Coilgun Design Research Articles

Coilgun design and evaluation without capacitor

Capacitors with high voltage and capacity values are used in most induction coilguns that are designed and constructed. The fact that capacitors are quite bulky and slow in energy transfer and how a coilgun can be made without using capacitors is the study subject of this article. Two and four coil gun samples were made to find the essential components of an electric gun, and the results are reported in this article. The accuracy of the results is also confirmed by FEMM analysis for these models. The harmony of experimental and theoretical results shows that smaller and low cost portable electrical weapons can be a powerful alternative to firearms in the future.

Linear electromagnetic accelerator

Over time, the weapons have been based on mechanical energy (bows, catapults) and chemical energy (guns, missiles), however, at the moment, more and more weapons are designed using electromagnetic energy (railgun, coilgun). The focus of this paper is to obtain the desired muzzle velocities of a projectile according to the existent current. In the first part of the paper, the railgun and coilgun design are presented along with their most important advantages. Based on these observations, a new design of an electromagnetic launch system is presented. Next, Maxwell interactive software package was used that applies the finite element method (FEM) to analyze and solve 3D electromagnetic field problems in order to analyze the variation of acceleration force, speed in time. All simulation data shows that this design has a great potential, because of the adaptability to different applications.

Physical analysis and optimization of electromagnetic coilgun launch systems

Coilguns are one of the most widely used projectile launch systems using electromagnetic force. The ideal coilgun would propel a projectile with maximum velocity while also having a high power efficiency. The physics of coilguns is well understood; however, optimizing the coilgun design is much more difficult, as it requires the consideration of the parameters of every component of the system, such as the coil, projectile, and power supply. In this paper, electromagnetism, kinematics, and electrical circuit theory are employed to analytically describe the operations of a coilgun with permanent magnetic projectiles. These analytical equations are then implemented using mathematical programs. Coilguns with distinct design parameters and current profiles can be tested numerically to quickly find the optimal combinations to achieve the maximum velocity or power efficiency. The results are presented and measurements are utilized to verify the predictions.

Acceleration Mechanism and Experimental Research of Multi-Stage Synchronous Induction Coilgun Based on Magnetic Field Arrangement

Multi-stage synchronous induction coilgun is one of the important research aspects of the electromagnetic launch. Researchers mainly focus on the optimization of the geometrical dimension and parameters for the multi-stage launcher, pulsed power supply, armature, and so on, in order to achieve the best matching between parameters. Based on the basic principle of multi-stage induction coilgun, the acceleration mechanism is investigated in terms of the magnetic field arrangement. First, a field-circuit coupled model for a 15-stage coilgun is built. Through analyzing the velocity profile and the distribution of current density vector on the armature, it is considered that the armature is affected by the magnetic field generated by frontal stages and current stage during the launching process, so the braking force and pushing force both act on the armature. Therefore, the system conversion efficiency is affected. In order to reduce the braking force and increase the variation of the magnetic field, the direction of the magnetic field is changed. The distribution of the current density vector on the armature and transition process for the variation of the magnetic field is analyzed. The simulation results show that the muzzle velocity can be increased significantly by changing the direction of the magnetic field. The acceleration mechanism of the inconsistent direction of the magnetic field is different from that of a consistent direction. The current density on the armature is increased dramatically in the transition area, which is beneficial to increase the magnetic pushing force. A previously built 15-stage coilgun was used to validate the method. The launching experiments are carried out under the condition of the consistent direction and inconsistent direction of the magnetic field. The experiment results show that the system conversion efficiency is improved significantly for the inconsistent direction of the magnetic field. It provides a valuable reference for multi-stage induction coilgun design.

Two fluxes multistage induction coilgun

This paper presents a brand new induction electromagnetic launcher, which uses two magnetic fluxes in order to accelerate a projectile. One magnetic flux induce a current in the armature and the second magnetic flux is creating a radial magnetic field. This aproach offer multiple advantages over single flux designs. First we are able to control the induced current in armature because we use the coil just to induce current inside the ring with a great efficiency. Second advantage is the angle of 900 between magnetic field density B and the ring. We used the induction to avoid contact between armature and accelerator. In order to create the magnetic field radial we used four coils perpendicular on armature. This approach alove us to control the phase difference between induced current in armature and current in magnetic field coils for a maximum force. The phase difference is obtained by changing the frequency of magnetic field coils power source. We used simulation software to analyze, and simulate a multistage induction coilgun design with two fluxes. The simulation results demonstrated the theoretical results.

