Railgun Research Articles

2-D Topology Optimization of the Breech Flat-Plate Bus Bar of the Electromagnetic Railgun

The optimization of the breech bus bar has an important influence on the lightweight research of the electromagnetic railgun. A topology optimization model considering volume constraints is established for the breech flat-plate bus bar. The bus bar is fed through sixteen coaxial cables. The optimal structure of the bus bar is calculated and given under the requirement of 50% volume constraint. In addition, the influence of four control parameters is also analyzed. These four parameters are respectively the prescribed volume fraction, the positioning dimension of cable arrangement, the filter radius, and the penalization power. For the first parameter, the optimal structures of the bus bar are given and compared when it is respectively 0.4, 0.6, 0.7, and 0.8. For the second parameter, the results show that the larger the positioning dimension, the smaller the size of all parts of the bus bar. For the third parameter, it is suggested to use the surrounding two-layer elements of each element to conduct sensitivity filtering. For the fourth parameter, it is reasonable to choose 3.0 as the penalization power value. It is meaningful for the structural design of the bus bar in the initial design stage.

Optimization of Electromagnetic Railgun and Projectile’s Trajectory by Genetic Algorithm

In this paper, the optimization of the electromagnetic railgun and its projectile path is proposed. The circuit model is used to optimize and simulate the elec- tromagnetic railgun, in which the equivalent circuit of the railgun is extracted. Then the differential equations expressing the physics governing the system are obtained. Using the projectile path equations and simulating them in MATLAB, the output of the simulation of the electromagnetic railgun and its projectile path in MATLAB software has been analyzed. The main advantage of the models used is that they can be used in matters of sensitivity and optimization due to their high speed. Based on the obtained outputs of electromagnetic railgun and projectile path, the cost function is presented, and then the effective parameters of models are optimized using the genetic algorithm. The results show that the losses and costs are drastically reduced for the same purposes, and the waste of costs and energy is prevented.

System Noise Suppression of Muzzle Voltage in Augmented Electromagnetic Railgun Based on VMD and the Application in Armature–Rail Contact Characteristics

The muzzle voltage is an important characteristic parameter of electromagnetic railgun. The contact resistance between the sliding armature and the copper rail surface during the launching process can be calculated by utilizing it to analyze the armature–rail contact characteristics. However, in the engineering experiments of augmented electromagnetic railgun, the detected muzzle voltage waveform will be disturbed by the system noise because of the existence of augmented rail, firing sequence of pulse forming network (PFN), and friction of armature–rail contact surface. Therefore, it is difficult to calculate the contact resistance accurately. This article presents a new noise suppression method variational mode decomposition (VMD) for suppressing the jagged noise in the muzzle voltage. A method for calculating the contact resistance is presented to analyze the armature–rail contact characteristics. A frame for analyzing the contact characteristics of the electromagnetic railgun is presented. The method can suppress the system noise by utilizing the signal mode decomposition in the time domain based on the frequency characteristics of VMD. Then, in order to analyze the armature–rail contact characteristics, the contact resistance can be calculated according to the formula derived from the theory. The results show that the method can suppress the muzzle voltage system noise effectively. And the calculated contact resistance wave is smooth, which is helpful to analyze the armature–rail contact characteristics. The noise component extracted from muzzle voltage contains pulse signals, and the time and amplitude of these pulse signals are related to PFN’s firing sequence and the changing trend of the armature–rail contact resistance. The method proposed in this article provides a new and reliable reference for monitoring the launching state of electromagnetic railgun in engineering experiments.

Design of Analog Electromagnetic Gun Based on Arduino

Design of Analog Electromagnetic Gun Based on Arduino

Finite Element-Boundary Element Method Based Simulations of Electromagnetic Railgun in Augmented Configurations

When dealing with electromechanical system modelling, numerical challenges are inevitable. Especially when working with moving conductor problems, such as rotational or linear motors, special care needs to be taken for the air-gap region. Railguns air region is one more addition to this modelling problem. The air region necessitates either remeshing or a custom mesh topology. In addition, the production of air mesh for conductors with complicated shapes has its own difficulties. The air mesh requirement may be reduced by using the finite element-boundary element (FE-BE) technique. Boundary elements for air mesh and finite elements for conductors allow for the creation of models with moving conductors and makes model production easier and quicker. This paper investigates the changes observed in the railgun's electrical and mechanical parameters through the finite element-boundary element simulation approach when the geometry of the augmentation rails in a railgun is changed. Tapering and filleting are two geometry changes implemented on the augmenting rails of an electromagnetic railgun. Designed railgun variants are investigated using LS-Dyna software. A new formulation for breech voltage in augmented electromagnetic railguns is derived to calculate barrel efficiency. Four configurations of augmented electromagnetic railguns are analyzed, emphasizing force profile, inductance gradient, and motional-emf ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$iL^{\prime }v$</tex-math></inline-formula> ). One of the new configurations has resulted in an improvement in the force profile during the initial stages of the launch by 8.8%, and the armature's final muzzle velocity has improved by 7%.

