Method for calculating armature exit velocity

Abstract

The method for calculating the muzzle velocity of an armature comprises the following steps: calculating the force F(t)=m(u(t),x(t))I of the armature 2 , wherein m(u(t),x(t)) is a thrust factor, and I is the amplitude of the exciting current of the power supply of the electromagnetic launching device; obtaining the motion state of the armature, including the real-time position of the armature at time t, the real-time velocity of the armature, and the real-time acceleration of the armature; updating the motion state of the armature; judging whether the armature has been launched according to the updated motion state of the armature, if yes, taking the real-time velocity of the armature at this time as the muzzle velocity of the armature, completing the calculation, otherwise, executing step S5; determining the instantaneous frequency of the exciting current of the power supply according to the real-time position of the armature, and returning to step S1. The skin depth is introduced when the force of the armature is calculated, so that the calculation is more in line with the actual situation, the change from the force of the armature changing with the position to the force of the armature changing with time is realized, the solution of the force of the armature is more accurate, and the accuracy of the muzzle velocity of the armature calculated based on the force is also higher.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electromagnetic launching, and particularly relates to a method for calculating the muzzle velocity of an armature in an electromagnetic rail launcher. BACKGROUND

[0002] The electromagnetic rail launcher is a device that uses a high-power power supply as an energy source and can efficiently convert high-power electric energy into kinetic energy in an instant. Compared with the gunpowder launching mode, the electromagnetic rail launching mode has the advantages of stable operation, good repeatability, accurate and adjustable thrust, short launching interval, etc., and thus has a wide application prospect in the field of anti- unmanned aerial vehicle cluster target air defense.

[0003] In the application process of the electromagnetic rail launcher, the outlet velocity of the projectile, that is, the muzzle velocity of the armature, needs to be calculated to understand the projectile motion characteristics of the electromagnetic rail launcher and provide a data basis for the rapid and accurate adjustment of the armature thrust. The traditional method for calculating the muzzle velocity of the armature is mainly to realize it by analyzing the conversion relationship between the power energy and the kinetic energy of the armature (Wang Ying, Xiao Feng. Electromagnetic gun principle [M]. National Defense Industry Press, 1995. 17-20). This is an approximate calculation method that uses the conversion relationship between the electric energy and the kinetic energy to approximately calculate the muzzle velocity of the armature. The calculation accuracy of this method depends on the accuracy of the inductance gradient of the electromagnetic rail launcher, and the inductance gradient is affected by factors such as the structure of the electromagnetic rail launcher and the frequency of the excitation current. Therefore, the inductance gradient varies greatly when different power supplies are used in different launchers, and thus it is difficult to accurately calculate and measure the inductance gradient. In addition, the inductance gradient changes with the frequency of the excitation current and the position of the armature, and when the muzzle velocity of the armature is approximately calculated by the conversion relationship between the electric energy and the kinetic energy, a fixed inductance gradient is used, which results in low calculation accuracy. In addition, the more complex the structure of the launcher, the more difficult it is to accurately obtain the inductance gradient, and this method is not suitable for calculating the muzzle velocity of the armature of a complex electromagnetic rail launcher such as an enhanced four-pole electromagnetic rail launcher.

[0004] Later, someone else proposed a finite element simulation method to determine the muzzle velocity of the armature. This method obtains the motion state of the armature through electromagnetic-structure coupling finite element simulation, but in actual application, due to the poor convergence of electromagnetic field finite element simulation in the motion state, the large grid scale caused by the large slenderness ratio of the electromagnetic rail launcher model in structure, and other reasons, the finite element simulation has high requirements on the computer performance, and usually requires hundreds of GB of memory to run for tens of hours to obtain the result. SUMMARY

[0005] The purpose of the present application is to provide a method for accurately calculating the muzzle velocity of the armature in the electromagnetic rail launcher, which provides a data basis for the accurate adjustment of the armature thrust.

