Light gas gun barrel vacuum pumping assembly with electromagnetic induction velocity measurement function and application method

Abstract

The application discloses a light gas gun barrel vacuum pumping assembly with an electromagnetic induction speed measuring function and an application method, which comprises an electromagnetic induction speed measuring device for measuring the speed of a ferromagnetic projectile and having an internal cavity for the passage of the projectile; and a barrel vacuum pumping assembly comprising a base provided with a first interface for coaxial sealing connection with a light gas gun barrel and a second interface in air path communication with the internal cavity, and at least one third interface for connection with a vacuum pumping device; when the vacuum pumping device is in operation, the light gas gun barrel, the barrel vacuum pumping assembly and the internal cavity of the electromagnetic induction speed measuring device form a sealed air path which can be pumped as a whole. Before launching, the generation of muzzle turbulence is completely avoided, and the stability of the posture of the projectile is ensured. Meanwhile, the vacuum pumping also reduces the aerodynamic resistance of the projectile in the barrel, which is favorable for improving the muzzle velocity and the consistency of the speed.

Description

Technical Field

[0001] This invention relates to the field of ballistic testing technology and light gas gun experimental equipment, and in particular to a vacuum pumping assembly for a light gas gun barrel with electromagnetic induction velocity measurement function and its application method. Background Technology

[0002] Light gas guns are a type of experimental equipment widely used in high-speed ballistic testing, materials impact response, and high-pressure physics research. To accurately obtain the velocity parameters of a projectile during its exit from the barrel or during flight, current methods mainly include high-speed imaging, laser velocimetry, and electrical probe methods (such as the broken wire method and the continuity / discontinuity target method). Among these, high-speed imaging is complex, expensive, and requires extremely precise site and calibration conditions; while laser velocimetry has the advantage of being non-contact, it is easily triggered by propellant residue, microparticles, or smoke in the harsh muzzle environment, leading to measurement failure; and electrical probe methods typically require physical contact or blockage with the projectile, which may alter the projectile's flight attitude and surface morphology, and its trigger signal is easily interfered with by the high-speed airflow at the muzzle.

[0003] Electromagnetic induction velocity measurement, based on Faraday's law of electromagnetic induction, enables non-contact measurement of ferromagnetic projectiles. It boasts significant advantages such as low cost, compact structure, and sensitivity only to ferromagnetic materials, naturally resisting interference from microparticles, making it a preferred solution for ferromagnetic projectile velocity measurement. However, the inventors have discovered a fatal flaw when applying existing electromagnetic induction velocity measurement devices directly to conventional light gas guns lacking vacuum capabilities: when the projectile is propelled from the barrel by high-pressure gas, the projectile pushes the gas in front of it out of the barrel. This high-speed airflow, upon entering the velocity measurement device, interacts violently with the device's outer shell, support, coils, and other internal structures, forming extremely complex muzzle turbulence, including eddies and reflected waves. This turbulence exerts an uncontrollable aerodynamic torque on the projectile, which has just left the barrel and whose flight attitude is still unstable, severely interfering with the projectile's exit attitude stability and even causing it to tumble or yaw significantly, seriously affecting the accuracy and reliability of subsequent impact experiments. Especially when using low-density, easily diffusible gases such as helium as the driving medium, the residual air in the barrel and the driving gas are not stratified or mixed evenly, which will form gas clouds with extremely uneven density. After these gas clouds are ejected in sequence, they will induce more serious complex vortex structures in the velocity measurement area, further amplifying the interference effect on the projectile attitude.

[0004] Therefore, how to develop a device and method that can effectively suppress or even eliminate turbulence inside the muzzle and velocity measuring device, thereby significantly improving the stability of the projectile's exit attitude, without sacrificing the original advantages of electromagnetic induction velocity measurement such as non-contact and low cost, has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] This invention aims to propose a vacuum pumping assembly for a light gas gun barrel with electromagnetic induction velocity measurement function and its application method, in order to solve the problem that when electromagnetic induction velocity measurement devices are used in vacuum-less light gas guns, the turbulence caused by premature air jet from the muzzle leads to poor stability of the projectile's exit attitude.