Study on Wear of Electromagnetic Railgun

Sliding friction wear of high-speed current-carrying is a key factor limiting the engineering of electromagnetic railgun, and is also a hot spot and difficult area for current research. In this paper, we simulate the internal ballistic dynamics and electrical contact characteristics based on multi-physics field effects and consider the actual working conditions such as Lorentz force, friction force and interference fit to simulate the motion of the armature in the bore. Based on the Archard wear model, a finite element simulation method combining HyperMesh and ANSYS is proposed to realize the wear prediction. The simulation results are compared with the experimental results to verify the accuracy of the prediction model. The results show that under the single firing condition, the wear is mainly concentrated at the end of the armature arm, and the rail wear is relatively light; with the increase of electromagnetic thrust, the increase of armature wear volume does not change much and is approximately equal; the armature wear volume is influenced by the wear coefficient, in which the armature wear volume increases about 190 times when the wear coefficient increases from 1×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-6</sup> to 1×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> . Therefore, in order to reduce the degree of wear between the armature and rails, the lubrication conditions should be improved as much as possible. This study provides a simulation method for the wear prediction of electromagnetic rail launcher, which is important for the engineering application of electromagnetic rail launcher.

Material Characterization of Follower Assembly of G5 155mm Gun Howitzer Breach Mechanism Block

Medium alloy steel is widely used as a material for guns and rocket launchers due to its high strength and excellent machinability characteristics. The purpose of this study is to determine the material properties of the follower assembly used in a breech block gun launcher which is significantly important f or t he future product improvement. The microstructure and the effect of alloying elements in the follower assembly is evaluated in this study. The SPECTRO Optical Emission Spectroscopy (ES) method is used to analyse the chemical composition of the material and the Field Emission Scanning Electron Microscope coupled with Energy Dispersive X-Ray (FESEM-EDX) were used to analyse the inclusions of the sample. Results of the ES chemical composition analysis found that Nickel (Ni) is the major alloying elements beside Molybdenum (Mo), Chromium (Cr), Manganese (Mn), Silicon (Si), Sulphur (S), and Carbon (C) while chemical mapping and line scanning analysis of FESEM-EDX on inclusions distributed in the material microstructure identified as a compound of Manganese Sulphur(MnS). Fine dendritic microstructure arrangement and distribution in the microstructure analysis showed that the sample had been quenching in the heat treatment process, which also played a significant role in the material characterization. From the analysis, it is found that the material can be defined as medium alloy steel that is also typical for high strength material for ballistic application.

A Calibration Method of Inner Bore Profile Detecting on Electromagnetic Railgun

When the electromagnetic rail gun accelerates the armature, the rail is in a harsh condition of high temperature, high pressure and powerful current which will cause a series of grooving phenomenon. In order to detect the inner bore profile, we developed a measuring device using laser triangulation method and basically realized the measurement of the inner bore profile measurement. However, except for the translation and deflection errors, we found that the actual measurement cross-section would be rotated due to the unsteady movement compared with the ideal section. In addition, the previous calibration needs a high-resolution image sensor to get deflection information, it means high cost. In this paper, we analyzed the 3 kinds of deviations and provide a method to calibrate the rotation error using a calibration block. An improved calibration system was designed in low cost and experiment verified the feasibility of the calibration method. The calibration system can be divided into 3 parts, the outside global laser light provides a constant central position, a distance detecting device with a cone laser generator and an inside calibration block. After experiment, the calibration method was effective and the deviation of the profile can be corrected.

Study on Effect of Rail Filet Radius in Electromagnetic Railgun

Enhancing the inductance gradient of an electromagnetic railgun (EMRG) directly translates to an improvement in the force on the projectile. Fileting the rails on one side is one of the ways to improve the inductance gradient. This work focuses on the effects of filet arc radius on different parameters of inductance gradient, current density distribution, magnetic flux density, barrel efficiency, breech energy, and critical velocity. The performance of rails with filet arc radius of 2, 4, and 6 mm are compared with the conventional cuboid shape rail geometry. Dynamic field distributions are analyzed by simulating the designed systems in LS-DYNA. A magneto-static analysis is performed using Ansys-Maxwell to determine the magnetic flux density produced behind the armature. It is observed that there is an increase in the flux density and barrel efficiency when filet radius increases. An improvement of 3.81% is observed in the flux density and the barrel efficiency improved from 24% in conventional rails to 27% in rails with a filet radius of 6 mm.

