Underwater projectile speed test system and method and underwater projectile position estimation system and method

Abstract

The invention provides an underwater projectile speed testing system, and belongs to the field of projectile speed measurement, the underwater projectile speed testing system comprises at least two first detection devices arranged along the motion direction of a projectile, each first detection device comprises an excitation coil and at least one induction coil bridged on the excitation coil, pulse excitation current is introduced into the excitation coil, and the excitation coil is connected with the at least one induction coil; when the projectile moves to the position over the induction coil, the induction voltage in the induction coil is changed from negative to positive; the invention further provides an underwater projectile speed test method and an underwater projectile position estimation system and method. The speed of the projectile can be obtained by measuring the time when the induced voltages of the induction coils in the two first detection devices are changed from negative to positive and combining the distance between the two first detection devices. The projectile does not need to penetrate through the coil, the cavitation form and the motion state of the projectile are not influenced, the influence of external conditions such as water turbidity and illumination is avoided, and repeated measurement can be carried out.

Description

Technical Field

[0001] The present invention relates to the technical field of projectile velocity measurement, and in particular to an underwater projectile velocity testing system and method, and a position estimation system and method. Background Art

[0002] Underwater projectile speed testing is of great significance in the military and industrial fields. The speed of underwater projectiles is an important indicator for evaluating the range and lethality of underwater projectiles. For example, supercavitating projectiles developed using supercavitation technology can achieve high-speed movement of projectiles underwater, so as to maintain a long range and destructive kinetic energy for the projectiles underwater.

[0003] Traditional coil targets and aluminum foil targets are widely used to measure projectile velocity in air, but both have obvious limitations in underwater environments. Existing coil targets are usually ring-shaped, and use the electromagnetic induction phenomenon generated by the projectile passing through the ring to achieve projectile velocity testing. They are mostly used to measure velocity near the muzzle. When measuring velocity far from the muzzle, there may be deviations in the ballistic trajectory that prevent the projectile from passing through the coil target ring, resulting in the inability to measure velocity. Aluminum foil target velocity measurement devices can be used to measure projectile velocity in water, but they will affect the cavitation morphology and the stability of the projectile's underwater motion. In addition, aluminum foil velocity measurement targets can only measure the velocity of a single shot projectile, cannot be reused, and are less efficient.

[0004] In addition, other methods for testing underwater projectile speed include light curtain targets, high-speed photography, and Doppler sonar. However, these methods also have different drawbacks. Both the light curtain target speed measurement method and the high-speed photography method require an external light source. In highly turbid waters, due to the large attenuation and severe scattering of light in water, the effective detection area of ​​both laser light curtains and infrared light curtains is usually small. The images taken underwater by the high-speed photography method have low resolution and large image distortion, requiring complex algorithms for correction. In addition, the wake and bubbles of the supercavitating projectile can also distort the optical path, affecting the speed measurement accuracy. Although the Doppler sonar method does not require an external light source and is not affected by underwater magnetic objects, it is difficult to capture short-term signals, the speed measurement range is limited, and it is easy to detect other non-test objects, making it difficult to distinguish between target signals and interference signals.

[0005] In the prior art, the Chinese invention patent application with publication number CN110852008A, "An electromagnetic measurement method for the velocity of a projectile during the impact and extrusion of a countersunk bullet," can calculate the velocity of a projectile during the impact and extrusion of a countersunk bullet. This method essentially uses a traditional coil target to measure the velocity of a projectile. If it is used to measure the velocity of a projectile in an underwater environment, there is a problem: when measuring the velocity away from the muzzle, there may be a deviation in the ballistic trajectory that prevents the projectile from passing through the coil target ring, resulting in the inability to measure the velocity. Summary of the Invention

[0006] The technical problem to be solved by the present invention is how to measure the speed of an underwater projectile.

[0007] The present invention solves the above technical problems through the following technical solutions: an underwater projectile speed testing system, the system includes at least two detection devices arranged along the direction of projectile movement, each detection device includes an excitation coil and at least one induction coil connected across the excitation coil, a pulse excitation current is passed through the excitation coil, and when the projectile moves to just above the induction coil, the induced voltage in the induction coil changes from negative to positive.

[0008] Beneficial Effects: The pulsed excitation current generates a pulsed electromagnetic field. After the current is turned off, eddy currents are generated inside the projectile, generating an induced electromagnetic field. The induction coil senses the electromagnetic field changes caused by the projectile's eddy currents in space, generating an induced voltage. By measuring the time it takes for the induced voltage in the induction coils of the two detection devices to change from negative to positive, combined with the distance between the two detection devices, the projectile velocity can be determined. The projectile does not need to pass through the coil, which does not affect the projectile's cavitation morphology or motion. It is unaffected by external conditions such as water turbidity and light, and can be measured repeatedly.

[0009] Preferably, the induced voltage in the induction coil is the sum of the induced voltage generated in the induction coil by the pulse excitation current during the off time and the induced voltage generated in the induction coil by the eddy current effect of the projectile.

[0010] Preferably, when the vertical distance between the center of the excitation coil and the center of the induction coil meets the set distance, the induced voltage in the induction coil is approximately equal to the induced voltage generated in the induction coil by the eddy current effect of the projectile.