Optimization analysis study of a multi-stage SICG based on OED

This paper analyzes the influences of the factors in a capacitor-driven multi-stage synchronous induction coilgun (SICG) and optimal combination of the design parameters based on orthogonal experiment design (OED). Finite element transient solver is used to calculate the motion characteristics of a multi-stage SICG. The muzzle speed is set to be the target of the optimization. System parameters (factors), levels and orthogonal array (OA) are determined by the order. Three optimization schemes are compared, including stage-by-stage optimization, section optimization and full optimization. Optimal combination of the three-stage SICG is obtained, as well as important order of factors. It shows that a set of comparatively better parameters and relatively higher efficiency could be achieved through orthogonal optimum. Wire diameter and coil diameter are the most important factors that influence the system efficiency of the launcher. Besides them, length of coil, trigger position and number of turns have less influence for the system in the important order. Section optimization could reduce the amount of computations compared to full optimization and a set of comparatively better parameters and relatively higher efficiency could be achieved. It is suggested to optimize a multi-stage SICG. How to choose the factors from lots of parameters is according to the engineering practice. Improper choices of the value in levels may cause unable to reach an optimum. The conclusion will be useful for coilgun design.

Coilgun 성능향상을 위한 솔레노이드 코일 설계

This paper reports the design of solenoid in a coilgun for high velocity of projectile in a coilgun system, according to diameter of coil. Coilgun using a magnetic force means a mechanism that can control the magnetic material. When momentarily supply a large current to the solenoid instantaneous magnetic field is created around the coil, the projectile is fired by receiving a magnetic force towards the center of the coil, based on the right-hand rule of Fleming. The velocity of projectile is proportional to the magnetic force generated by the electromagnetic coil. The current affects the life of the coil and the current limit exists. Therefore, the coilgun design, which does not exceed the current limit and the magnetic forces are at the maximum, is required. In this paper, whether it is possible fire looking for the optimal number of turns according to the diameter of the coil from AWG #6 to AWG #18 for the design of the solenoid coil, and comparative analysis firing rate associated with it.

Investigation of Armature Capture Effect on Synchronous Induction Coilgun

To obtain high velocity and high energy conversion efficiency on a synchronous induction coilgun, the armature capture effect which is the inherent characteristic for the synchronous induction coilgun needs to be analyzed. The reason for the armature capture effect is first deduced and analyzed using the lumped element circuit model and then quantificational result is obtained based on the field-circuit coupled model. According to the analytical result, the method to minimize the armature capture effect is proposed from the viewpoint of the magnetic coupling between the driving coil and the armature. Several ways are analyzed through the finite-element simulation. The simulation results show that adjusting the power parameters, such as increasing the capacitance or initial voltage, and decreasing the crowbar resistance, and adjusting the armature parameters, such as decreasing the mass or adopting the solenoid armature, can minimize the armature capture effect and increase the conversion efficiency. These methods are validated through a four-stage induction coilgun. We compare the simulation results with the experimental results and show that by adjusting the armature parameters, we can minimize the armature capture effect. It provides valuable reference for synchronous induction coilgun design.

Design and Evaluation of the Driving Coil on Induction Coilgun

Driving coils in a multistage induction coilgun are stacked end to end forming a barrel. During launching, the pulsed current flows through the driving coil, and the electromagnetic force propels the projectile ahead. The driving coil endures not only the radial expansionary force because of the magnetic flux compression, but also the axial force due to the compressive force and counterforce of the projectile. In the process of coil design, both the mechanical strength and the electrical insulation must be considered. Due to the nonlinearity of insulation materials, the theoretical calculation cannot reflect the true state for the driving coil. The conventional static-state test method is analyzed and verified through experiments. The experimental results show that this method is ineffective for the multistage launching, because it neglects the axial counterforce and does not reflect the true state of launching. An improved method for evaluating the coil strength is proposed based on the analysis of the basic principle. The projectile is accelerated by the former stages, and the testing coil accelerates the projectile with an initial speed. Equipment for testing single coil is designed and installed in the muzzle of the existing multistage coilgun. The experimental results show that this method can test the coil's mechanical strength and electrical insulation more effectively than the conventional method. The dynamic-state method can be used to approximately evaluate the performance of different types of the coil. The structure of the driving coil can be improved through testing and evaluating, which provides experimental reference for the multistage induction coilgun design.

