnetic launching element that can cause the magnetic induction intensity on the outer wall of the launch tube to change is obtained by setting a pit adapted to the magnet on the rear end face of the piston head of the traditional piston and making a local improvement design on the traditional piston structure, so as to provide motion characteristics for the sensor to measure the magnetic induction intensity signal. When installing the sensor, there is no need to drill holes in the launch tube. When obtaining the magnetic launching element, the structure of the traditional piston is not damaged. Therefore, it reduces the dependence on the conditions of the loading system itself, reduces the prerequisites for internal ballistic velocity testing, reduces the condition restrictions of internal ballistic velocity testing, improves the simplicity and effectiveness of internal ballistic velocity testing throughout the entire process, and can achieve non-destructive testing. It can meet the needs of internal ballistic velocity testing of the loading system after finalization, and can be applied to internal ballistic velocity testing of various loading methods. It can guide the design of internal ballistic structure parameters and launch parameters of the loading system and improve the accuracy of internal ballistic velocity calculation.

[0056] (3) In the internal ballistic velocity testing system and method based on magnetic induction intensity of the present invention, when calculating the internal ballistic velocity, the collected magnetic induction intensity signal is first filtered and denoised, and correlation analysis is performed to remove high-frequency noise and low-frequency noise in the signal, and a useful signal with good consistency is selected from it; then, using the useful signal with good consistency, the internal ballistic velocity of the magnetic launcher at the sensor position corresponding to each useful signal with good consistency is calculated based on the relationship between the step change of the magnetic induction intensity signal and the internal ballistic velocity; since the high-frequency noise and low-frequency noise in the signal are removed and correlation analysis is performed before the calculation, the internal ballistic velocity calculated by it has high accuracy. When the high-precision internal ballistic velocity is used to optimize the loading system structural parameters and launch parameters, and to verify the effectiveness of the internal ballistic calculation model, the optimization and verification results are also more accurate, thereby improving the accuracy of the launch velocity calculation results.

[0057] (4) In the internal ballistic velocity testing system and method based on magnetic induction intensity of the present invention, the internal ballistic velocity testing system is built from the perspective of magnetic induction intensity signal measurement. Based on the relationship between the step change of magnetic induction intensity signal and internal ballistic velocity, the internal ballistic velocity is obtained, which increases the diversity of internal ballistic velocity testing. Attached Figure Description

[0058] Figure 1 This is a schematic diagram of the internal ballistic velocity generation system in an embodiment of the internal ballistic velocity testing system based on magnetic induction intensity of the present invention.

[0059] Figure 2 This is a schematic diagram of the structure of the internal ballistic velocity testing system based on magnetic induction intensity of the present invention, in which the sensors are spaced apart along the axial direction of the launch tube on the outer wall of the launch tube.

[0060] Figure 3 In step 4 of the embodiment of the internal ballistic velocity testing method based on magnetic induction intensity of the present invention, the data acquisition system acquires the magnetic induction intensity signal measured by sensor number one and the magnetic induction intensity signal measured by sensor number six; wherein:

[0061] (a) is the magnetic induction intensity signal measured by the No. 1 sensor acquired by the data acquisition system;

[0062] (b) is the magnetic induction intensity signal measured by sensor number six, which was acquired by the data acquisition system;

[0063] Figure 4In step 5 of the embodiment of the internal ballistic velocity testing method based on magnetic induction intensity of the present invention, the data analysis and velocity calculation module performs filtering and noise reduction processing on the magnetic induction intensity signals measured by sensor 1 and sensor 6 acquired by the data acquisition system, respectively, to obtain the corresponding signals; wherein:

[0064] (c) is the signal obtained after filtering and noise reduction processing of the magnetic induction intensity signal measured by the No. 1 sensor acquired by the data acquisition system;

[0065] (d) is the signal obtained after filtering and noise reduction of the magnetic induction intensity signal measured by sensor No. 6 acquired by the data acquisition system;

[0066] Figure 5 In step C2 of step 7 of the embodiment of the internal ballistic velocity testing method based on magnetic induction intensity of the present invention, the data analysis and velocity calculation module extracts abrupt change signals from the magnetic induction intensity signals measured by sensor 1 and sensor 6 after filtering and noise reduction processing; wherein:

[0067] (e) is the abrupt signal extracted from the magnetic induction intensity signal measured by the No. 1 sensor after recording and filtering and noise reduction.