[0006] This invention proposes a vacuum assembly for a light gas cannon barrel with electromagnetic induction velocity measurement function, comprising: an electromagnetic induction velocity measuring device for measuring the velocity of a ferromagnetic projectile, having an internal cavity through which the projectile passes; and a barrel vacuum assembly, including a base having a first interface for coaxial and sealed connection with the light gas cannon barrel and a second interface communicating with the air passage of the internal cavity, and the base also having at least one third interface for connecting a vacuum pumping device; when the vacuum pumping device is working, the light gas cannon barrel, the barrel vacuum assembly, and the internal cavity of the electromagnetic induction velocity measuring device form a sealed air passage that can be evacuated as a whole.

[0007] Furthermore, the electromagnetic induction velocity measuring device includes a housing and at least two electromagnetic induction velocity measuring modules that are sequentially fixed inside the housing along the projectile's flight direction, for generating a time difference signal characterizing the projectile's passage through two adjacent velocity measuring modules.

[0008] Furthermore, the electromagnetic induction speed measuring module includes: a permanent magnet ring for providing a static bias magnetic field; two magnetic guide rings respectively disposed on both axial sides of the permanent magnet ring for converging the magnetic field; and an insulated coil support disposed between the two magnetic guide rings, on which an induction coil is wound, and the induction coil is located in the gap between the two magnetic guide rings; wherein, when the ferromagnetic projectile passes through the electromagnetic induction speed measuring module, the projectile causes a change in the magnetic flux of the magnetic circuit, thereby generating an induced electromotive force in the induction coil.

[0009] Furthermore, the electromagnetic induction speed measuring device includes three electromagnetic induction speed measuring modules arranged sequentially along the projectile's flight direction, and the induction coils of the three speed measuring modules are electrically connected in series.

[0010] Furthermore, it also includes a low-pass filter, the input of which is electrically connected to the series-connected induction coil, and the output of which is connected to a signal output interface for outputting the filtered induced voltage signal to an external acquisition device.

[0011] Furthermore, the base of the gun barrel vacuum assembly is a stainless steel base with multiple threaded holes around it, and the third interface is one or more of the threaded holes.

[0012] Furthermore, the vacuuming device includes a vacuum gauge and a vacuum pump; the third interface includes two threaded holes, which are respectively connected to the vacuum gauge and the vacuum pump through a vacuum valve and a sealing gasket; the unused threaded holes are sealed with plugs and sealing gaskets.

[0013] Furthermore, it also includes a polycarbonate connecting pipe, one end of which is sealed to the second interface of the base, and the other end of which passes through the internal cavity of the electromagnetic induction velocity detector and is sealed and fixed to the outer shell of the velocity detector, thereby forming an air passage connection between the gun barrel vacuum assembly and the electromagnetic induction velocity detector, and providing a flight channel for the projectile.

[0014] The present invention also provides a light air gun system, including a light air gun barrel, and a light air gun barrel vacuum assembly with electromagnetic induction velocity measurement function as described above, wherein the first interface of the base of the assembly is coaxially and sealed to the muzzle of the light air gun barrel.

[0015] This invention also provides a method for magnetic induction velocity measurement and barrel vacuuming, using the aforementioned light gas gun barrel vacuuming assembly with electromagnetic induction velocity measurement function. The method includes the following steps: S1, sealingly connecting the base of the barrel vacuum assembly to the light gas gun barrel; S2, connecting the electromagnetic induction velocity meter to the barrel vacuum assembly via a connecting pipe to form the sealed gas path; S3, activating the vacuuming device connected to the base to vacuum the sealed gas path; S4, after the vacuum level in the sealed gas path reaches a preset value, shutting off the vacuuming device; S5, launching a ferromagnetic projectile, which accelerates along the barrel and enters the internal cavity of the electromagnetic induction velocity meter; S6, using at least two electromagnetic induction velocity measuring modules inside the electromagnetic induction velocity meter to sequentially generate induction signals characterizing the projectile's passage; S7, an external acquisition system acquires the induction signals and calculates the projectile's velocity based on the known distance between adjacent velocity measuring modules and the signal time difference.

[0016] The vacuum pumping assembly and application method for a lightweight gas cannon barrel with electromagnetic induction velocity measurement function of the present invention have the following advantages: This invention revolutionizes projectile attitude stability by deeply integrating a vacuum-generating function with an electromagnetic induction velocimeter, eliminating the physical basis for muzzle turbulence at its source. Comparative experiments show that without a vacuum, muzzle turbulence causes a projectile attitude angle deviation of up to 3.66° within the imaging plane after exiting the barrel; however, after vacuuming using this invention, this deviation is sharply reduced to 0.99°, improving attitude stability by approximately 73%. Furthermore, in the direction outside the imaging plane, the projectile exhibits a clearly perceptible deflection without a vacuum, while no perceptible deflection is observed after vacuuming. This qualitative leap is of decisive significance for impact experiments that rely on high-precision projectile attitude control.