전자기 발사장치에 적용 가능한 코일건 설계 및 실험

본 논문은 전자기 발사체에서 피투사체의 높은 발사력을 위한 코일건 설계 및 실험을 다루고 있다. 현재 코일건은 전자기 발사체에 적용하기 위해 많은 연구가 진행되고 있다. 코일건은 솔레노이드 형태의 코일에 전류 인가 시, 플레밍의 오른손 법칙에 의하여 발생하는 전자기력에 의해 피투사체를 추진시키는 원리이다. 피투사체의 발사력은 코일에 흐르는 전류가 생성하는 자기력과 비례한다. 전류는 코일의 수명에 영향을 미치므로 전류의 한계점이 존재한다. 따라서, 전류의 한계점을 초과하지 않고 피투사체가 받는 자기력이 최대가 되는 코일건의 설계가 요구된다. 이를 위해 먼저 코일건의 자속밀도, 자기력을 계산하고, Onderdonk's 식을 이용하여 코일의 전류 한계점을 찾는다. 솔레노이드를 설계하기 위해서 전류 한계점을 초과하지 않는 조건을 만족하며 코일건의 자기력을 최대로 가지는 권수를 알아낸다. 설계 결과에 따라 시제품을 제작하여 피투사체의 속도를 측정하기 위한 실험을 하였다. 발사된 피투사체는 CCD 카메라를 이용하여 촬영 및 분석하였으며, 평균속도 21m/s임을 알 수 있었다. 또한, 상용 전자기 해석 소프트웨어 MAXWELL을 이용한 자속 밀도 해석값와 실험값을 비교한 결과, 오차는 약 9.5%이었다. 【This paper reports the design and experiments for a high drive force of projectile in a coil gun system. Currently, the coil gun has been studied to apply an electromagnetic launcher. A coil gun launches a projectile by the attractive magnetic force of the electromagnetic coil. The drive force of projectile is proportional to the magnetic force generated by the electromagnetic coil. The current affects the life of the coil and the current limit exists. Therefore, the coil gun design, which does not exceed the current limit and the magnetic forces are at the maximum, is required. For this purpose, this study calculated the magnetic flux density and forces of the coil gun system and determined the current limit of the coil using the Onderdonk's equation. Based on the design result, a prototype was manufactured and an experiment was conducted to measure the muzzle velocity of the projectile. The fired projectile was analyzed using a CCD camera, and the muzzle velocity was 21m/s. In addition, a comparison of the experimental value and analysis value using commercial electromagnetic analysis software MAXWELL revealed an error of approximately 9.5%.】

电磁线圈炮计算程序的收敛性与实验验证

电磁线圈炮计算程序的收敛性与实验验证

On the Design of Coilguns for Super-Velocity Launchers

This paper deals with the design of a super-velocity launcher with muzzle velocity up to 8 km/s. It addresses the design specifications of the linear induction section of the launcher having a 4-km/s breech velocity, and utilizing a projectile weighing 1 kg. The overall launcher is a hybrid design, using a gas gun to obtain the initial 4-km/s speed at the input to the coil launcher. The design sequence starts with the maximum temperature allowed by the sleeve material; continues by selecting the required number of sections in the barrel; the dimensions of the drive coils are determined; and our existing computer code is used to optimize the transition between the gas gun and the first section of the coil gun, and between successive sections of the barrel. The code utilizes our latest design scheme; that is, the drive coils are connected in parallel; one flywheel generator per pole is used; and all of the generators in a given section are shaft-coupled, so that they all rotate at the same speed. The design specifications are presented in this paper together with simulation results for the phase voltages, the currents, and the acceleration forces

Operational requirements and issues for coilgun electromagnetic launchers

Coilgun electromagnetic launchers have capability for low- and high-speed applications. Through the development of four guns having projectiles ranging from 10 g to 5 kg and speeds up to 1 km/s, Sandia National Laboratories has succeeded in coilgun design and operations, validating the computational codes and basis for gun system control. Coilguns developed at Sandia consist of many coils stacked end-to-end forming a barrel, with each coil energized in sequence to create a traveling magnetic wave that accelerates a projectile. Active tracking of the projectile location during launch provides precise feedback to control when the coils are triggered to create this wave. However, optimum performance depends also on selection of coil parameters. This paper discusses issues related to coilgun design and control such as tradeoffs in geometry and circuit parameters to achieve the necessary current risetime to establish the energy in the coils. The impact of switch jitter on gun performance is also assessed for high-speed applications.