[0068] (f) is the abrupt change signal extracted from the magnetic induction intensity signal measured by sensor No. 6 after filtering and noise reduction processing.

[0069] The labels in the diagram are explained as follows:

[0070] 1-Power chamber, 2-Launch tube, 3-Valve, 4-Magnetic launcher, 51-Sensor No. 1, 52-Sensor No. 2, 53-Sensor No. 3, 54-Sensor No. 4, 55-Sensor No. 5, 56-Sensor No. 6. Detailed Implementation

[0071] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0072] The present invention discloses an internal ballistic velocity testing system based on magnetic induction intensity, comprising an internal ballistic velocity generation system, a signal measurement and acquisition system, and a data analysis and processing and velocity calculation module.

[0073] See Figure 1The aforementioned internal ballistic velocity generation system includes a loading system and a magnetic launcher 4. The loading system includes a power chamber 1 and a launch tube 2 connected sequentially from back to front. The power chamber 1 is used to store high-pressure gas for launch. A valve 3 is provided at the connection between the power chamber 1 and the launch tube 2, through which the internal cavities of the power chamber 1 and the launch tube 2 are connected and separated. The magnetic launcher 4 is installed in the internal cavity of the launch tube 2, and the opening at the front end of the launch tube 2 is the muzzle. In this embodiment, the magnetic launcher 4 is preferably modified from a traditional piston used in a two-stage light gas gun. It includes a traditional piston used in a two-stage light gas gun and a magnet. The traditional piston used in a two-stage light gas gun includes a piston head, a piston middle section, and a piston tail connected sequentially from front to back, and the piston head and piston tail are both connected to the piston middle section by a threaded connection. In this embodiment, when fixing the magnet to the traditional piston, only a recess adapted to the magnet is provided on the rear end face of the piston head of the traditional piston. The magnet is placed in the recess, and the magnet is fixed by threading the piston head to the piston middle section. During launch, valve 3 is opened, and the high-pressure gas stored in power chamber 1 flows into launch tube 2, which pushes the magnetic launcher 4 forward in launch tube 2 and launches it. During the forward movement of the magnetic launcher 4 in launch tube 2, the magnetic induction intensity on the outside of the tube wall of launch tube 2 changes.

[0074] The aforementioned signal measurement and acquisition system includes S sensors for measuring magnetic flux density signals, and a data acquisition system; S is a natural number greater than or equal to 2; see [link to documentation]. Figure 2S sensors are spaced apart along the axial direction of the transmitting tube 2 on the outer wall of the transmitting tube 2, and their output terminals are connected one-to-one with the input terminals of the S acquisition channels of the data acquisition system. In this embodiment, S equals 6, that is, 6 sensors are spaced apart along the axial direction of the transmitting tube 2 on the outer wall of the transmitting tube 2. The 6 sensors, from back to front, are sensor 1 51, sensor 2 52, sensor 3 53, sensor 4 54, sensor 55, and sensor 6 56. In this embodiment, all 6 sensors are fluxgate sensors, and the 6 fluxgate sensors are spaced apart along the axial direction of the transmitting tube 2 by adhesive bonding. In addition to the fluxgate sensors used in this embodiment, other sensors capable of measuring magnetic induction intensity signals, such as Hall sensors, can also be used. When installing the sensors, in addition to the adhesive bonding method used in this embodiment, other installation methods that will not damage the original structure of the transmitting tube 2 can also be used. In this embodiment, the data acquisition system uses a data acquisition instrument from Donghua Company. The output of the data acquisition system is connected to the input of the data analysis, processing and speed calculation module, which in this embodiment is connected to a computer. The data acquisition system is used to continuously acquire the magnetic induction intensity signals measured by the S sensors at their respective locations in real time, and transmit the acquired S magnetic induction intensity signals to the data analysis, processing and speed calculation module.