[0011] Beneficial effect: The vertical distance between the center of the excitation coil and the center of the induction coil meets the set distance, which can make the induced voltage generated during the off-time of the pulse excitation current as small as possible, thereby reducing the interference of the induced voltage generated by the pulse excitation current in the induction coil on the induced voltage generated by the projectile eddy current effect in the induction coil. At this time, the induced voltage in the induction coil is approximately the induced voltage generated by the projectile eddy current effect in the induction coil, which can facilitate better measurement of the induced voltage generated by the eddy current.

[0012] Preferably, the excitation coil is rectangular and the induction coil is circular, and both are eccentric structures. The excitation coil includes an external wire frame 1 and an excitation coil winding wound on the external wire frame 1, and the induction coil includes an external wire frame 2 and an induction coil winding wound on the external wire frame 2.

[0013] Preferably, the excitation coil is connected to an excitation current generator and a control unit, and the induction coil is connected to a multi-channel receiver module. The excitation current generator and the control unit include a power supply module, a charging module and a discharge module. The discharge module provides a pulse excitation current to the excitation coil by controlling the charging module; the multi-channel receiver module includes a matching circuit, an analog-to-digital conversion circuit, a communication circuit and a host computer. The matching circuit limits the induced voltage, and the limited induced voltage is converted into a digital signal through the analog-to-digital conversion circuit. The communication circuit transmits the digital signal to the host computer.

[0014] The present invention also provides an underwater projectile speed testing method, which uses an underwater projectile speed testing system. The method includes: calculating the time difference according to the moment corresponding to the inflection point when the induced voltage in the induction coil changes from negative to positive, and calculating the projectile speed according to the distance and time difference between the two detection devices.

[0015] Preferably, the projectile velocity v is calculated as:

[0016]

[0017] Among them, S is the distance between the two detection devices, T1 and T2 are the times corresponding to the inflection points when the induced voltage in the induction coil changes from negative to positive when the projectile passes through the two detection devices one by one.

[0018] Preferably, the induced voltage U(t) in the induction coil is calculated as follows:

[0019]

[0020] Among them, U1(t) is the induced voltage generated by the pulse excitation current in the induction coil during the off time, U2(t) is the induced voltage generated by the eddy current effect of the projectile in the induction coil during the off time, I0 is the excitation current, dl1 is the excitation coil wire element, B1(r0) is the magnetic induction intensity of the magnetic field generated by the pulse excitation current at the induction coil, r0 is the distance vector between the excitation coil and the induction coil, B1(r1) is the magnetic induction intensity of the magnetic field generated by the pulse excitation current at the projectile magnetic dipole, r1 is the distance vector between the excitation coil and the projectile, B2(r2) is the magnetic induction intensity of the magnetic field generated by the eddy current at the induction coil, r2 is the distance vector between the projectile and the induction coil, e r0 ,e r2 is a unit vector, m is the dipole moment of the projectile, G is the Green's function that is only related to the position, M is the magnetic polarizability tensor matrix of the projectile target, which is related to the shape, size, orientation, magnetic permeability and electrical conductivity of the target, and μ is the underwater magnetic permeability.

[0021] The present invention also provides an underwater projectile position estimation system, including an underwater projectile speed testing system. The position estimation system also includes a detection device 2 arranged vertically to the detection device 1 and with an adjustable distance. The detection device 2 includes an excitation coil and at least one induction coil connected across the excitation coil. The central axis of the induction coil in the detection device 1 intersects vertically with the central axis of the induction coil in the detection device 2.

[0022] The present invention also provides an underwater projectile position estimation method, which uses an underwater projectile position estimation system. The method includes: establishing a database of the relationship between the induced voltage and the projectile coordinate position based on the change in the induced voltage amplitude at different vertical distances between the projectile and the induction coil, comparing the measured induced voltage with the database, and estimating the projectile position.

[0023] The advantages provided by the present invention are:

[0024] 1. The underwater projectile velocity testing system of the present invention can adjust the detection capability by changing parameters such as coil size, number of coils, current amplitude, and distance between devices according to the size of the projectile to meet the speed measurement requirements of different types of projectiles; by setting up multiple detection devices, it can measure the velocity of the projectile in multiple displacement segments, and by setting multiple induction coils on each excitation coil, it is ensured that the projectile velocity can still be tested when the projectile trajectory deviates, further improving the accuracy of the projectile velocity test.

[0025] 2. The underwater projectile position estimation system of the present invention can estimate the projectile position while detecting the projectile speed. The current amplitude, current frequency and coil radius can be adjusted according to the size of the projectile to realize the measurement and position estimation of the velocity parameters of projectiles of different projectile types. By setting up multiple detection devices to continuously detect the underwater motion trajectory of the projectile, multiple induction coils can be installed on an excitation coil to ensure that the projectile speed and position can still be tested when the projectile trajectory deviates, so as to obtain more accurate projectile data, and the system has strong scalability. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic diagram of an underwater projectile velocity testing system provided in Example 1 of the present invention;

[0027] Figure 2 A schematic diagram of a detection device 1 in an underwater projectile velocity testing system provided in Example 1 of the present invention;

[0028] Figure 3 Schematic diagram of an excitation coil in an underwater projectile velocity testing system provided in Example 1 of the present invention;