[0006] In order to achieve the above object, the present application adopts the following technical solutions:

[0007] The application discloses a calculation method of armature muzzle velocity, which is used for calculating the muzzle velocity of an armature when the armature is launched by an electromagnetic track launching device, and the electromagnetic track launching device comprises a main track, an enhanced track arranged correspondingly to the main track, and an armature in contact with the main track.

[0008] S1, calculating the force F(t) of the armature;

[0009] F(t) = m(u(t), x(t))I 2 , wherein m(u(t), x(t)) is a thrust factor, I is the amplitude of the excitation current of the power supply of the electromagnetic launching device, μ0 is the vacuum permeability, u0 is the skin depth of the armature, r b is the width of the through-flow area of the armature, S k is the area of the region with the current density of the kth track, is a unit vector representing the direction of the magnetic field, r is the radius of the circular hole of the armature, l is the length of the through-flow area of the track, and x, y, z, u and v are all integral variables;

[0010] S2, obtaining the motion state of the armature, the motion state of the armature comprising the real-time position x t of the armature at the time t and the real-time velocity v t of the armature;

[0011] a t-1 is the real-time acceleration of the armature at the time t-1, v t-1 represents the real-time velocity of the armature at the time t-1, x t-1 represents the real-time position of the armature at the time t-1, Δt is the calculation step, a t-1 = (F(t)-f) / m, F(t) is the force of the armature, f is the friction between the armature and the main track, and m is the mass of the armature;

[0012] S3, updating the motion state of the armature according to the real-time position and the real-time velocity of the armature;

[0013] S4, judging whether the armature has been launched according to the updated motion state of the armature, if yes, taking the real-time velocity of the armature at this time as the muzzle velocity of the armature, and completing the calculation, or else executing step S5;

[0014] S5, determining the amplitude and the instantaneous frequency of the excitation current of the power supply according to the real-time position of the armature, and returning to step S1.

[0015] Further, according to the thrust factor formula, an armature thrust factor table reflecting the corresponding relationship between the instantaneous frequency of the excitation current, the real-time position of the armature and the thrust factor is established and stored, and in step S1, the thrust factor is determined by querying the armature thrust factor table according to the instantaneous frequency of the excitation current, the skin depth and the real-time position of the armature.

[0016] Further, in step S1, when the force of the armature is calculated for the first time, the instantaneous frequency of the excitation current is obtained by using the wavelet transform method to perform time-frequency analysis on the zero input response of the power supply at the initial moment.

[0017] It can be seen from the above technical solutions that the calculation method of the armature muzzle velocity of the present application is based on the calculation of the speed of the armature under force, and the skin depth is introduced in the calculation process to make the calculation closer to the actual situation. In the iterative calculation, the amplitude and instantaneous frequency of the excitation current of the power supply are determined according to the updated motion state of the armature, the transition from the change of armature force with position to the change of armature force with time is realized, the solution of the force is more accurate, and the accuracy of the final muzzle velocity calculation result is improved. By introducing the thrust factor, the calculation formula of the force of the armature is simplified, and the calculation amount is reduced. In the preferred technical solution, the armature thrust factor table is established in advance, and the thrust factor results related to the instantaneous frequency of the excitation current, the skin depth and the real-time position of the armature are stored in advance. The thrust factor is determined by looking up the table during calculation, which greatly reduces the calculation amount of the iterative calculation and shortens the calculation time. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creating laborious work.

[0019] Figure 1 Fig. 1 is a schematic diagram of the track and armature of a four-pole electromagnetic track launcher;

[0020] Figure 2 Fig. 2 is a flowchart of the method of the present application;

[0021] Figure 3 Fig. 3 is a simulation diagram of the current density distribution of the track of the electromagnetic launcher;

[0022] Figure 4 Fig. 4 is a schematic diagram of the area with current density and the area with zero current density of the track of the electromagnetic launcher;

[0023] Figure 5 Fig. 5 is a schematic diagram of the area of the cross section of the track;

[0024] Figure 6 Circuit diagram of type I PFN.