[0075] The aforementioned data analysis, processing, and velocity calculation module is used to sequentially filter and denoise the collected S magnetic induction intensity signals, perform correlation analysis, and calculate the ballistic velocity within the magnetic launcher 4. In this embodiment, the aforementioned data analysis, processing, and velocity calculation module includes a memory and a processor. The memory stores a computer program, and when the computer program is executed by the processor, it performs the following process:

[0076] Step A1: Receive the S magnetic induction intensity signals acquired by the data acquisition system, and perform filtering and noise reduction processing on the S magnetic induction intensity signals respectively; in this embodiment, the filtering and noise reduction processing is performed on the 6 magnetic induction intensity signals respectively.

[0077] Step A2: For the S magnetic induction intensity signals after filtering and noise reduction in Step A1, taking two signals as a group, calculate the correlation coefficient r of each group of signals respectively, and compare the obtained correlation coefficient r with the set correlation coefficient threshold r0: If r ≥ r0, it is determined that the two signals in this group of signals have good consistency, and record these two signals; if r < r0, it is determined that the two signals in this group of signals have poor consistency and are not recorded; when taking two signals as a group and calculating the correlation coefficient r of each group of signals respectively, the following conditions should be met: Ensure that each of the S magnetic induction intensity signals after filtering and noise reduction in Step A1 has at least one corresponding correlation coefficient r; in this embodiment, when taking two signals as a group and calculating the correlation coefficient r of each group of signals respectively, it should be ensured that each of the 6 magnetic induction intensity signals after filtering and noise reduction has at least one corresponding correlation coefficient r;

[0078] Step A3: Based on the signals recorded in Step A2, and based on the relationship between the step change of the magnetic induction intensity signal and the interior ballistic velocity, calculate the interior ballistic velocity of the magnetic emitter 4 at the sensor position corresponding to each signal recorded in Step A2, and complete the test.

[0079] In addition, the present invention also provides an interior ballistic velocity test method based on magnetic induction intensity, including the following steps:

[0080] Step 1: Build the above-mentioned interior ballistic velocity test system based on magnetic induction intensity;

[0081] During setup, the volume of the power chamber 1 is typically less than 1L, and the weight of the magnetic emitter 4 is typically between 1g and 10g. The connecting bolts between the power chamber 1 and the emitter tube 2 are released, the contact surface between them is loosened, and the magnetic emitter 4 is placed at the opening of the rear end of the emitter tube 2. Then, the chambers are closed, i.e., the power chamber 1 and the emitter tube 2 are tightly connected using bolts. In this embodiment, the volume of the power chamber 1 is 0.3L; the length of the emitter tube 2 is 1.8m, and its diameter is 10mm; the diameter of the magnetic emitter 4 is 10mm, and its weight is 2g. When sensors are installed along the axial direction on the outer wall of the emitter tube 2, the number of sensors is determined by the length of the emitter tube 2, and adjacent sensors are typically spaced apart. The distance is 0.2m to 1m, but if the ballistic velocity within a section of the launch tube 2 is not of concern, sensors may not be installed in that section. In this embodiment, six fluxgate sensors are installed along the axial direction on the outer wall of the launch tube 2. The center distance between sensor 1 51 and sensor 2 52 is 29.5cm, the center distance between sensor 2 52 and sensor 3 53 is 36.5cm, the center distance between sensor 3 53 and sensor 4 54 is 32.5cm, the center distance between sensor 4 54 and sensor 55 is 24.5cm, and the center distance between sensor 55 and sensor 6 56 is 34.5cm. The data acquisition system uses a data acquisition instrument from Donghua Company.

[0082] Step 2: Close valve 3 at the connection between power chamber 1 and launch tube 2 in the internal ballistic velocity test system based on magnetic induction intensity built in Step 1; then inject high-pressure gas at the design required pressure into power chamber 1, set the parameters of the data acquisition system, and turn on the data acquisition system and the data analysis and processing and velocity calculation module.