[0029] Figure 4 A schematic diagram of an induction coil in an underwater projectile velocity testing system provided in Example 1 of the present invention;

[0030] Figure 5 A schematic diagram of a bracket in an underwater projectile velocity testing system provided in Example 1 of the present invention;

[0031] Figure 6 A schematic diagram of an underwater projectile position estimation system provided in Example 3 of the present invention;

[0032] Figure 7 A schematic diagram of a bracket in an underwater projectile position estimation system provided in Example 3 of the present invention;

[0033] Figure 8 Schematic diagram of an underwater projectile position estimation system provided in Example 3 of the present invention, in which two induction coils are provided on each excitation coil;

[0034] Figure 9 Schematic diagram of an excitation current generator and a control unit in an underwater projectile velocity testing system provided in Example 1 of the present invention;

[0035] Figure 10 Schematic diagram of the pulse excitation current in the underwater projectile velocity testing system provided in Example 1 of the present invention;

[0036] Figure 11 A diagram showing the working principle of the underwater projectile velocity testing system provided in Example 1 of the present invention;

[0037] Figure 12 A schematic diagram showing the relationship between the logarithm of the absolute value of the induction coil voltage and time when a projectile is present and when a projectile is not present in the underwater projectile velocity test system provided by Example 1 of the present invention;

[0038] Figure 13 Schematic diagram of the voltage waveform of the induction coil when a projectile passes through or not in the underwater projectile velocity testing system provided by Example 1 of the present invention;

[0039] Figure 14 Schematic diagram of the underwater projectile velocity testing method provided in Example 2 of the present invention;

[0040] Figure 15 This is a schematic diagram of the working of the underwater projectile position estimation system provided in Example 3 of the present invention;

[0041] Figure 16 A schematic diagram showing the relationship between the induced voltage and the vertical distance between the projectile and the induction coil when the projectile passes directly above the induction coil in the underwater projectile position estimation method provided in Example 4 of the present invention;

[0042] In the figure: 1 detection device 1, 10 excitation coil, 11 external wire frame 1, 12 excitation coil winding, 20 induction coil, 21 external wire frame 2, 22 induction coil winding, 2 detection device 2, 3 excitation current generator and control unit, 31 power supply module, 311 lithium battery, 312 step-down module, 313 auxiliary power supply module, 32 charging module, 321 boost module, 322 relay, 323 energy storage capacitor, 324 control circuit module, 33 discharge module, 331 IGBT isolation drive circuit, 332 IGBT module, 333 constant voltage clamping circuit, 4 multi-channel receiver module, 5 projectile, 6 bracket, 61 first cylinder, 62 second cylinder, 63 third cylinder, 64 fourth cylinder. DETAILED DESCRIPTION

[0043] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the following describes the technical solutions of the present invention clearly and completely with reference to specific embodiments and the accompanying drawings. It is obvious that the embodiments described are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0044] Example 1

[0045] like Figure 1 As shown, this embodiment provides an underwater projectile speed testing system, including at least two detection devices 1 arranged along the moving direction of the projectile 5, each detection device 1 includes an excitation coil 10 and at least one induction coil 20 connected across the excitation coil 10, and a pulse excitation current is passed through the excitation coil 10. When the projectile 5 moves to just above the induction coil 20, the induced voltage in the induction coil 20 changes from negative to positive.

[0046] The pulse excitation current of the present invention can be used as follows Figure 10 The pulse excitation current shown is a trapezoidal short-time pulse current. The excitation coil 10 is turned on at time 0. After a time t r After that, the current reaches the maximum value I and maintains a stable current output for a duration of P W After the current is turned off, after time t f After the current is 0, the pulse excitation current stable output time P W In milliseconds, the current rise time t r and the current off time t f It is on the order of microseconds. In this embodiment, the frequency of the trapezoidal pulse current is 100 Hz.

[0047] The pulse excitation current can generate a pulse electromagnetic field. After the current is turned off, induced eddy currents are generated inside the projectile 5, thereby generating an induced electromagnetic field. The induction coil 20 senses the electromagnetic field changes caused by the projectile eddy currents in the space, thereby generating an induced voltage. The induced voltage in the induction coil 20 is the sum of the induced voltage generated in the induction coil 20 by the pulse excitation current during the off time and the induced voltage generated in the induction coil 20 by the projectile eddy current effect.

[0048] The principle of the induction coil 20 detecting the motion of the projectile 5 is to treat the projectile 5 as a conductive ring. According to Faraday's law of electromagnetic induction, the magnitude of the induced electromotive force in the conductor loop is proportional to the rate of change of the magnetic flux passing through the coil loop, that is:

[0049]

[0050] In formula (1), ψ is the magnetic flux passing through the coil loop, u is the magnitude of the induced electromotive force in the coil loop, S is the area of ​​the induction coil, and N is the number of coil turns. Therefore, the working principle of the underwater projectile velocity testing system of the present invention can be expressed as:

[0051]

[0052] In formula (2), u(t) is the total induced electromotive force of the induction coil, u1(t) is the induced electromotive force generated in the induction coil by the pulse excitation current in the excitation coil, and u2(t) is the induced electromotive force generated in the induction coil by the eddy current field of the projectile. Ψ1 is the off time of the excitation current in the excitation coil (e.g. Figure 7 The time t shown f ) is the magnetic flux of the excitation current passing through the induction coil, and Ψ2 is the magnetic flux of the eddy current electromagnetic field passing through the coil during the eddy current decay process of the projectile.