[0025] The specific embodiments of the present application are further described in detail below with reference to the accompanying drawings. DETAILED DESCRIPTION

[0026] The present application will be described in detail below with reference to the accompanying drawings. In describing the embodiments of the present application, the drawings may be partially enlarged without the general scale for the purpose of illustration, and the schematic diagrams are only examples which should not limit the scope of the present application. It should be noted that the drawings are simplified and all use non-precise scales, only for the purpose of facilitating and clearly assisting the description of the embodiments of the present application. Meanwhile, in the description of the present application, the terms “first”, “second” and the like are only used for distinguishing description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features; the terms “positive”, “negative”, “bottom”, “upper”, “lower” and the like indicate the orientation or positional relationship shown in the drawings, only for the purpose of facilitating the description of the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0027] The electromagnetic rail launcher is generally powered by a pulse power supply, and the capacitor energy storage type pulse power supply composed of a pulse forming network (PFN) has the advantages of flexible and convenient current and voltage waveform adjustment capability, and is widely used in electromagnetic rail launchers. The electromagnetic rail launcher mainly includes a rail and an armature. Figure 1It is a structural schematic diagram of an enhanced quadrupole electromagnetic rail launcher, the quadrupole electromagnetic rail launcher has four main rails, and the enhanced quadrupole electromagnetic rail launcher has four enhanced rails 101 in addition to the four main rails 100, the enhanced rails 101 and the main rails 100 are arranged one by one, that is, one main rail 100 corresponds to one enhanced rail 101 arranged outside. The four main rails 100 are arranged in a 90° array and symmetrically located around the armature 102. The four main rails 100 can form a symmetrical magnetic field, thereby ensuring that the electromagnetic rail launcher is uniformly stressed. The currents on the two main rails 100 opposite to each other in the quadrupole electromagnetic rail launcher are equal in size and the same in direction, the currents on the two adjacent main rails 100 are opposite in direction, and the current on the main rail 100 is the same in direction as the current on the corresponding enhanced rail 101. The (quadrupole) armature 102 is arranged between the main rails 100 and is in contact with the main rails 100 through flexible armature arms, and the armature arms and the main rails 100 are in interference fit. The quadrupole armature is an armature with four armature arms, each armature arm is in contact with one main rail, and the structure of the quadrupole armature can refer to the structure of the armature disclosed in Chinese Invention Patent No. 201910097540.9.

[0028] As shown in Figure 2 The steps of the armature muzzle velocity calculation method of the application are as follows:

[0029] S1, calculate the force of the armature; the force of the armature calculated in this step refers to the thrust received by the armature during the launching process;

[0030] The thrust F received by the armature during the launching process is related to the (real-time) position of the armature and the instantaneous frequency of the excitation current of the power supply, according to the Biot-Savart law, the thrust In the formula, J A is the current density of the armature, B k is the magnetic field excited by the kth rail, n is the number of rails, for the enhanced quadrupole rail launcher, the number of rails n is 8, V is the through-flow area of the rail, the length l of the through-flow area changes with the movement time of the armature; the through-flow area is a region with a relatively large current density in the conductor, the current in the conductor follows Ampere's law, the smaller the resistance, the larger the current density, in addition, the distribution of the current density is also affected by the skin effect, in the present application, the through-flow areas of different conductors (rails, armatures) are different, the through-flow area of the rail is the area extending inward from the surface of the rail to the skin depth, but the lengths of the through-flow areas of the main rail and the enhanced rail are different, for the enhanced rail, the through-flow area is equal in length to the enhanced rail, that is, l is the length of the enhanced rail, for the main rail, the through-flow area is the area between the head of the armature and the breech, as shown in Figure 1The length of the through-flow region is the distance between the end face of the armature head and the breech. The breech and the muzzle are the two opposite ends of the electromagnetic rail launcher. The armature is loaded into the electromagnetic rail launcher from the breech and is launched from the electromagnetic rail launcher from the muzzle. That is, the muzzle is the end in the direction of the movement of the armature, and the breech is the end away from the direction of the movement of the armature.