Structural Design Optimization and Prestress Simulation of the Laminate-Containment Launcher

The laminate-containment launcher is a high-efficiency electromagnetic railgun launcher (EMRL), which uses a laminate structure to reduce eddy current loss. However, the research on the design optimization of the laminate-containment launcher with prestress and mass as the goal is rarely mentioned. In this article, some key parameters of the laminate-containment launcher—the magnitude of interference $s$ , the axial thickness of the steel laminate $t_{s}$ and insulation laminate $t_{i}$ , the thickness of inner glass fiber $r_{g}$ , and the radial thickness of the laminate $r_{l}$ —are studied. On this basis, the influence of the five parameters on the hoop stress of the rail is fitted as a function by using the multiple nonlinear regression method. Then, the maximum hoop stress $f_{\mathrm {1max}}$ and the maximum hoop stress difference $f_{\mathrm {2max}}$ of the rail are calculated by using a nonlinear programming algorithm. Finally, the maximum hoop stress $f_{\mathrm {1max}}$ , the maximum hoop stress difference $f_{\mathrm {2max}}$ , and the maximum mass $f_{\mathrm {3max}}$ are taken as the reference values, and the optimal solution of the multiobjective function is obtained by using the weighted nonlinear programming algorithm. The results can be described as follows: the hoop stress of the rail changes linearly with the increase of the magnitude of interference, while the hoop stress changes approximately quadratic with the change of other parameters. Through the optimization of nonlinear programming algorithm with weighted form, the optimal design under different weighted values is obtained, which has a small error compared with the calculation results of ANSYS. The important characteristic that the hoop stress of the laminate-containment launcher presents wavy variation along the axial direction is obtained by numerical simulation. These results can provide theoretical guidance for the structural design of the laminate-containment launcher.

A Novel Hybrid Energy Storage System for Large Shipborne Electromagnetic Railgun

Although the pulsed power supply (PPS) based on capacitor has been successfully applied to engineering prototype of electromagnetic (EM) railgun, its large volume makes it poor adaptability and flexibility due to relatively low energy storage density. In this article, a novel hybrid energy storage system based on battery and pulsed alternator is proposed. The topology principle of the system, the design scheme of the pulsed alternator, and the cosimulation results of multimodules are described in detail. The research results show that the proposed system can be used as the driving power of EM railgun with 40 MJ muzzle kinetic energy, and the effective energy storage density (energy released in a single pulse) of the pulsed alternator can reach 6.3 MJ/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . Taking into account the charging motors, converter thyristors, and other auxiliary components, the effective energy storage density of PPS system will be 3 MJ/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> and the overall volume can be reduced to one-third of the current capacitive PPS.

Optimization Design of a 40-kJ HTSPPT Module for Inductive Pulsed Power Supply

The topology category based on high-temperature superconducting pulse power transformer (HTSPPT) is an important branch of inductive pulse power supply (IPPS) for rail guns. Optimization design of the HTSPPT can improve the overall performance of the IPPS system. The purpose of this article is to design a 40-kJ air-core HTSPPT module with a high-temperature superconducting (HTS) primary winding and a normally conducting secondary winding. According to the application characteristics of the HTSPPT, under the constraints of the three main performance indicators of critical current, stored energy, and coupling coefficient, the amount of HTS tapes and the volume of the entire HTSPPT are reduced as much as possible. The design of the secondary winding combines the electromagnetic launch requirements for the current pulse in the approximate flat waveform and steep pulse rising edge. With this optimized design, a 43-kJ HTSPPT module with a primary inductance of 79.4 mH, a secondary inductance of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$255.4~\mu \text{H}$ </tex-math></inline-formula> , and a coupling coefficient of 0.97 was obtained. Finally, the maximum stress and strain of the designed HTSPPT in the energy storage state are analyzed through the electromagnetic (EM) structure coupling field.