[0053] According to the magnetic dipole model theory, the distance between the induction coil 20 and the projectile 5 is much larger than the projectile size. The induction coil 20 and the projectile 5 can be approximately regarded as a single magnetic dipole model. The eddy current magnetic field generated by the projectile 5 in space can be equivalent to the eddy current magnetic field generated by the induction dipole in space.

[0054] The dipole moment of a three-dimensional orthogonal dipole is m = [m1, m2, m3]. The detection system emits an excitation field B1(r1), under which the equivalent dipole moment is m = MB1(r1). The induced magnetic field generated by a magnetic dipole with a magnetic moment of m at a position r in space is:

[0055]

[0056] In formula (3), μ is the underwater magnetic permeability. Therefore, the eddy current induced magnetic field can be expressed as:

[0057]

[0058] The induced voltage signal U(t) can be obtained from the excitation induced magnetic field and the eddy current induced magnetic field as follows:

[0059]

[0060] Among them, U1(t) is the induced voltage generated by the pulse excitation current in the induction coil during the off time, U2(t) is the induced voltage generated by the eddy current effect of the projectile in the induction coil during the off time, I0 is the excitation current, dl1 is the excitation coil wire element, B1(r0) is the magnetic induction intensity of the magnetic field generated by the pulse excitation current at the induction coil, and r0 is the distance vector between the excitation coil and the induction coil. B1(r1) is the magnetic induction intensity of the magnetic field generated by the pulse excitation current at the projectile magnetic dipole, and r1 is the distance vector between the excitation coil and the projectile. B2(r2) is the magnetic induction intensity of the magnetic field generated by the eddy current at the induction coil, and r2 is the distance vector between the projectile and the induction coil. e r0 ,e r2 is the unit vector of r0 and r2. m is the dipole moment of the projectile, G is the Green's function that is only related to the position, M is the magnetic polarizability tensor matrix of the projectile target, which is related to the shape, size, orientation, magnetic permeability, and electrical conductivity of the target, and μ is the underwater magnetic permeability.

[0061] Therefore, the induced voltage in the induction coil 20 is the sum of the induced voltage generated in the induction coil 20 by the pulse excitation current during the off-time and the induced voltage generated in the induction coil 20 by the eddy current effect of the projectile. In order to better measure the induced voltage generated by the eddy current, the induced voltage generated by the pulse excitation current needs to be as small as possible. In the present invention, the induction coil 20 is connected across the excitation coil 10, and the excitation coil 10 and the induction coil 20 form an eccentric structure, which can make the induced voltage generated during the off-time of the pulse excitation current as small as possible, thereby reducing the interference of the induced voltage generated in the induction coil 20 by the pulse excitation current on the induced voltage generated in the induction coil 20 by the eddy current effect of the projectile. At this time, the induced voltage in the induction coil 20 is approximately the induced voltage generated in the induction coil 20 by the eddy current effect of the projectile.

[0062] The working principle of the underwater projectile velocity testing system of this embodiment is described in detail below with reference to the simulation waveform diagram:

[0063] See also Figure 13 The pulse excitation current flowing into the excitation coil 10 is a trapezoidal pulse current, the maximum current is set to 80A, and the opening time t r and the off time t f They are 0.05ms respectively, and the current stable output duration P WThe time between the two detection devices 1 is 1ms, and the distance S between them is 1.5m. During the on and off process of the pulse excitation current, i.e., the rising and falling process of the current, a changing magnetic field is generated, which generates an induced voltage in the induction coil 20. When no projectile passes through, the induced voltage is the off time t f The induced voltage generated by the internal excitation current has a maximum value of U m and -U m When a projectile passes through, the projectile 5 passes through the detection space composed of two detection devices 1 in turn. When it reaches the excitation coil 10 of the first detection device 1, it is affected by the electromagnetic field of the excitation current to generate eddy currents. After a period of time, the pulse excitation current is turned off. The eddy currents in the projectile 5 form an eddy current electromagnetic field that decays with time in the space. The induction coil 20 of the first detection device 1 senses the electromagnetic field changes caused by the eddy currents of the projectile in the space, and then generates an induced voltage. The projectile 5 continues to move to the position of the second detection device 1, and is affected by the electromagnetic field of the excitation current of the excitation coil 10 in the second detection device 1, and generates eddy currents again. After a period of time, the pulse excitation current is turned off. The eddy currents in the projectile 5 form an eddy current electromagnetic field that decays with time in the space. The induction coil 20 of the second detection device 1 senses the electromagnetic field changes caused by the eddy currents of the projectile in the space, and then generates an induced voltage. The induced voltage is the excitation current off time t f The sum of the induced voltage generated by the internal excitation current and the induced voltage of the eddy current field. The maximum induced voltage is U′ m and -U′ m , when there is a projectile, the voltage of the induction coil is greater than the voltage of the induction coil when there is no projectile.