[0031] The magnetic field excited by the kth rail In the formula, μ0 is the magnetic permeability in vacuum, J R(k) is the current density of the kth rail, r is the radius of the armature hole, is the unit vector representing the direction of the magnetic field, J R(k) = I / S k , I is the amplitude of the excitation current, According to the right-hand rule, l is the length of the rail through-flow region, x, y, z, u, v are all integral variables, x, y, z are the coordinates of a certain point in space, u, v are the coordinates of a certain point on the rail cross section (xoy plane), V is the region of triple integration of x, y, z, V is also the armature region, S is the region of double integration of variables u, v, as shown in Figure 3 , S includes the region enclosed by the outer contour lines (l1, l2, l3, l4, l7) of the main rail and the region enclosed by the outer contour lines (l5, l6, l8, l9) of the enhanced rail, and the curve equations of l1, l2, l3, l4, l5, l6 are as follows:

[0032] In the formula, w is the length of the cross section of the enhanced rail, h is the height of the cross section of the main rail, and b is the farthest distance between the two opposite surfaces of the armature in contact with the main rail. The armature has a total of 4 surfaces in contact with the main rail, and the two opposite surfaces are opposite to each other. The farthest distance between the two opposite surfaces is b.

[0033] Figure 4 is the simulation diagram of the current density distribution of the main rail and the enhanced rail, from Figure 4 It can be seen that not all regions in the main rail 100 and the enhanced rail 101 have current density. For example, the peripheral region of the enhanced rail 101 has current density, and the current density of the middle region is zero. In the main rail 100, the peripheral region of the main rail 100 opposite to the enhanced rail 101 has current density, and the current density of the remaining region is zero. That is, the region with current density in the main rail 100 and the enhanced rail 101 is Figure 4The area of the region with current density (the hatched region) is related to the skin depth, which refers to the thickness in which most of the charge is located when the charge propagates in the conductor. In this embodiment, for the main track, the area of the region with current density S k = 4.86u1 2 + 154u1+2704, u1 is the skin depth of the main track; for the enhancement track, the area of the region with current density S k = -4u2 2 + 64u2, u2 is the skin depth of the enhancement track; the skin depth u can be calculated by the following formula: In the formula, μ0 is the magnetic permeability in vacuum, is the instantaneous frequency of the excitation current, and σ is the conductivity of the (track / armature) material;

[0034] If the force on the armature is calculated according to the above formula, multiple integrations and accumulations are required, which is time-consuming and computationally intensive. However, as can be seen from the above formula, the thrust on the armature during the emission process is related to the amplitude, instantaneous frequency of the excitation current, and armature position. The relationship between the instantaneous frequency of the excitation current and the force on the armature is relatively complex. Therefore, in order to facilitate calculation, the amplitude I of the excitation current is separated out, and the instantaneous frequency of the excitation current and the real-time position of the armature are used as two parameters to define a thrust factor, denoted as m(u(t), x(t)), and the thrust on the armature during the emission process is F(t) = m(u(t), x(t))I 2 , which simplifies the calculation;

[0035] Thrust factor S k is the area of the region with current density of the kth track, u0 is the skin depth of the armature, and r b is the width of the armature current-carrying region. The width of the armature current-carrying region of the present application extends inward from the outer surface of the armature by 1 / 4 of the armature aperture, and the length of the armature current-carrying region extends from the throat 102b to the head 102a of the armature by the skin depth Figure 1 . As shown in the figure, the width of the armature current-carrying region of the present embodiment is Figure 3 . The cross-sectional shape of the surface where the armature (arm) and the main track are in contact is arc-shaped, and R is the radius of the arc, I / (2u0r b , i.e. the current density of the armature;