[0017] The inherent advantages of electromagnetic induction speed measurement are fully preserved: This invention does not change the internal mechanism of electromagnetic induction speed measurement, thus fully retaining all its advantages such as non-contact measurement, low cost, robust structure, immunity to interference from microparticles and smoke, and response only to ferromagnetic projectiles.

[0018] This invention provides an integrated and synergistic solution: it is not merely a simple combination of a "velocity sensor" and a "vacuum pump," but rather integrates them into a functionally synergistic whole through a specially designed base and a through-type connecting pipe. Vacuuming not only improves attitude stability but also reduces aerodynamic drag within the barrel, thus contributing to higher firing speed and consistency; velocity measurement is performed in a clean vacuum environment, resulting in a purer and more reliable signal. The two complement each other perfectly.

[0019] Compact structure, low modification cost, and strong applicability: This invention has a compact structure and enables rapid upgrading and modification of a large number of existing conventional light gas guns that do not have vacuum pumping capabilities at a low cost. It greatly expands the application scenarios of electromagnetic induction velocity measurement technology and has extremely high engineering practical value and broad prospects for promotion. Attached Figure Description

[0020] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 The diagram shown is a schematic representation of the overall structure of the present invention.

[0021] Figure 2 Displayed as Figure 1 A schematic diagram of the vacuum assembly of the gun barrel.

[0022] Figure 3 Displayed as Figure 1 An exploded view of the overall structure of the electromagnetic induction velocimeter.

[0023] Figure 4 Displayed as Figure 3 A schematic diagram of the exploded structure of a single electromagnetic induction speed measurement module.

[0024] Figure 5 Displayed as Figure 4 Axial cross-sectional view of the assembled electromagnetic induction speed measuring module.

[0025] Figure 6 The diagram shows the circuit connections and signal output topology in this invention.

[0026] Figure 7 The diagram shows a typical induced voltage waveform output by the electromagnetic induction speed measurement module in this invention.

[0027] Figure 8 The image shows a comparison of the projectile's flight attitude before (a) and after (b) vacuuming of the gun barrel in this invention.

[0028] Component labeling explanation: 1. Lightweight air cannon system; 2. Electromagnetic induction velocity measurement and cannon barrel vacuum assembly; 3. Vacuum pump; 4. Vacuum gauge; 5. Oscilloscope; 211. Stainless steel base; 212. Vacuum valve; 213. PTFE gasket; 214. Plug; 215. Polycarbonate tube; 221. Electromagnetic induction velocity measurement module; 222. Passive filter; 223. Positioning pin; 224. Electromagnetic induction velocity measuring device housing base plate; 225. Electromagnetic induction velocity measuring device housing side plate; 226. Electromagnetic induction velocity measuring device housing rear cover plate; 227. Electromagnetic induction velocity measuring device housing front cover plate; 228. Airtight cover plate; 2211. Permanent magnet; 2212. Magnetic ring; 2213. Polycarbonate insulating ring; 2214. Resin frame; 2215. Magnetic induction coil; 2216. Aluminum alloy bracket; 2217. Aluminum alloy bracket cover plate. Detailed Implementation