[0083] When injecting high-pressure gas at the designed pressure into the power chamber 1, the pressure range of the high-pressure gas is usually between 1 MPa and 10 MPa, and its specific value is set according to the launch speed requirements and is an empirical value; in this embodiment, the pressure of the high-pressure gas injected into the power chamber 1 is 4.7 MPa; when setting the parameters of the data acquisition system, the sampling frequency of the data acquisition system is usually set between 100 kHz and 50 MHz, and its specific setting value is set according to the estimated internal ballistic velocity; in this embodiment, the sampling frequency of the data acquisition system is set to 100 kHz;

[0084] Step 3: Open valve 3, which was closed in step 2. The high-pressure gas stored in power chamber 1 flows into the launching tube 2, which pushes the magnetic launching element 4 to move forward in the launching tube 2 and launch it. During the forward movement of the magnetic launching element 4 in the launching tube 2, the magnetic induction intensity on the outside of the tube wall of the launching tube 2 changes.

[0085] Step 4: The data acquisition system activated in Step 2 is used to continuously acquire the magnetic induction intensity signals measured by the S sensors at their respective locations in real time, and the acquired S magnetic induction intensity signals are transmitted to the data analysis and processing and speed calculation module.

[0086] In this embodiment, the data acquisition system acquires six magnetic induction intensity signals. Taking sensor 1 (51) and sensor 6 (56) as examples, the magnetic induction intensity signals measured by sensor 1 (51) and sensor 6 (56) acquired by the data acquisition system in this embodiment are as follows: Figure 3 As shown in (a) and (b);

[0087] Step 5: The data analysis, processing, and speed calculation module performs filtering and noise reduction on the S magnetic induction intensity signals acquired by the data acquisition system in Step 4; that is, it performs the following processes on the S acquired magnetic induction intensity signals respectively:

[0088] Step B1: A value is given for the standard deviation σ of the Gaussian signal function in the Gaussian smoothing filter; the Gaussian signal function is:

[0089]

[0090] In the formula: G(x) represents the Gaussian signal function; σ represents the filter standard deviation; x represents the acquired magnetic induction intensity signal;

[0091] Step B2: The acquired magnetic induction intensity signal is subjected to Gaussian smoothing filtering using a Gaussian signal function with a given filtering standard deviation σ to remove high-frequency noise from the signal while preserving the signal's trend and variation.

[0092] Step B3: In real time, determine whether the magnetic field strength signal after Gaussian smoothing filtering in step B2 is a visible curve; if so, the visible curve is the magnetic field strength signal after removing high-frequency noise, and proceed to step B4; if not, give a new value to the filtering standard deviation σ of the Gaussian signal function in the above Gaussian smoothing filtering, and then return to step B2.

[0093] In this embodiment, when the given standard deviation of the filter σ is 5, the magnetic induction intensity signal after Gaussian smoothing filtering becomes a visible curve, and the Gaussian smoothing filtering of the signal is completed.

[0094] Step B4: The magnetic induction intensity signal obtained in step B3 after removing high-frequency noise is processed by a Butterworth low-pass filter to remove low-frequency noise from the signal, and the magnetic induction intensity signal after filtering and noise reduction is obtained, thus completing the filtering and noise reduction process.

[0095] When performing Butterworth low-pass filter processing as described above, the transfer function of the Butterworth low-pass filter is as follows:

[0096]

[0097] In the formula: H(jw) represents the transfer function of the Butterworth low-pass filter, where jw represents the complex frequency variable; w represents the sampling frequency of the magnetic induction intensity signal; w c represents the frequency of the Butterworth low-pass filter; since the frequencies of environmental noise and electromagnetic interference signals are generally above 50 Hz, the frequency w c of the Butterworth low-pass filter is usually taken as 50 Hz; n represents the order of the Butterworth low-pass filter; in order to make the signal steeper, the order n of the Butterworth low-pass filter is usually taken as 4, which can ensure that important low-frequency information in the signal is retained; in order to avoid phase distortion and maintain temporal alignment, preferably, zero-phase filtering is used for Butterworth low-pass filter processing, which can ensure that the temporal characteristics of the signal remain unchanged;

[0098] Taking the first sensor 51 and the sixth sensor 56 as an example, in this embodiment, after the data analysis and processing and speed calculation module filters and denoises the magnetic induction intensity signals measured by the first sensor 51 and the sixth sensor 56 collected by the data acquisition system respectively, the corresponding signals obtained are respectively as Figure 4 shown in (c) and (d) below;