[0036] As can be seen from the thrust factor formula, the thrust factor is related to the skin depth and the real-time position of the armature, and changes with time t. The real-time position of the armature refers to the distance between the armature and the breech at time t, while the skin depth is related to the instantaneous frequency of the excitation current. To improve the calculation speed, this invention establishes an armature thrust factor table based on the thrust factor formula and the correspondence between the thrust factor, the instantaneous frequency of the excitation current, and the real-time position of the armature. By pre-solving the thrust factor under different parameters (instantaneous frequency of the excitation current, skin depth, and real-time position of the armature) and storing it in a table, the integration and accumulation steps in the armature force calculation process are omitted, thereby improving the calculation speed. After establishing the armature thrust factor table, knowing the instantaneous frequency of the excitation current, the skin depth, and the armature position, the thrust factor can be determined by querying the armature thrust factor table, and then... The forces acting on the armature can be quickly calculated. The armature thrust factor is shown in Table 1. Due to space limitations, Table 1 shows some armature thrust factor values ​​corresponding to the instantaneous frequency of the excitation current, the skin depth, and the armature position.

[0037] Table 1

[0038]

[0039] After determining the instantaneous frequency of the excitation current, the skin depth, and the real-time position of the armature at time t, the thrust factor m(u(t),x(t)) can be determined by looking up a table, and then the formula F(t)=m(u(t),x(t))I can be used. 2 The thrust on the armature is calculated. In the initial calculation, the instantaneous frequency of the excitation current can be obtained by performing time-frequency analysis on the zero-input response of the power supply at the initial moment using the wavelet transform method. The use of the wavelet transform method for time-frequency analysis is a known method and is not an innovation of this invention, so it will not be elaborated here. Theoretically, the amplitude of the excitation current is 0. In order to give the armature an initial acceleration, this invention will preset an initial value of the excitation current. The initial value of the excitation current is generally relatively small, such as 1A.

[0040] S2. Obtain the motion state of the armature, which refers to the real-time position x of the armature at time t. t and the real-time speed v of the armature t ;

[0041] a in the formula t-1 Let v be the real-time acceleration of the armature at time t-1. t-1 x represents the real-time velocity of the armature at time t-1. t-1 This represents the real-time position of the armature at time t-1, where Δt is the calculation step size; a t-1=(F(t)-f) / m, F(t) is the force of the armature, f is the friction between the armature and the main track, m is the mass of the armature, the calculation step is an empirical value, the smaller the step, the higher the calculation accuracy, but the more iterations, the longest time, to ensure accuracy, the maximum calculation step should not exceed 1% of the estimated armature ejection time, the calculation step in this embodiment is 0.001 ms;

[0042] In the first iteration calculation, the motion state of the armature refers to the initial position and initial speed of the armature, both of which are known, and in subsequent iteration calculations, the motion state of the armature will be updated;

[0043] The initial position of the armature can be any position inside the launcher, and there is no specific requirement, but generally, according to the 2 times caliber rule, the armature is usually installed at a position 2 times the armature caliber length away from the breech, and the initial speed and initial acceleration of the armature are usually 0; but some current research suggests that providing an initial speed to the armature can help improve the efficiency of the electromagnetic launcher, so an initial speed can also be given to the armature, which is known;

[0044] S3, updating the motion state of the armature according to the real-time position and real-time speed of the armature obtained in step S2;

[0045] S4, determining whether the armature has been ejected according to the updated motion state of the armature, that is, the real-time position of the armature obtained in step S2, if so, taking the real-time speed of the armature at this time as the ejection speed of the armature, completing the calculation, otherwise executing step S5;

[0046] S5, determining the amplitude and instantaneous frequency of the excitation current of the power supply according to the real-time position of the armature, and returning to step S1.

[0047] The Simulink tool in matlab software can be used to build a power supply circuit to obtain the amplitude of the excitation current, and after obtaining the amplitude of the excitation current, time-frequency analysis tool can be used to obtain the instantaneous frequency of the excitation current. This method is a known method, and specific reference can be made to Hou Junchao's research on electromagnetic field and electromagnetic force dynamic characteristics of electromagnetic track launchers, which will not be repeated here.

[0048] Alternatively, the amplitude of the excitation current can be calculated by solving the differential equation of the power supply circuit, and then the amplitude of the excitation current can be analyzed to obtain the instantaneous frequency of the excitation current.