[0029] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0030] like Figures 1 to 8As shown, this invention provides a vacuum assembly for a light gas cannon barrel with electromagnetic induction velocity measurement function, comprising: an electromagnetic induction velocity measuring device for measuring the velocity of a ferromagnetic projectile, having an internal cavity through which the projectile passes; and a barrel vacuum assembly including a base, the base having a first interface for coaxial and sealed connection with the light gas cannon barrel, and a second interface communicating with the air passage of the internal cavity, the base also having at least one third interface for connecting a vacuum pumping device; when the vacuum pumping device is working, the light gas cannon barrel, the barrel vacuum assembly, and the internal cavity of the electromagnetic induction velocity measuring device form a sealed air passage that can be evacuated as a whole. In a preferred embodiment, the electromagnetic induction velocity measuring device includes a housing and at least two electromagnetic induction velocity measuring modules 221 sequentially fixed within the housing along the projectile's flight direction, for generating a time difference signal characterizing the time difference between the projectile passing through two adjacent velocity measuring modules. The electromagnetic induction speed measuring module 221 includes: a permanent magnet ring 2211 for providing a static bias magnetic field; two magnetically conductive rings 2212 respectively disposed on both sides of the permanent magnet ring 2211 for converging the magnetic field; and an insulated coil support disposed between the two magnetically conductive rings 2212, on which an induction coil is wound, and the induction coil is located in the gap between the two magnetically conductive rings 2212. When the ferromagnetic projectile passes through the electromagnetic induction speed measuring module 221, the projectile causes a change in the magnetic flux of the magnetic circuit, generating an induced electromotive force in the induction coil. The electromagnetic induction speed measuring device includes three electromagnetic induction speed measuring modules 221 arranged sequentially along the projectile's flight direction, with the induction coils of the three modules electrically connected in series. It also includes a low-pass filter 222, the input end of which is electrically connected to the series-connected induction coils, and the output end is connected to a signal output interface for outputting the filtered induced voltage signal to an external acquisition device. The base of the gun barrel vacuum assembly is a stainless steel base 211 with multiple threaded holes around its perimeter. The third interface is one or more of these threaded holes. The vacuuming device includes a vacuum gauge 4 and a vacuum pump 3. The third interface includes two threaded holes, which are connected to the vacuum gauge 4 and the vacuum pump 3 respectively via a vacuum valve 212 and a sealing gasket. Unused threaded holes are sealed with plugs 214 and sealing gaskets. A polycarbonate connecting pipe is also included. One end of the connecting pipe is sealed to the second interface of the base, and the other end passes through the internal cavity of the electromagnetic induction velocity detector and is sealed and fixed to the outer shell of the velocity detector, thereby forming an air passage connection between the gun barrel vacuum assembly and the electromagnetic induction velocity detector, and providing a flight path for the projectile.

[0031] The present invention also provides a light air gun system 1, including a light air gun barrel, and the aforementioned light air gun barrel vacuum assembly with electromagnetic induction speed measurement function, wherein the first interface of the base of the assembly is coaxially and sealedly connected to the muzzle of the light air gun barrel.

[0032] This invention also provides a method for magnetic induction velocity measurement and barrel vacuuming, using the aforementioned light gas gun barrel vacuuming assembly with electromagnetic induction velocity measurement function. The method includes the following steps: S1, sealing the base of the barrel vacuum assembly to the light gas gun barrel; S2, connecting the electromagnetic induction velocity meter to the barrel vacuum assembly via a connecting pipe to form the sealed gas path; S3, activating the vacuuming device connected to the base to vacuum the sealed gas path; S4, after the vacuum level in the sealed gas path reaches a preset value, turning off the vacuuming device; S5, launching a ferromagnetic projectile, which accelerates along the barrel and enters the internal cavity of the electromagnetic induction velocity meter; S6, using at least two electromagnetic induction velocity measuring modules 221 inside the electromagnetic induction velocity meter to sequentially generate induction signals characterizing the projectile's passage; S7, an external acquisition system acquires the induction signals and calculates the projectile's velocity based on the known distance between adjacent velocity measuring modules and the signal time difference.

[0033] The following description uses a specific embodiment as an example: like Figure 1 As shown, this embodiment provides a vacuum pumping assembly for a light gas cannon barrel with electromagnetic induction velocity measurement, specifically designed to upgrade the functionality of a conventional light gas cannon system 1 that lacks its own vacuum pumping capability. The assembly comprises two main parts: an electromagnetic induction velocity meter and a barrel vacuum assembly, connected to the projectile's path via a polycarbonate tube 215. During system operation, a vacuum pump 3 evacuates the system, the electromagnetic induction velocity meter measures the projectile's velocity, and the generated signal is acquired by an oscilloscope 5.