[0099] Step 6: The data analysis and processing and speed calculation module takes two signals as a group from the S magnetic induction intensity signals after filtering and denoising in Step 5, calculates the correlation coefficient r of each group of signals respectively, and compares the obtained correlation coefficient r with the set correlation coefficient threshold r0: If r ≥ r0, it is determined that the two signals in this group of signals are in good agreement, and these two signals are recorded; if r < r0, it is determined that the two signals in this group of signals are in poor agreement and are not recorded; when calculating the correlation coefficient r of each group of signals with two signals as a group, the following conditions should be met: Each of the S magnetic induction intensity signals after filtering and denoising in Step 5 should have at least one corresponding correlation coefficient r;

[0100] In this embodiment, when calculating the correlation coefficient r of each group of signals with two signals as a group, each of the 6 magnetic induction intensity signals after filtering and denoising should have at least one corresponding correlation coefficient r; when calculating the correlation coefficient r of each group of signals as described above, the following formula is used for calculation:

[0101]

[0102] In the formula: r represents the correlation coefficient; m represents the number of signal acquisition points; x iy i Let represent the magnetic induction intensity at the i-th sampling point of each of the two magnetic induction intensity signals in this group of signals, where 1≤i≤m; These represent the average magnetic flux density at the m sampling points corresponding to the two magnetic flux density signals in this set of signals, respectively.

[0103] By calculating the correlation coefficient r between signals from different sensors and conducting correlation analysis, the time delay relationship between signals from different sensors can be clarified, and the synchronization relationship between signals can be determined. When the correlation coefficient r is 1, it indicates that the two signals are completely linearly positively correlated; when the correlation coefficient r is 0, it indicates that the two signals are uncorrelated; when the correlation coefficient r is -1, it indicates that the two signals are completely linearly negatively correlated. The correlation coefficient threshold r0 set above is usually taken as 0.8. In this embodiment, taking the signals corresponding to sensor 1 51 and sensor 6 56 as an example, the correlation coefficient r calculated using the signals corresponding to sensor 1 51 and sensor 6 56 is 0.98, which is greater than the set correlation coefficient threshold r0 of 0.8. This indicates that the signals corresponding to sensor 1 51 and sensor 6 56 have good consistency and are useful signals. They are recorded and subsequently used for calculating the ballistic velocity inside the magnetic launcher 4 at the corresponding sensor position.

[0104] Step 7: Based on the signals recorded in Step 6, and the relationship between the step change of the magnetic induction intensity signal and the internal ballistic velocity, calculate the internal ballistic velocity of the magnetic launcher 4 at the sensor position corresponding to each signal recorded in Step 6.

[0105] When calculating the ballistic velocity within the magnetic launcher 4 at the sensor positions corresponding to each signal recorded in step 6, the calculation process for the ballistic velocity within the magnetic launcher 4 at each sensor position is as follows:

[0106] Step C1: Calculate the first-order difference of the corresponding signal recorded in step 6;

[0107] To facilitate the detection of signal abrupt changes, which are usually manifested as drastic changes in signal value within a short period of time, these changes can be detected by calculating the first-order difference of the signal.

[0108] Step C2: Take 0.1 times the maximum value of the first-order difference of the signal calculated in Step C1 as the set abrupt change threshold; then compare the absolute value of the first-order difference of the signal calculated in Step C1 with the set abrupt change threshold: if the absolute value of the first-order difference of the signal is greater than the set abrupt change threshold, it is determined that abrupt change has occurred in the signal at that point, and detection is performed within a set range before and after the abrupt change point on the signal to extract the abrupt change signal. Then, the abrupt change duration of the signal step change and the abrupt change range of the magnetic induction intensity are obtained from the abrupt change signal; if the absolute value of the first-order difference of the signal is less than or equal to the set abrupt change threshold, it is determined that no abrupt change has occurred in the signal at that point, and no detection is performed.