[0064] exist Figure 11 Under the conditions shown, the absolute logarithm of the induction coil voltage with and without projectiles is taken. In the present invention, the electromagnetic field generated by the pulse excitation current is called the excitation field, and the electromagnetic field generated by the eddy current is called the induction field. The logarithm of the induced voltage in the absence of projectiles decreases linearly with time, proving that the excitation field voltage exhibits exponential decay. The induced voltage change with projectiles is consistent with that without projectiles in the initial stage, after which two parabolic curves and two inflection points appear, see Figure 12 For curve 1, because the projectile is outside the induction coil, the induced voltage generated by the projectile's eddy current magnetic field in the induction coil is negative. After taking the logarithm of the absolute value, an inflection point of the induced voltage appears at time T. For curve 2, at time T′, the projectile moves to the top of the induction coil, and the induced voltage generated by the projectile's eddy current magnetic field in the induction coil becomes positive, and another inflection point appears.

[0065] exist Figure 12The diagram showing the relationship between the logarithm of the absolute value of the induced voltage and time shows that at time T', the projectile moves directly above the induction coil, generating an inflection point in the induced voltage change. After changing the projectile's velocity, the value at time T' changes, but the inflection point where the induction coil voltage changes from negative to positive remains when the projectile moves directly above the induction coil. Using this as a reference point, by measuring the time difference between the inflection points of the induction coil voltages of the two devices, the projectile's velocity can be determined by the ratio of the distance directly above the two induction coils to this time difference. The projectile velocity v is calculated as:

[0066]

[0067] Among them, S is the distance between the two detection devices, T1 and T2 are the times corresponding to the inflection points when the induced voltage in the induction coil changes from negative to positive when the projectile passes through the two detection devices one by one.

[0068] See also Figure 14 , set the distance between the two detection devices 1 to S = 1.5m, the inflection point time of the absolute value logarithmic curve of the induction coil voltage of the first detection device 1 is T1 = 3.4ms, the inflection point time of the absolute value logarithmic curve of the induction coil voltage of the second detection device 1 is T2 = 8.5ms, the projectile speed Substituting the formula, we can get the projectile velocity of 294m / s. The set projectile velocity is 300m / s, which is within the allowable error range. Therefore, this method can be used to calculate the projectile velocity.

[0069] See also Figure 1 and Figure 5 The material of the projectile 5 is metal and the shape is cylindrical. The bottom radius of the cylinder is 6 cm and the length is 17.6 cm. In this embodiment, the underwater projectile speed test system includes at least two detection devices 1 arranged along the moving direction of the projectile 5. When two detection devices 1 are set, the projectile 5 moves from Figure 1It is launched in the direction of the arrow shown in the figure, and passes through the first detection device 1 and the second detection device 1 in sequence. It can be understood that the present invention can arrange multiple detection devices 1 along the moving direction of the projectile 5, and the distance between adjacent detection devices 1 is set according to the test needs. By setting up multiple detection devices 1, the speed of multiple target displacement segments on the projectile movement trajectory can be measured. Here, taking the setting of three detection devices 1 as an example, according to the moving direction of the projectile, they are the first detection device 1, the second detection device 1 and the third detection device 1 in sequence. The first detection device 1 and the second detection device 1 are between the first detection device 1 and the second detection device 1, and the second displacement segment S2 is between the second detection device 1 and the third detection device 1. According to the time T1, T2, and T3 corresponding to the inflection point of the induced voltage in the induction coil 20 in each detection device 1 from negative to positive, the time difference T2-T1 and T3-T2 are calculated, and the speed of the projectile passing through the first displacement segment can be calculated. The speed of the projectile passing through the second displacement section

[0070] The detection device 1 is fixed on the bracket 6, which includes two first cylinders 61, two second cylinders 62 and four third cylinders 63. The first cylinder 61, the two second cylinders 62 and the four third cylinders 63 can be fixed by threaded connection. The materials of the first cylinder 61, the two second cylinders 62 and the four third cylinders 63 are all PVC, and the size can be set according to the specifications of the excitation coil 10. In this embodiment, the length of the first cylinder 61 is 1.49m and the radius is 2.4cm, the length of the second cylinder 62 is 98cm and the radius is 2cm, the length of the third cylinder 63 is 20cm and the radius is 2.4cm. When the excitation coil 10 is square, the lengths of the first cylinder 61 and the two second cylinders 62 are the same.

[0071] See also Figure 2 、 Figure 3 and Figure 4The excitation coil 10 is rectangular, and the induction coil 20 is circular. Both have an eccentric structure. The excitation coil 10 and the induction coil 20 are connected by screw threads using a fourth cylinder 64 made of PVC. The dimensions of the fourth cylinder 64 can be selected according to measurement requirements. In this embodiment, the length of the fourth cylinder 64 is 16 cm and the radius is 1.5 cm. The excitation coil 10 includes an outer wire frame 11 and an excitation coil winding 12 wound on the outer wire frame 11. The excitation coil winding 12 is connected to the excitation current generator and the control unit. In this embodiment, the excitation coil winding 12 has a total of 20 turns, and the total thickness of the outer wire frame 11 is 14 cm. The induction coil 20 includes an outer wire frame 21 and an induction coil winding 22 wound on the outer wire frame 21. The induction coil winding 22 is connected to the matching circuit. The total number of turns of the induction coil winding 22 is 100, and the total thickness of the outer wire frame 21 is 10 cm. Both the excitation coil winding 12 and the induction coil winding 22 are sealed with waterproof material. The vertical distance L between the center of the induction coil 20 and the center of the excitation coil 10 satisfies that the excitation voltage generated by the excitation current in the induction coil is less than 0.1 V. This can make the excitation field as small as possible to measure a more accurate induction field. In this embodiment, the vertical distance L between the center of the induction coil 20 and the center of the excitation coil is 55 cm.