[0034] First, combined Figure 2The composition of the gun barrel vacuum assembly is described in detail. The main body of the assembly is a stainless steel base 211, one end of which is machined with a coaxial thread, serving as the first interface for a secure and sealed connection to the gun barrel of the light gas gun. Four threaded holes are evenly machined around the base, serving as a universal third interface for connecting vacuum components. In the actual layout of this embodiment, due to space constraints, two threaded holes are inconvenient for connecting pipelines; therefore, stainless steel plugs 214 and PTFE gaskets 213 are used to tightly seal them. The remaining two threaded holes are then sealed and connected, via a vacuum valve 212 and PTFE gaskets 213, to a vacuum gauge 4 for real-time vacuum display and a vacuum pump 3 for generating vacuum, respectively. A polycarbonate connecting tube, its tail precisely inserted into the central hole (i.e., the second interface) of the stainless steel base 211 and fixed in place, its material ensuring sufficient strength and a smooth inner surface to serve as a flight path for the projectile.

[0035] Next, combined Figures 3 to 5 The structure of the electromagnetic induction speed measuring device is explained. For example... Figure 3 As shown, the velocity detector has an aluminum alloy shell assembled from a base plate, side plates, a rear cover plate 226, and a front cover plate 227. Inside the shell, three identical electromagnetic induction velocity measuring modules 221 are installed at equal intervals along the projectile's flight axis. These modules are precisely positioned using two stainless steel positioning pins 223 and firmly fixed to the base plate 224 of the shell with M6 bolts, ensuring the concentricity and spacing accuracy of the modules. The aforementioned polycarbonate connecting pipe passes sequentially through the front cover plate 227, the central through-hole of the three velocity measuring modules, and the rear cover plate 226, with its front end finally pressed and fixed by the front cover plate 227. An airtight cover plate 228 is also provided outside the front cover plate 227, together with the other two holding a PE film to provide auxiliary sealing for the velocity detector outlet. Thus, an airtight and smooth integrated ballistic / air path channel is constructed from the barrel, through the base, the polycarbonate pipe 215, to the PE film. A 1MHz high-order passive filter 222, which serves as a low-pass filter 222, is also fixed inside the housing for signal filtering.

[0036] Figure 4 and Figure 5The internal structure of the speed measuring module is shown in detail, which is a layered structure symmetrical about its axis. At the center is a permanent magnet ring 2211 made of neodymium magnet material, providing a static bias magnetic field. At each axial end of the permanent magnet ring 2211, a soft magnetic guide ring 2212 made of high-permeability low-carbon steel is tightly attached. These two guide rings 2212 efficiently concentrate and guide the magnetic field generated by the permanent magnet 2211 to its inner ring region. In the annular space between the two guide rings 2212, an insulated coil support made of PEEK resin material is precisely placed. The enameled wire induction coil on the guide ring 2212 is wound on this support, and the coil is suspended precisely in the center of the narrow annular gap formed by the opposite end faces of the two guide rings 2212. This location is the region with the largest and most dramatic magnetic field gradient. Further outwards are two polycarbonate insulating pads, respectively attached to the outer side of the guide rings 2212. Finally, the clamp, consisting of aluminum alloy bracket 2216 and aluminum alloy bracket cover plate 2217, firmly clamps all the aforementioned internal parts from both sides with bolts, forming a pre-tightened, stable, modular assembly that can be installed and replaced as a whole.

[0037] Regarding signal acquisition and processing, such as Figure 6 As shown in the circuit topology diagram, in this embodiment, the induction coils of the three speed measurement modules are connected in series. The wires at both ends of the series-connected coils are connected to the input terminal of a 1MHz low-pass filter 222. The function of the filter 222 is to filter out various high-frequency electromagnetic interferences (such as discharge noise from the drive power supply) that may exist in the experimental environment, so as to improve the signal-to-noise ratio. The output terminal of the filter 222 is soldered to a base with a standard BNC connector. This base is fixed to the housing and serves as a unified signal output interface, facilitating connection to external acquisition systems such as an oscilloscope 5 using a coaxial cable.

[0038] The complete workflow of the application method of this invention is as follows: System Assembly and Sealing: Following the aforementioned method, tighten the stainless steel base 211 onto the muzzle of the light gas cannon, and connect and fix the electromagnetic induction velocimeter to the base via the polycarbonate tube 215, ensuring a reliable seal at all interfaces. Vacuuming: Open the vacuum valve 212 connected to the vacuum pump 3, and start the vacuum pump 3 to evacuate the entire sealed gas path consisting of the cannon barrel, base, polycarbonate tube 215, and the inside of the velocimeter housing. During this period, monitor the vacuum level within the system in real time using the vacuum gauge 4. Pressure Holding: Once the vacuum level reaches the experimental preset requirement, for example, close to absolute vacuum, first close the vacuum valve 212 connected to the vacuum pump 3, then stop the vacuum pump 3, ensuring that the system maintains a high vacuum state.