[0109] In this embodiment, taking sensor 51 (number 1) and sensor 56 (number 6) as examples, the data analysis, processing, and speed calculation module extracts abrupt change signals from the magnetic induction intensity signals measured by sensor 51 and sensor 56 after filtering and noise reduction processing, respectively. Figure 5 As shown in (e) and (f) in the figure; the abrupt change duration of the signal step change obtained from the abrupt signal corresponding to sensor 51 is 0.301s, the abrupt change range of magnetic induction intensity is 24602nT~22123nT, and the absolute value of the difference between the endpoints of the range is 2.479uT; the abrupt change duration of the signal step change obtained from the abrupt signal corresponding to sensor 56 is 0.035s, the abrupt change range of magnetic induction intensity is 24314nT~22685nT, and the absolute value of the difference between the endpoints of the range is 1.629uT;

[0110] Step C3: Based on the abrupt change duration of the signal step change and the abrupt change range of the magnetic induction intensity obtained in step C2, calculate the ballistic velocity of the magnetic launcher 4 at the corresponding sensor position.

[0111] The sensor detects the distance range of the magnetic launcher 4 within an "unknown" length Δx. By detecting and extracting the abrupt signal, the slope of the signal step can be obtained. Assuming Δx is sufficiently small, the magnetic induction intensity B is proportional to the position x of the magnetic launcher 4, i.e., dx = kdB. Then, the ballistic velocity within the magnetic launcher 4 at the corresponding sensor position is calculated using the following formula:

[0112]

[0113] In the formula: V represents the ballistic velocity inside the magnetic launcher 4 at the corresponding sensor position; k is the proportionality coefficient, which is the calibration value. Under the same working condition, the magnetic launcher 4 has the same proportionality coefficient k at different sensor positions. dt represents the slope of the magnetic flux density signal step, where dB is the absolute value of the difference between the endpoints of the range corresponding to the abrupt change range of the magnetic flux density obtained in step C2, and dt is the abrupt change duration obtained in step C2.

[0114] In this embodiment, sensor 51 and sensor 56 correspond to... The values ​​are 8.23 ​​uT / s and 46.5 uT / s respectively; k is taken as 10.15 m / uT. The calculated ballistic velocity inside the magnetic launcher 4 at the position of sensor 1 51 is 83.53 m / s, and the calculated ballistic velocity inside the magnetic launcher 4 at the position of sensor 6 56 is 472 m / s.

[0115] The internal ballistic velocity testing system and method based on magnetic induction intensity of this invention can be used to test the internal ballistic velocity. After obtaining the internal ballistic velocity, it can be compared and analyzed with the theoretical calculation results. This can be used to optimize the system structural parameters and launch parameters, verify the effectiveness of the internal ballistic calculation model, and thus improve the accuracy of the launch velocity calculation results.

[0116] In summary, this invention establishes an internal ballistic velocity testing system from the perspective of magnetic induction intensity signal measurement. Based on the relationship between the step change of magnetic induction intensity signal and internal ballistic velocity, the internal ballistic velocity is obtained, increasing the diversity of internal ballistic velocity testing.

Claims

1. An internal ballistic velocity testing system based on magnetic induction intensity, characterized in that: It includes an internal ballistic velocity generation system, a signal measurement and acquisition system, and a data analysis, processing, and velocity calculation module; The internal ballistic velocity generation system includes a loading system and a magnetic launcher (4); The loading system includes a power chamber (1) and a launch tube (2) connected sequentially from back to front; the power chamber (1) is used to store high-pressure gas for launching; a valve (3) is provided at the connection between the power chamber (1) and the launch tube (2), through which the power chamber (1) and the inner cavity of the launch tube (2) are connected and separated; the magnetic launching element (4) is installed in the inner cavity of the launch tube (2), and the opening at the front end of the launch tube (2) is the muzzle; When launching, the valve (3) is opened, and the high-pressure gas stored in the power chamber (1) flows into the launch tube (2), which pushes the magnetic launcher (4) to move forward in the launch tube (2) and launch it. During the forward movement of the magnetic launcher (4) in the launch tube (2), the magnetic induction intensity on the outside of the tube wall of the launch tube (2) changes. The signal measurement and acquisition system includes S sensors for measuring magnetic induction intensity signals, and a data acquisition system; where S is a natural number greater than or equal to 2. S sensors are spaced apart along the axial direction of the transmitting tube (2) on the outer wall of the transmitting tube (2), and their output ends are respectively connected to the input ends of the S acquisition channels of the data acquisition system; the output end of the data acquisition system is connected to the input end of the data analysis and processing and speed calculation module; the data acquisition system is used to continuously acquire the magnetic induction intensity signals measured by the S sensors at their respective locations in real time, and transmit the acquired S magnetic induction intensity signals to the data analysis and processing and speed calculation module; The data analysis and processing and velocity calculation module is used to filter and denoise the collected S magnetic induction intensity signals, perform correlation analysis, and calculate the ballistic velocity inside the magnetic launcher (4).