[0049] Figure 6 The circuit diagram of I-type PFN is shown in the figure, for the capacitor energy storage type pulse power supply composed of PFN, according to the conduction state of the freewheeling branch D, the discharge process of the pulse capacitor is divided into two stages, as shown in Figure 6the first stage shown in the middle part of a and Figure 6 the second stage shown in the middle part of b. Before the PFN works, the capacitor is charged. When the PFN starts to work, the capacitor discharges, the freewheeling branch D is off (not conducting), as shown in the middle part of a. Figure 6 During the working process of the PFN, the armature moves and consumes electric energy, the voltage of the capacitor decreases, the freewheeling branch D is on, and the second stage shown in the middle part of b is entered. Figure 6 During the working process of the PFN, the armature moves and consumes electric energy, the voltage of the capacitor decreases, the freewheeling branch D is on, and the second stage shown in the middle part of b is entered. Figure 6 The part in the middle dotted line box is the capacitor branch, the part in the dashed line is the freewheeling branch, and the armature and the track are the load in the electromagnetic track launcher.

[0050] The response equation of the first stage is:

[0051] The response equation of the second stage is: In the formula, U0 is the charging voltage of the capacitor, L c is the stray inductance of the capacitor branch, L R is the inductance of the armature and the track (load), e is the natural constant, I0 is the current amplitude of the load branch when the PFN is switched from the first stage to the second stage, R R is the resistance of the armature and the track (load), a = (R C + R D ) / 2 (L C + L D ), R c is the internal resistance of the capacitor branch, R D is the stray resistance of the freewheeling branch, L D is the stray inductance of the freewheeling branch, R R = R R0 + R'x, L R = L R0 + 2m(u(t), x(t)), x represents the displacement of the armature, that is, the real-time position of the armature, R' is the resistance gradient of the load, R R0 is the resistance of the load when the displacement of the armature is zero, L R0 is the inductance of the load when the displacement of the armature is zero.

[0052] The above calculation formula is based on the pulse shaping network shown in Figure 6 , to calculate the current. When the specific form of the pulse shaping network is different, the calculation formula of the current amplitude will be different. The differential calculation equation of the current amplitude of other pulse shaping networks can refer to the book Electromagnetic Track Launching Theory and Technology by Lu Junyong and Ma Weiming. Here, no further description is given.

[0053] Compared with the method of finite element simulation, the method of the application can greatly shorten the calculation time and reduce resource consumption, because the finite element simulation often needs to consume hundreds of GB of memory and tens of hours of time when calculating the electro-magnetic-motion coupling, while the method of the application adopts the look-up table calculation method when calculating the stress of the armature, and part of the data has been stored in advance. Compared with the calculation method of electric energy and kinetic energy conversion, the calculation method of electric energy and kinetic energy conversion is to solve the PFN circuit of fixed load or solve the PFN circuit after the change rule of the load is given, and the resistance and inductance (R R 、L R ) of the armature and the track are approximated by an empirical value (constant) during the launching process, without considering the changes of the two in the launching process with the position of the armature, while the method of the application more accurately simulates the current distribution in the armature and the track of the launcher through time-frequency analysis and research on the skin effect, and calculates the circuit load (R R 、L R ) according to the movement of the armature (the real-time position of the armature), so that the calculation accuracy can be effectively improved.

[0054] In order to verify the effect of the method of the application, the method of the application and the finite element simulation method are used to calculate the muzzle velocity of the armature. The structure of the electromagnetic launcher is shown in Figure 1 , and the simulation parameters are shown in Table 2. When the body current and surface current method is used to calculate the stress, the amplitude of the excitation current is 35 kA, and the instantaneous frequency of the excitation current is 3700 Hz. The results are shown in Table 3.