[0039] Launch and Measurement: The light gas cannon is activated, and high-pressure gas propels the ferromagnetic projectile, accelerating it along the barrel. The projectile then enters the polycarbonate tube 215 and sequentially passes at high speed through the center of the three electromagnetic induction velocity measurement modules 221. Signal Generation and Acquisition: As... Figure 7 As shown, when the ferromagnetic material portion of the projectile enters and exits the coil plane of each velocity-measuring module, it causes a drastic change in the magnetic flux of the magnetic circuit, thereby inducing a pair of voltage pulses of opposite polarity in the series coil. As the projectile passes through the three modules sequentially, it generates three sets (a total of six characteristic peaks) of induced voltage waveforms that are sequentially ordered. These raw signals are processed by a 1MHz low-pass filter 222, becoming... Figure 7 The smooth pulse waveform shown is transmitted to oscilloscope 5 via a BNC interface. Velocity calculation: Assume the known precise distance between two adjacent velocity measurement modules is L. Read the pulse time difference Δt1 generated by the projectile passing through the first and second modules, and the time difference Δt2 between the second and third modules, from the waveform recorded by oscilloscope 5. Then, the average velocity of the projectile between the first and second modules is v1 = L / Δt1, and the average velocity between the second and third modules is v2 = L / Δt2. Finally, the average value of these two values, v = 2L / (Δt1 + Δt2), can be taken as the precise muzzle velocity of the projectile in the velocity measurement section. Finally, through... Figure 8 The comparison visually demonstrates the decisive technical effects of the present invention. Figure 8 Images (a) and (b) are high-speed photographs of the projectile's attitude after exiting the barrel, taken without vacuum and with vacuum applied using the present invention, respectively, while keeping all other experimental conditions the same. It can be clearly seen that under the condition of no vacuum ( Figure 8 a) The pre-exploded high-pressure airflow creates complex turbulence within the velocity sensor, exerting a significant disturbance torque on the projectile, causing a visible random deflection of the projectile's attitude. However, after applying this invention to perform vacuuming ( Figure 8 (b) Because the gas medium that generates turbulence is completely eliminated, the projectile's flight attitude is extremely stable throughout the entire velocity measurement range, with almost no observable deflection. Quantitative analysis data shows that the root mean square deviation of the projectile's attitude angle within the imaging plane is significantly reduced from 3.66° before vacuuming to 0.99° after vacuuming, representing an improvement in attitude stability of approximately 73%. This fully demonstrates the effectiveness and superiority of the technical solution of this invention.

[0040] Therefore, the vacuum pumping assembly and application method for a light gas gun barrel with electromagnetic induction velocity measurement function provided by this invention creatively proposes a collaborative working concept of "vacuuming first, then measuring velocity," integrating the barrel vacuum pumping assembly and the electromagnetic induction velocity measuring device into a single unit. Its working mechanism lies in the fact that, before firing, the entire sealed gas path consisting of the barrel, vacuum assembly, and velocity measuring device is evacuated. This completely eliminates the possibility of premature ejection of gas medium from a physical perspective, ensuring that no gas interacts with the velocity measuring device structure when the projectile leaves the barrel, thereby completely avoiding muzzle turbulence and ensuring the stability of the projectile's attitude. Simultaneously, vacuuming also reduces the aerodynamic drag of the projectile within the barrel, which is beneficial for improving muzzle velocity and velocity consistency.

[0041] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A vacuum pumping assembly for a light gas gun barrel with electromagnetic induction velocity measurement function, characterized in that, include: An electromagnetic induction velocity measuring device for measuring the velocity of a ferromagnetic projectile has an internal cavity through which the projectile passes. A gun barrel vacuum assembly includes a base having a first interface for coaxial sealing connection with a light gas gun barrel and a second interface communicating with the internal cavity gas passage. The base also has at least one third interface for connecting a vacuum pumping device. When the vacuum pumping device is working, the internal cavity of the light gas cannon barrel, the barrel vacuum assembly, and the electromagnetic induction velocimeter forms a sealed gas path that can be evacuated as a whole.