[0072] See also Figure 1 and Figure 9 The excitation coil 10 is connected to the excitation current generator and control unit 3, and the induction coil 20 is connected to the multi-channel receiver module 4. The excitation current generator and control unit 3 is housed in a waterproof box measuring 48 cm × 24 cm × 30 cm and is used to discharge the excitation coil 10 to generate a short-duration pulse current.

[0073] The excitation current generator and control unit 3 includes a power supply module 31, a charging module 32 and a discharge module 33. The power supply module 31 includes a large-capacity lithium battery 311, a step-down module 312 and an auxiliary power supply module 313. The charging module 32 includes a boost module 321, a relay 322, a storage capacitor 323 and a control circuit module 324. The boost module is used to increase the input voltage. The discharge module 33 is used to control the rapid linear shutdown of the pulse excitation current, including an IGBT isolation drive circuit 331, an IGBT module 332 and a constant voltage clamp circuit 333. The output voltage of the lithium battery 311 is respectively input into the boost module 321 and the step-down module 312. The stepped-down voltage is The auxiliary power supply module 313 supplies power to the control circuit module 324 and the IGBT isolation drive circuit 331 respectively. The control circuit module 324 is connected to the relay, and the control relay charges the energy storage capacitor. The IGBT isolation drive circuit 331 is connected to the drive end of the IGBT module 332. The output end of the boost module 321 is connected to one end of the relay 322, and the other end of the relay 322 is connected to one end of the energy storage capacitor 323. The other end of the energy storage capacitor 323 is connected to the input end of the IGBT module 332. The output end of the IGBT module 332 is connected to the input end of the constant voltage clamping circuit 333, and the output end of the constant voltage clamping circuit 333 is connected to the excitation coil 10.

[0074] The multi-channel signal receiver 4, housed in a waterproof box measuring 60 cm × 30 cm × 40 cm, receives the voltage signal from the induction coil in detection device 1 and transmits it to a host computer for post-processing via a matching circuit module, an analog-to-digital conversion circuit module, and a communication circuit module. The input matching circuit is used for amplitude limiting. Matching resistors can be used in the matching circuit to reduce the oscillation and decay time of the induction voltage, thereby improving the system's detection capability. The analog-to-digital conversion circuit collects the voltage signal from the induction coil and converts it into a digital signal. The communication circuit module uses a fixed communication protocol to transmit the voltage signal from the analog-to-digital conversion circuit module to the host computer. The host computer primarily consists of a high-performance computer and a data interface, connected to the communication circuit via a serial port, enabling multiple functions such as real-time data acquisition, real-time data processing and display, and data reading. The signal is stored, processed, and displayed on the host computer via the communication circuit to determine the projectile velocity.

[0075] In the underwater projectile velocity testing system of the present invention, in each detection device 1, at least one induction coil 20 is provided on the excitation coil 10. Figure 1 An induction coil 20 is provided on the excitation coil 10, see Figure 8, multiple induction coils 20 can be set on the excitation coil 10. The number of induction coils 20 is set according to the test needs, while taking into account the size design of the excitation coil and the induction coil. When multiple induction coils 20 are set, multiple induction coils 20 are connected across the same side of the excitation coil 10. By setting multiple induction coils 20, when the path of the projectile 5 is offset (that is, it may deviate from the top of a certain induction coil), the eddy current field of the projectile can be tested through the adjacent induction coil. In actual applications, by testing the induced voltage of all the induction coils in each detection device 1, it is ensured that the time when the inflection point of the induced voltage change occurs can be obtained, thereby further improving the accuracy of the projectile velocity test.

[0076] The present invention does not require the projectile to pass through the coil, so it can be used to measure the speed of the projectile far away from the muzzle position. Compared with the traditional coil target speed measurement method, there is no defect that the ballistic trajectory deviation makes the projectile unable to pass through the coil target ring, resulting in the inability to measure the speed; the present invention will not affect the projectile cavitation morphology and the projectile movement state, and will not affect the stability of the projectile moving underwater. Compared with the traditional aluminum foil target testing method, the present invention can ensure the measurement accuracy; the underwater projectile speed testing system of the present invention can adjust the detection capability by changing parameters such as coil size, coil number, current amplitude, and distance between devices according to the size of the projectile. Compared with existing light curtain target, high-speed photography, Doppler sonar method and other methods, the present invention is not affected by external conditions such as water turbidity and light, can perform repeated measurements, has high testing efficiency, and has the characteristics of strong environmental adaptability, large detection range, strong anti-interference ability, and high detection accuracy.

[0077] Example 2

[0078] This embodiment provides an underwater projectile speed testing method, using the underwater projectile speed testing system of Example 1. The method includes: calculating the time difference based on the time corresponding to the inflection point when the induced voltage in the induction coil 20 changes from negative to positive, and calculating the projectile speed based on the distance and time difference between the two detection devices 1.