[0055] Table 2 Simulation parameter table

[0056]

[0057] Table 3

[0058]

[0059] The bulk current and the surface current in Table 3 are the calculation methods of armature stress given in "Mechanical Analysis of Electromagnetic Rail Launcher Assembly [M], Bai Xiangzhong, Zhao Jianbo, Tian Zhenguo, National Defense Industry Press, P28". The two calculation methods simplify the current distribution in the rail as uniform distribution in the rail and only surface distribution in the rail respectively when calculating the stress of the armature by using the Biot-Savart law. It can be seen from the above results that the calculation result of the method of the application is closer to the result of the finite element simulation than the bulk current and the surface current method, because the method of the application changes the simulation method of the current distribution in the rail, considers that the current is distributed in the skin depth of the rail, introduces the skin depth parameter, is closer to the real situation, and can realize the change from the armature stress changing with the position to the armature stress changing with time when calculating the stress of the armature according to the updated armature motion state to determine the amplitude and instantaneous frequency of the excitation current of the power supply, so the solution of the stress is more accurate. At the same time, the method of the application also introduces the thrust factor, establishes the armature thrust factor table, stores the thrust factor results related to the instantaneous frequency of the excitation current, the skin depth and the real-time position of the armature in advance, and simplifies the calculation formula of the armature stress, so compared with the finite element simulation method, the calculation amount of iterative calculation is greatly reduced, and the calculation time is shortened.

[0060] The above is only the preferred embodiment of the application, and does not limit the application in any form. Although the application has been disclosed as above, it is not intended to limit the application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content without departing from the scope of the technical solution of the application, and any simple modification, equivalent change and modification of the above embodiments according to the technical essence of the application are still within the scope of the technical solution of the application.

Claims

1. A method of calculating muzzle velocity of an armature, for calculating the muzzle velocity of an armature when the armature is launched by an electromagnetic rail launcher, the electromagnetic rail launcher comprising a main rail, an enhanced rail provided in correspondence with the main rail, and an armature in contact with the main rail, characterized in that, The method comprises the following steps: S1, calculating the force F(t) of the armature; F(t) = m(u(t), x(t)) I 2 where m(u(t), x(t)) is a thrust factor and I is an amplitude of an exciting current of a power supply of the electromagnetic launcher, where μ0is a vacuum permeability, u0is a skin depth of the armature, r b is a width of the armature through-flow area, S k is an area of the kth track with a current density, is a unit vector indicating a direction of a magnetic field, r is a radius of the armature circular hole, l is a length of the track through-flow area, x, y, z, u, v are all integral variables; S2, acquiring the motion state of the armature, the motion state of the armature including the real-time position x of the armature at time t t and the real-time speed v of the armature t ; a in the formula t-1 is the real-time acceleration of the armature at time t-1, v t-1 represents the real-time speed of the armature at time t-1, x t-1 represents the real-time position of the armature at time t-1, Δt is the calculation step, a t-1 = (F(t) - f) / m, F(t) is the force of the armature, f is the friction between the armature and the main track, and m is the mass of the armature S3, updating the motion state of the armature according to the real-time position and real-time speed of the armature; S4, judging whether the armature has been ejected according to the updated motion state of the armature, if yes, taking the real-time speed of the armature at this time as the ejection speed of the armature, completing the calculation, otherwise executing step S5; S5, determining the amplitude and instantaneous frequency of the exciting current of the power supply according to the real-time position of the armature, and returning to step S1.

2. The method of calculating muzzle velocity of an armature of claim 1, wherein: According to the thrust factor formula, an armature thrust factor table reflecting the corresponding relationship between the thrust factor and the instantaneous frequency of the exciting current, the real-time position of the armature is established and stored, and in step S1, the thrust factor is determined by querying the armature thrust factor table according to the instantaneous frequency of the exciting current, the skin depth and the real-time position of the armature.

3. The method of calculating muzzle velocity of an armature of claim 1, wherein: In step S1, when the force of the armature is calculated for the first time, the instantaneous frequency of the exciting current adopts the wavelet transform method, and the time-frequency analysis of the zero input response of the power supply at the initial moment is obtained.

Images