2. The vacuum pumping assembly for a light gas cannon barrel with electromagnetic induction velocity measurement function according to claim 1, characterized in that, The electromagnetic induction velocity measuring device includes a housing and at least two electromagnetic induction velocity measuring modules (221) that are sequentially fixed inside the housing along the projectile's flight direction, for generating a time difference signal characterizing the projectile's passage through two adjacent velocity measuring modules.

3. The vacuum pumping assembly for a light gas cannon barrel with electromagnetic induction velocity measurement function according to claim 2, characterized in that, The electromagnetic induction speed measuring module (221) includes: A permanent magnet (2211) ring is used to provide a static bias magnetic field; Two magnetic rings (2212) are respectively disposed on both sides of the axial direction of the permanent magnet (2211) ring to converge the magnetic field; An insulated coil support is disposed between the two magnetic rings (2212), on which an induction coil is wound, and the induction coil is located in the gap between the two magnetic rings (2212); When the ferromagnetic projectile passes through the electromagnetic induction speed measuring module (221), the projectile causes a change in the magnetic flux of the magnetic circuit, which in turn generates an induced electromotive force in the induction coil.

4. The vacuum pumping assembly for a light gas cannon barrel with electromagnetic induction velocity measurement function according to claim 3, characterized in that, The electromagnetic induction speed measuring device includes three electromagnetic induction speed measuring modules (221) arranged sequentially along the projectile's flight direction, and the induction coils of the three speed measuring modules are electrically connected in series.

5. The vacuum pumping assembly for a light gas gun barrel with electromagnetic induction velocity measurement function according to claim 4, characterized in that, It also includes a low-pass filter (222), the input of which is electrically connected to the series-connected induction coil, and the output is connected to a signal output interface for outputting the filtered induced voltage signal to an external acquisition device.

6. The vacuum pumping assembly for a light gas cannon barrel with electromagnetic induction velocity measurement function according to claim 3, characterized in that, The base of the gun barrel vacuum assembly is a stainless steel base (211) with multiple threaded holes around it, and the third interface is one or more of the threaded holes.

7. The vacuum pumping assembly for a light gas gun barrel with electromagnetic induction velocity measurement function according to claim 6, characterized in that, The vacuuming device includes a vacuum gauge (4) and a vacuum pump (3); the third interface includes two threaded holes, which are connected to the vacuum gauge (4) and the vacuum pump (3) respectively through a vacuum valve (212) and a sealing gasket; the unused threaded holes are sealed by a plug (214) and a sealing gasket.

8. The vacuum pumping assembly for a light gas gun barrel with electromagnetic induction velocity measurement function according to any one of claims 1 to 7, characterized in that, It also includes a polycarbonate connecting pipe, one end of which is sealed to the second interface of the base, and the other end of which passes through the internal cavity of the electromagnetic induction velocity detector and is sealed and fixed to the outer shell of the velocity detector, thereby forming an air passage connection between the gun barrel vacuum assembly and the electromagnetic induction velocity detector, and providing a flight channel for the projectile.

9. A lightweight air cannon system, comprising a lightweight air cannon barrel, characterized in that, It also includes a vacuum assembly for a light gas gun barrel with electromagnetic induction velocity measurement function according to any one of claims 1 to 8, wherein the first interface of the base of the assembly is coaxially and sealed to the muzzle of the light gas gun barrel.

10. A method for magnetic induction velocity measurement and gun barrel vacuuming, characterized in that, The method of using the vacuum pumping assembly for a light gas gun barrel with electromagnetic induction velocity measurement function as described in any one of claims 1 to 8 includes the following steps: S1. Seal and connect the base of the gun barrel vacuum assembly to the light gas gun barrel. S2. Connect the electromagnetic induction velocity measuring device and the gun barrel vacuum assembly through a connecting pipe to form the sealed gas path; S3. Start the vacuum equipment connected to the base to perform vacuuming on the sealed gas path; S4. After the vacuum level in the sealed gas path reaches the preset value, turn off the vacuum pumping equipment. S5. Launch a ferromagnetic projectile, which accelerates along the barrel and enters the internal cavity of the electromagnetic induction velocity sensor. S6. Using at least two electromagnetic induction speed measuring modules (221) inside the electromagnetic induction speed measuring device, induction signals characterizing the passing of the projectile are generated sequentially. S7. The external acquisition system acquires the sensing signal and calculates the velocity of the projectile based on the known distance between adjacent velocity measurement modules and the signal time difference.

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