[0079] The projectile velocity v is calculated as:

[0080]

[0081] Where S is the distance between the two detection devices, T i , T2 is the time corresponding to the inflection point when the induced voltage in the induction coil changes from negative to positive when the projectile passes through the two detection devices in sequence.

[0082] The induced voltage U(t) in the induction coil is calculated as:

[0083]

[0084] Among them, U1(t) is the induced voltage generated by the pulse excitation current in the induction coil during the off time, U2(t) is the induced voltage generated by the eddy current effect of the projectile in the induction coil during the off time, I0 is the excitation current, dl1 is the excitation coil wire element, B1(r0) is the magnetic induction intensity of the magnetic field generated by the pulse excitation current at the induction coil, and r0 is the distance vector between the excitation coil and the induction coil. B1(r1) is the magnetic induction intensity of the magnetic field generated by the pulse excitation current at the projectile magnetic dipole, and r1 is the distance vector between the excitation coil and the projectile. B2(r2) is the magnetic induction intensity of the magnetic field generated by the eddy current at the induction coil, and r2 is the distance vector between the projectile and the induction coil. e r0 ,e r2 is the unit vector of r0 and r2. m is the dipole moment of the projectile, G is the Green's function that is only related to the position, M is the magnetic polarizability tensor matrix of the projectile target, which is related to the shape, size, orientation, magnetic permeability, and electrical conductivity of the target, and μ is the underwater magnetic permeability.

[0085] Example 3

[0086] This embodiment provides an underwater projectile position estimation system, including the underwater projectile speed testing system of embodiment 1. The position estimation system also includes a detection device 2 arranged perpendicularly to the detection device 1 and with an adjustable distance. The detection device 2 includes an excitation coil 10 and at least one induction coil 20 connected across the excitation coil 10. The central axis of the induction coil 20 in the detection device 1 intersects perpendicularly with the central axis of the induction coil 20 in the detection device 2.

[0087] See also Figure 15 and Figure 16 When the projectile 5 passes through the detection device 1 and the detection device 2 at the same speed, as the vertical distance between the projectile and the induction coil 20 increases, for example Figure 15 In the example, the vertical distance between projectile 1 and the induction coil is 50 cm, the vertical distance between projectile 2 and the induction coil is 60 cm, and the vertical distance between projectile 3 and the induction coil is 80 cm. Figure 16 The relationship between the induced voltage when the projectile passes directly above the induction coil and the vertical distance between the projectile and the induction coil is illustrated. The induced voltage value decreases accordingly when the projectile passes directly above the induction coil. According to the change in the induced voltage amplitude at different vertical distances between the projectile and the induction coil, a database of the relationship between the induction coil voltage and the projectile coordinate position can be established. By comparing the induction coil voltage measured in the experiment with the induction coil voltage in the database, the coordinates of the projectile can be estimated, and then the position of the projectile can be deduced and the projectile trajectory can be measured.

[0088] The direction of the central axis of detection device 1 is defined as the first direction, and the direction of the central axis of detection device 2 is defined as the second direction. When the projectile passes through detection device 1 and detection device 2, the relationship between the induction coil voltage in detection device 1 and the position of the projectile in the first direction can be established according to the change in the induced voltage amplitude at different vertical distances between the projectile and the induction coil in detection device 1. The relationship between the induction coil voltage in detection device 2 and the position of the projectile in the second direction can be established according to the change in the induced voltage amplitude at different vertical distances between the projectile and the induction coil in detection device 2, thereby determining the coordinate position of the projectile in the two-dimensional space composed of the first direction and the second direction.

[0089] It should be noted that the underwater projectile position estimation system of this embodiment can simultaneously measure the projectile velocity and estimate the projectile position. The detection device consisting of detection device 1 and detection device 2 2 can be set to two or more. In actual application, multiple groups of detection devices can be expanded on the projectile path, and the coordinates of multiple points on the projectile path can be obtained, and the ballistic trajectory curve can be fitted. The detection device will not affect the projectile cavitation morphology and the projectile motion state, and can improve the measurement accuracy.

[0090] One or more induction coils 20 can be set on the excitation coil 10 in detection device 1, and one or more induction coils 20 can be set on the excitation coil 10 in detection device 2 2. When multiple induction coils 20 are set, the multiple induction coils 20 are connected across the same side of the excitation coil 10. By setting multiple induction coils 20, it is ensured that the projectile position can still be estimated when the projectile trajectory deviates, further improving the accuracy of projectile position estimation. This setting will not affect the projectile velocity test. In actual use, the size of the excitation coil and induction coil and the number of induction coils can be further adjusted according to needs to achieve more accurate testing.

[0091] Detection device 1 and detection device 2 are each fixed to a bracket 6. The specific structure of bracket 6 is the same as that of Example 1. The first cylindrical body 61 of the two brackets 6 is fixedly connected by threaded fastening. The distance between detection device 1 and detection device 2, as well as the distance between each detection device, can be adjusted to meet the speed measurement and position estimation requirements of different types of projectiles.