Analysis about Change of the Armature's Average Speed for an Experimental Rail Launcher

In this paper, we measured the armature velocity of an experimental electromagnetic launcher by B‐dot method and analyzed the change of the armature's average speed. The electromagnetic gun launching process was also simulated by Ansoft Maxwell simulation software. The launch current is used as the model's excitation which means that the current in the model is the same as the rail current. Ansoft Maxwell's 3D model can accurately simulate the launching process, in theory. We found that there was an unexpected rise during the real launching process. The phenomenon can be discovered in the following several experiments. We analyzed several possible causes such as the inductive gradient change, rail broken and inaccurate measurement of B‐dot probe. The inductive gradient is an important parameter in the launching process and can affect the armature speed. After checking the measurement problem, we also found that the wave form of the output signal from the probe where the unexpected change occurred was normal but the amplitude was very small. The measurement method was proved correct. The rise of average inductance gradient leads to the unexpected increase in average speed and the small signal. Furthermore, the physical reason for the change of inductance gradient should be the change of current distribution. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Research on impact resistance of ceramic matrix composites

The honeycomb structure has been used in the field of bulletproof materials, but there is little research on the impact resistance of ceramic honeycomb materials. In this res earch, ceramic matrix composite plates were prepared by using square-hole honeycomb ceramics and filling the honeycomb structure with second-phase reinforcing materials. Using LS-DYNA software to carry out numerical simulation analysis of the two groups of impact processes, to investigate the improvement effect of the composite material compared with the impact resistance of the honeycomb ceramic material, and at the same time, the 7.62 mm ballistic gun launcher was used to test the impact of composite plate and ceramic matrix on the honeycomb ceramic control target. The results show that the honeycomb ceramic material will break prematurely when it is impacted by the projectile at high speed, and the impact resistance is poor. The toughness of ceramic matrix composites filled with reinforcing materials is enhanced. Compared with honeycomb ceramic materials, the energy absorption efficiency of the composite material under the same thickness is increased by 115.6%, and the energy absorption density is increased by 52.3%, which improves the poor brittleness of ceramic materials.

Analysis and Preliminary Experimental Research of a Multiphase Air-Core Pulsed Alternator

The air-core pulsed alternator capable of miniaturization and lightweight has become one of the most potential power supplies for electromagnetic railguns equipped in all-electric vehicles or ships that have strict restrictions on volume and weight. Although the air-core machine has undergone decades of continuous research, a systematic theoretical basis is still in absence, especially for electromagnetic analysis and transient operating analysis. Besides, researchers are less willing to share their latest achievements for the sake of national interests, and the detailed experimental results of this alternator are seldom made public in recent years. In this article, the electromagnetic theoretical analysis, including the analytical expressions of magnetic flux density and inductance parameters, is carried out. Then, a comprehensive transient operating theoretical analysis of four stages is put forward with some typical operating parameters derived. Based on these two kinds of theoretical analysis, the scheme of a six-pole and seven-phase alternator is determined. Simulations are executed to verify the theoretical analysis and prove that the designed alternator can meet the proposed operating targets. Finally, some preliminary experiments for the fabricated prototype are conducted under low experimental parameters. The experimental results indicate that the power electronic devices can work properly, and the self-excitation rectifier takes effect in lifting up the field current. Although the discharge experiment is not carried out under rated experimental parameters, it still makes sense since it reveals the superiority of the prototype in releasing a discharge current very close to an ideal trapezoidal wave to ensure that the projectile can move steadily in its acceleration process.

Aerodynamic Performance Enhancement of Electromagnetic Gun Projectile Using Numerical Techniques

The unique study named aerodynamic performance enhancement of electromagnetic (EM) gun Projectile using numerical techniques is adopted to determine the better understanding of its aerodynamic characteristics. The earlier studies on EM gun projectile could explore its aerodynamic stability during flight whereas this unique research explains the enhancement of aerodynamic performance of EM gun projectile using numerical techniques. By using the Navier-Stokes numerical approach for a steady-state compressible flow, the Computational Fluid Dynamics (CFD) simulation of density, pressure, and temperature flow contours of the EM gun projectile flow field at different Mach number- 5 to 10 with an increment of 0.5 at zero angle of attack (AOA) have been analyzed. The results show an excellent agreement for the Mach numbers 5, 6, and 7. Moreover, to ensure accurate knowledge of the aerodynamic performance of EM gun projectile the numerical test is conducted several times using different turbulence models and differing the grid element sizes for Mach number 7. The results prove that at hypersonic speed the EM gun projectile performs in a much better way at Mach number 7. This best performance is analyzed by using the Spalart Allmaras (SA) turbulence model for grid size 5.4169e-03m. This work will help the researchers to do further improvements in EM gun projectile aerodynamic behaviors and also can be useful for military purposes.