2. The internal ballistic velocity testing system based on magnetic induction intensity according to claim 1, characterized in that: The sensor is either a fluxgate sensor or a Hall sensor; S sensors are arranged at intervals along the axial direction of the transmitting tube (2) on the outer wall of the transmitting tube (2) by adhesive bonding.

3. The internal ballistic velocity testing system based on magnetic induction intensity according to claim 1, characterized in that: The magnetic launcher (4) includes a conventional piston used in a secondary light gas gun, and also includes a magnet; The conventional piston includes a piston head, a piston middle section, and a piston tail connected sequentially from front to back, and the piston head and piston tail are both connected to the piston middle section by a threaded connection. A recess adapted to the magnet is provided on the rear end face of the piston head; the magnet is disposed in the recess, and the magnet is fixed by threading the piston head to the middle section of the piston.

4. The internal ballistic velocity testing system based on magnetic induction intensity according to claim 1, characterized in that: The data acquisition system uses a data collector from Donghua Company.

5. A method for testing internal ballistic velocity based on magnetic induction intensity, characterized in that, It includes the following steps: Step 1: Set up the internal ballistic velocity test system based on magnetic induction intensity as described in any one of Claims 1 to 4. Step 2: Close the valve (3) provided at the connection of the power chamber (1) and the launch tube (2) in the internal ballistic velocity test system based on magnetic induction intensity set up in Step 1; then inject high-pressure gas with a pressure within the design requirements into the power chamber (1), set the parameters of the data acquisition system, and turn on the data acquisition system and the data analysis, processing, and velocity calculation module. Step 3: Open the valve (3) closed in Step 2. The high-pressure gas stored in the power chamber (1) flows into the launch tube (2), pushing the magnetic launch piece (4) to move forward in the launch tube (2) and launch it. During the forward movement of the magnetic launch piece (4) in the launch tube (2), the magnetic induction intensity outside the wall of the launch tube (2) changes. Step 4: Use the data acquisition system turned on in Step 2 to continuously and real-time collect the magnetic induction intensity signals measured by the S sensors at their respective positions, and transmit the S collected magnetic induction intensity signals to the data analysis, processing, and velocity calculation module. Step 5: The data analysis, processing, and velocity calculation module respectively performs filtering and noise reduction processing on the S magnetic induction intensity signals collected by the data acquisition system in Step 4. Step 6: The data analysis, processing, and velocity calculation module calculates the correlation coefficient r for each group of two signals among the S magnetic induction intensity signals after filtering and noise reduction processing in Step 5, and compares the obtained correlation coefficient r with the set correlation coefficient threshold r0: If r≥r0, it is determined that the two signals in this group have good consistency, and record these two signals; if r<r0, it is determined that the two signals in this group have poor consistency and are not recorded; when calculating the correlation coefficient r for each group of two signals, the following conditions should be met: Ensure that each of the S magnetic induction intensity signals after filtering and noise reduction processing in Step 5 has at least one corresponding correlation coefficient r. Step 7: Based on the signals recorded in Step 6, calculate the internal ballistic velocity of the magnetic launch piece (4) at the positions of the sensors corresponding to the signals recorded in Step 6 according to the relationship between the step change of the magnetic induction intensity signal and the internal ballistic velocity, and complete the test.

6. The internal ballistic velocity test method based on magnetic induction intensity according to Claim 5, wherein: In Step 2, the pressure range of the high-pressure gas with the design requirements is between 1 MPa and 10 MPa, and its specific value is set according to the launch velocity requirement, which is an empirical value.