On the design of a coilgun as a rapid-fire grenade launcher

Two electromagnetic grenade launcher designs for armored vehicles are described. Both are based on the specifications for a conventional launcher, the Mark 19, which uses an M430 projectile. The first launcher has a muzzle velocity of 241 m/sec, as does the conventional one. For the second, the muzzle velocity was increased to 700 m/sec. Because of the large difference between the two velocities, the two designs had to be based on different energy considerations. The effects of variations of barrel parameters such as the pole pitch, the number of sections, and the thickness of the coils, are examined. For the projectile, the sleeve length parameter is varied. General guidelines are presented for the design of grenade coilguns.

Thermal and mechanical stress in induction coilguns

The aim of this paper is to define a procedure for the design of induction coilguns in order to obtain thermal and mechanical stress that do not exceed the allowed values in the sleeve. The magnetic vector potential is determined considering a cylindrical sheet current model both for the barrel and the sleeve and solving the related modified Bessel equation. Then the flux, the current density and the propulsive force for each section are determined. By considering the constraints due to mechanical and thermal stress, the maximum muzzle velocity for a one-section launcher is determined. Supposing that the muzzle velocities in the first and in the last section are established, and assuming that all sections, from the second to the last, work with the same mean slip and the same relative velocity, the number of sections and their length are determined. Moreover the surface current density in the barrel is calculated. The design criterion is compared with other criteria, and then used to design an 8 km/s muzzle velocity launcher.

Pulsed coilgun limits

The design of coilguns is commonly based on a 'try and see' basis using an analytical model to ascertain its performance. This paper examines the use of formal optimisation techniques to explore the performance limitations of pulsed coilgun technology. The optimisation procedure is constrained by the material, mechanical and thermal properties and seeks to determine the coil geometry that achieves the maximum velocity for a given payload. The paper illustrates the maximum velocity achievable for several different payloads as a function of the coilgun length and bore diameter.

Design of pulsed coil-guns

The paper describes a two-step procedure for designing pulsed coil guns to suit a given power supply. The stator is designed coil-by-coil using an overlapped optimisation procedure that takes account of inter-coil coupling. The armature is designed by notionally removing material from an oversize blank on the basis of a utility factor calculated from the local force distribution.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Coilgun technology at the Center for Electromechanics, the University of Texas at Austin

The engineering trade-offs performed on a coilgun design are described. The concept used was that of a collapsing field accelerator. This concept was chosen because of its passive operation, and because it lent itself to existing power supplies. The trade-offs described concern stress, maximum temperature rise in conductors, efficiency, time constants of the energy storage element, and weight. An example of such a trade-off concerns the mass of coilgun armatures. The more massive an armature, the greater its ability to absorb resistive losses and the higher its time constant. However, larger armature lower payload efficiency. Another trade-off concerns the fraction of armature weight that is devoted to structure. More highly stressed armatures have more attractive electrical performance at the expense of parasitic weight.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Analysis of induction-type coilgun performance based on cylindrical current sheet model

A method which is based on a cylindrical current sheet model for the analysis and design of induction-type coilguns is presented. The work starts with a derivation of closed-form formulae which relate the dimensions of the gun to the performance expressed in terms of propulsive and local maximum forces on the projectile, power factor and efficiency of the system, thermal stress of the projectile armature, distributions of the flux density around the launcher, and the system parameters in a multisection coilgun. A numerical example is given. >

Guidelines for the design of synchronous-type coilguns

Smooth acceleration and evenly distributed mechanical and thermal stresses can be achieved in a coilgun-type electromagnetic launcher by the interaction between an electromagnetic wave-packet traveling along the barrel and a moving cylindrical conductor (sleeve) carrying a system of currents. The barrel consists of an array of cylindrical coils energized by polyphase currents; a sinusoidal distribution of azimuthal currents is impressed on the sleeve. Design guides and scaling laws are developed for such a launcher. It is shown that muzzle velocities up to 10 km/s might be attainable with a barrel length of less than 15 m with high efficiencies. However, for velocities far in excess of that range, the need to maintain the physical integrity of solid armatures leads to barrel lengths which may be impractical for most applications. >