Synergistic strengthening mechanism of copper matrix composite reinforced with nano-Al2O3 particles and micro-SiC whiskers

Abstract Although Cu–Al2O3 composites have good comprehensive performance, higher mechanical properties and arc erosion resistance are still required to meet heavy-duty applications such as electromagnetic railguns. In this work, a novel hybrid SiCw/Cu–Al2O3 composite was successfully prepared by combining powder metallurgy and internal oxidation. The microstructure and mechanical behavior of the SiCw/Cu–Al2O3 composite were studied. The results show that nano-Al2O3 particles and micro-SiCw are introduced into the copper matrix simultaneously. Well-bonded interfaces between copper matrix and Al2O3 particles or SiCw are obtained with improved mechanical and arc erosion resistance of SiCw/Cu–Al2O3 composite. The ultimate tensile strength of the SiCw/Cu–Al2O3 composite is 508.9 MPa, which is 7.9 and 56.1% higher than that of the Cu–Al2O3 composite and SiCw/Cu composite, respectively. The strengthening mechanism calculation shows that Orowan strengthening is the main strengthening mechanism of the SiCw/Cu–Al2O3 composite. Compared with Cu–Al2O3 composite, the hybrid SiCw/Cu–Al2O3 composite has lower arc time and energy and better arc stability.

Structure Optimization of Electromagnetic Railgun Armature Based on Machine Learning

The armature is an important part of the electromagnetic railgun. It may break, wear, and transition during the working process, which increases the difficulty of maintaining the railgun and impairs the service life of the railgun. Therefore, studying the armature structure of the electromagnetic railgun is of great significance to the design of the electromagnetic railgun. This paper selects the five armature structure parameters of armature shoulder thickness, tail length, wing tip thickness, front end thickness, and interference, and focuses on "using armature structure parameters to predict prestress" and "using prestress and other armature to predict the interference of structural parameters". This paper uses the linear regression method in machine learning to construct the model, and use the normal equation method and the regularized normal equation method to optimize the loss function. The results show that the normal equation method is generally effective for the electromagnetic railgun structure optimization problem discussed in this paper.

Design of Simulated Magnetic Gun

STM32F103 single-chip microcomputer is used as the control unit of the simulated electromagnetic squint. The single-chip microcomputer is used to control the function of launching shell and steering gear angle, and the steering gear is used to control the launching angle and direction of the electromagnetic squint. In the design of electromagnetic gun, coaxial coil gun is used as the main part, and two batteries are used as the energy supply device. Then the electromagnetic relay connected with the single-chip microcontroller controls the cycle charging. Firstly, 12V DC power is input into the circuit by the DC stabilized voltage power supply. After the current enters into the circuit, it is divided into two branches. One branch flows through the boosting circuit of electromagnetic relay to charge the thyristor capacitor. With the switch off, the instantaneous discharge of the capacitor generates an inverter magnetic field in the coil, which pushes the metal projectile out at a high speed. What the electromagnetic relay does is to boost the voltage. What the thyristor capacitor needs is high voltage current charging. Another branch supplies 5V DC power to the steering gear through the step-down electromagnetic relay to support the rotation of the steering gear. The system obtains the target position through openmv, and STM32 uses PWM wave to control the rotation angle and direction of the steering gear.

Combined Fuzzy Time Series Prediction Method for Fault Prediction of EML Pulse Capacitors

Metallized film capacitors are an important part of the electromagnetic rail launch system. It is of great significance to predict its failure. In engineering, the failure law of capacitor is obtained by cyclic pulse accelerated life test of capacitor module with a small number of samples, and is used to predict the actual failure of capacitor in electromagnetic launch (EML) system. This method has the following problems: first, there are few samples of capacitor in life test at affordable cost, which cannot include all capacitor characteristics; second, the time interval of actual EML missions and the voltage of the capacitors are both changing and inconsistent with the conditions used in the life test; third, the statistical law is affected by the measurement and other errors. For these reasons, the prediction accuracy of the existing methods is limited. In this article, a new combined time series prediction method is proposed by using the high-order fuzzy time series prediction theory. Based on the capacitor used in the prototype of an electromagnetic railgun, the life test data of 20 pulse capacitors are used as the prior knowledge input, and the prediction model is obtained. Five groups of capacitor life test data simulating real launch conditions are used as test data to verify that the prediction accuracy of the proposed method is better than that of the traditional method, and the prediction accuracy of capacitor capacitance, which made by different processes, is much higher than that of the traditional method.