7. The internal ballistic velocity test method based on magnetic induction intensity according to Claim 5, wherein: In Step 5, the specific filtering and noise reduction processing is as follows: Step B1: Give a value to the filtering standard deviation σ of the Gaussian signal function in Gaussian smoothing filtering; the Gaussian signal function is: In the formula: G(x) represents the Gaussian signal function; σ represents the filter standard deviation; x represents the acquired magnetic induction intensity signal; Step B2: The acquired magnetic induction intensity signal is subjected to Gaussian smoothing filtering using a Gaussian signal function with a given filtering standard deviation σ to remove high-frequency noise from the signal; Step B3: In real time, determine whether the magnetic induction intensity signal after Gaussian smoothing filtering in step B2 is a visible curve; if yes, the visible curve is the magnetic induction intensity signal after removing high-frequency noise, and proceed to step B4; if no, give a new value to the filtering standard deviation σ of the Gaussian signal function in the Gaussian smoothing filter, and then return to step B2. Step B4: The magnetic induction intensity signal obtained in step B3 after removing high-frequency noise is processed by a Butterworth low-pass filter to remove low-frequency noise from the signal, and the filtered and noise-reduced magnetic induction intensity signal is obtained, thus completing the filtering and noise reduction process.

8. The method for testing internal ballistic velocity based on magnetic induction intensity according to claim 7, characterized in that: In step B4, when performing Butterworth low-pass filter processing, the transfer function of the Butterworth low-pass filter is: In the formula: H(jw) represents the transfer function of the Butterworth low-pass filter, where jw represents the complex frequency variable; w represents the sampling frequency of the magnetic flux density signal; w c The frequency of the Butterworth low-pass filter is 50Hz; n represents the order of the Butterworth low-pass filter, which is 4.

9. The method for testing internal ballistic velocity based on magnetic induction intensity according to claim 5, characterized in that: In step 6, the correlation coefficient r of each group of signals is calculated using the following formula: In the formula: r represents the correlation coefficient; m represents the number of signal acquisition points; x i y i Let represent the magnetic induction intensity at the i-th sampling point of each of the two magnetic induction intensity signals in this group of signals, where 1≤i≤m; These represent the average magnetic induction intensity at the corresponding m sampling points on each of the two magnetic induction intensity signals in this set of signals.

10. The method for testing internal ballistic velocity based on magnetic induction intensity according to claim 5, characterized in that: In step 7, when calculating the ballistic velocity inside the magnetic launcher (4) at the sensor position corresponding to each signal recorded in step 6, the calculation process for the ballistic velocity inside the magnetic launcher (4) at each sensor position is as follows: Step C1: Calculate the first-order difference of the corresponding signal recorded in step 6; Step C2: Take 0.1 times the maximum value of the first-order difference of the signal calculated in Step C1 as the set abrupt change threshold; then compare the absolute value of the first-order difference of the signal calculated in Step C1 with the set abrupt change threshold: if the absolute value of the first-order difference of the signal is greater than the set abrupt change threshold, it is determined that abrupt change has occurred in the signal at that point, and detection is performed within a set range before and after the abrupt change point on the signal to extract the abrupt change signal. Then, the abrupt change duration of the signal step change and the abrupt change range of the magnetic induction intensity are obtained from the abrupt change signal; if the absolute value of the first-order difference of the signal is less than or equal to the set abrupt change threshold, it is determined that no abrupt change has occurred in the signal at that point, and no detection is performed. Step C3: Based on the abrupt change duration of the signal step change and the abrupt change range of the magnetic induction intensity obtained in step C2, calculate the ballistic velocity inside the magnetic launcher (4) at the corresponding sensor location using the following formula: In the formula: V represents the ballistic velocity inside the magnetic launcher (4) at the corresponding sensor position; k is the proportionality coefficient, which is the calibration value; dt represents the slope of the magnetic flux density signal step, where dB is the absolute value of the difference between the endpoints of the range corresponding to the abrupt change range of the magnetic flux density obtained in step C2, and dt is the duration of the abrupt change obtained in step C2.

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