[0092] Compared with traditional velocity measurement methods such as coil targets, aluminum foil targets, light curtain targets, high-speed photography, and Doppler sonar, the underwater projectile position estimation system of the present invention has the advantages of not requiring an external light source, having a long detection distance, being able to estimate the projectile position while detecting the projectile speed, and having a simple structure. In addition, the system can adjust the current amplitude, current frequency, and coil radius according to the size of the projectile to achieve measurement and position estimation of velocity parameters of projectiles of different projectile types. The underwater motion trajectory of the projectile can be continuously detected by setting up multiple detection devices (detection device 1 and detection device 2 2 are connected to obtain a detection device), and multiple induction coils can be installed in one device to obtain more accurate projectile data, and the system has strong scalability.

[0093] Example 4

[0094] This embodiment provides a method for estimating the position of an underwater projectile, using the underwater projectile position estimation system of Example 3. The method includes: establishing a database of the relationship between the induced voltage and the projectile coordinate position based on the change in the induced voltage amplitude at different vertical distances between the projectile 5 and the induction coil 20, comparing the measured induced voltage with the database, and estimating the projectile position.

[0095] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. Underwater projectile velocity testing system, characterized by: The system includes at least two detection devices arranged along the direction of projectile movement. Each detection device includes an excitation coil and at least one induction coil connected across the excitation coil. A pulse excitation current is passed through the excitation coil. When the projectile moves to the top of the induction coil, the induced voltage in the induction coil changes from negative to positive.

2. The underwater projectile velocity testing system according to claim 1, characterized in that: The induced voltage in the induction coil is the sum of the induced voltage generated in the induction coil by the pulse excitation current during the off time and the induced voltage generated in the induction coil by the eddy current effect of the projectile.

3. The underwater projectile velocity testing system according to claim 1, characterized in that: When the vertical distance between the center of the excitation coil and the center of the induction coil meets the set conditions, the induced voltage in the induction coil is approximately equal to the induced voltage generated in the induction coil by the eddy current effect of the projectile. The set condition is that the excitation voltage generated in the induction coil by the pulse excitation current is less than 0.1V.

4. The underwater projectile velocity testing system according to claim 1, characterized in that: The excitation coil is rectangular and the induction coil is circular, and both are eccentric structures. The excitation coil includes an external wire frame 1 and an excitation coil winding wound on the external wire frame 1, and the induction coil includes an external wire frame 2 and an induction coil winding wound on the external wire frame 2.

5. The underwater projectile velocity testing system according to claim 1, characterized in that: The excitation coil is connected to an excitation current generator and a control unit, and the induction coil is connected to a multi-channel receiver module. The excitation current generator and the control unit include a power supply module, a charging module and a discharge module. The discharge module provides a pulse excitation current to the excitation coil by controlling the charging module. The multi-channel receiver module includes a matching circuit, an analog-to-digital conversion circuit, a communication circuit and a host computer. The matching circuit limits the induced voltage, and the limited induced voltage is converted into a digital signal through the analog-to-digital conversion circuit. The communication circuit transmits the digital signal to the host computer.

6. An underwater projectile velocity testing method, comprising: Methods include: The time difference is calculated according to the time corresponding to the inflection point when the induced voltage in the induction coil changes from negative to positive, and the projectile speed is calculated according to the distance between the two detection devices and the time difference.

7. The underwater projectile velocity testing method according to claim 6, characterized in that: The projectile velocity v is calculated as: Among them, S is the distance between the two detection devices, T1 and T2 are the times corresponding to the inflection points when the induced voltage in the induction coil changes from negative to positive when the projectile passes through the two detection devices one by one.

8. The underwater projectile velocity testing method according to claim 6, characterized in that: The induced voltage U(t) in the induction coil is calculated as: Among them, U1(t) is the induced voltage generated by the pulse excitation current in the induction coil during the off time, U2(t) is the induced voltage generated by the eddy current effect of the projectile in the induction coil during the off time, I0 is the excitation current, dl1 is the excitation coil wire element, B1(r0) is the magnetic induction intensity of the magnetic field generated by the pulse excitation current at the induction coil, r0 is the distance vector between the excitation coil and the induction coil, B1(r1) is the magnetic induction intensity of the magnetic field generated by the pulse excitation current at the projectile magnetic dipole, r1 is the distance vector between the excitation coil and the projectile, B2(r2) is the magnetic induction intensity of the magnetic field generated by the eddy current at the induction coil, r2 is the distance vector between the projectile and the induction coil, e r0 ,e r2 are the unit vectors of r0 and r2, m is the dipole moment of the projectile, G is the Green's function that is only related to the position, M is the magnetic polarizability tensor matrix of the projectile target, which is related to the shape, size, orientation, magnetic permeability and electrical conductivity of the target, and μ is the underwater magnetic permeability.

9. An underwater projectile position estimation system, comprising the underwater projectile velocity measurement system according to any one of claims 1 to 5, characterized in that: The position estimation system also includes a detection device 2 which is arranged perpendicularly to the detection device 1 and has an adjustable distance. The detection device 2 includes an excitation coil and at least one induction coil connected across the excitation coil. The central axis of the induction coil in the detection device 1 intersects perpendicularly with the central axis of the induction coil in the detection device 2.

10. A method for estimating the position of an underwater projectile, using the underwater projectile position estimation system according to claim 9, characterized in that: Methods include: According to the changes in the induced voltage amplitude at different vertical distances between the projectile and the induction coil, a database of the relationship between the induced voltage and the projectile coordinate position is established. The measured induced voltage is compared with the database to estimate the projectile position.

Images