Electromagnetic Railgun System Research Articles

A Fuzzy Controller for PFN Trigger Time Sequence in Electromagnetic Railgun System

For the electromagnetic launch system, how to realize the wide pulse, fast rise, and small fluctuation of pulse forming network output current is a core problem. A trigger time sequence control method based on fuzzy theory for the pulse forming network is proposed in this paper. First, circuit models of pulse forming unit, pulse forming network, and electromagnetic rail launcher is established. Second, a fuzzy trigger time sequence controller model for pulse forming network is designed by using Simulink. Third, fixed time sequence discharge tests consisting of 20 pulsed forming units on the linear simulation load are carried out to verify the accuracy of the simulation model. Finally, discharge tests on the linear simulation load and launch tests on the electromagnetic railgun are carried out to verify the precision of the fuzzy controller output respectively. The results show that the designed fuzzy trigger time sequence controller can obtain the ideal trigger time sequence, which demonstrates the pragmatic and reliability of fuzzy control algorithm.

Optimization of the Current Control for the Pulsed Power Cables of the Electromagnetic Railgun

The current control of the breech pulsed power cables and the stability of the total current are important factors which have an influence on the performance of the electromagnetic railgun system. In order to achieve these two targets, a two-objective optimization model through the genetic algorithms and weighted combination method is established. An optimization example of 20-mm railgun with 1-MJ fixed energy storage is given. The results show that the methods can be satisfied to the optimization design under the following premises. The reference value for the mean square error of the pulsed power cable peak current which represents the degree of the current control is selected between 1.5 and 4 kA, and the reference value of the compression ratio which represents the stability of the total current depends on the average compression ratio of the initial population. The mean square deviation of the best individual can be reduced to 600–750 A, and the compression ratio can be increased to 0.64–0.68 when the peak value of the total current is limited between 500 and 560 kA.

Research on armature vibration characteristics of electromagnetic gun’s extreme sliding electrical conta

The electromagnetic railgun is a new launch method that uses electromagnetic force to drive payloads and accelerate objects to super high speeds. In the electromagnetic railgun system, the armature is a key component that converts electrical energy into kinetic energy of projectile. It will vibrate when it moves between rails, and the vibration characteristic is the behavior when the armature slides along the rail. Armature vibration will affect firing accuracy, damage integrity of rail, and affect life of rail. Armature vibration may also cause arc discharge, which will damage the armature, consume energy, and reduce the launching efficiency of the electromagnetic railgun. In order to provide a more reasonable design for the armature, based on the finite element simulation software ANSYS, a modal analysis was performed on the armature during the launch process, and the possible modes of its free vibration were simulated. The analysis found that the vibration modes are mainly divided into translational movements along the X, Y, and Z directions and torsional movements along the X, Y, and Z axes. Whether or not the prestress is loaded on the armature and the magnitude of the prestress does not significantly affect its vibration mode. Changing the armature structure and materials will affect the vibration mode of the armature accordingly.

Real-Time System-on-Chip Emulation of Electrothermal Models for Power Electronic Devices via Hammerstein Configuration

Real-time emulation of device-level power electronics plays an essential role in many industrial applications for design and hardware-in-the-loop testing of system components and controllers. Due to the complexity and heavy computational burden of the real-time hardware implementation of the analytical and the numerical models, this paper proposes dynamic electrothermal behavioral models for diode, thyristor, and insulated-gate bipolar transistor based on the Hammerstein configuration. The power electronic device model parameters are extracted from the known device datasheets and implemented in Zynq System-on-Chip platform with accelerated processing for real-time application. An electromagnetic rail gun system has been employed as the study case to compare the performance of the proposed electrothermal behavioral models with that of off-line simulation models on SaberRD software.

Thermal Analysis on Electromagnetic Launcher Under Transient Conditions

Since a tactical electromagnetic railgun system is required to fire several times a minute, the thermal load on the rails leads to a higher temperature, which will even result in launch failures and reduce the life span of the launcher. In this paper, the rail temperature was measured during the launch experiment. Furthermore, based on a 3-D transient model with moving armature, mechanically, thermally coupled electromagnetic field analysis using finite-element method is presented. The Joule heating is one of the main heat sources in the rails. Contact resistance and friction force that cause heat between the armature and the rail are also included in the model. The simulation results show that the peak temperature in the rail occurs at the inner surface. Overall, along the direction of armature motion, the temperature of the rail near the breech end is higher than at the muzzle end, and the maximum temperature on the rail appears near the initial position of the armature. The contact resistance contributes much more than friction to the temperature rise in rails.

Performance Evaluation of Electromagnetic Railgun Exterior Ballistics Based on Cloud Model

Exterior ballistics performance evaluation plays a critical role in the design and development of the electromagnetic railgun system. The ballistics performance evaluation can be regarded as a multicriteria decision-making problem, for the reason that various characteristics, also termed criteria, have effects on the overall performance. A sophisticated simulation model, including six-DOF mechanics, railgun configuration, environment, and aerodynamics models are established to compute the exterior ballistics profile. Then a comprehensive framework based on cloud model and analytic hierarchy process method are proposed to evaluate ballistics performance. Eight criteria including ballistics velocity, energy efficiency, flight time, flight range, overload, attack angle, and sideslip angle stability are selected to determine exterior ballistics performance. The proposed approach yields the certainty degree of each criterion and integrates multicriteria into the whole performance. Two scenarios including 32-MJ launch energy and 200-km strike range are taken to generate alternatives for assessing ballistics performance, which demonstrate the proposed approach is feasible. Results show that in the same launch energy 32 MJ, the performance levels of 12- and 16-kg projectiles are I (excellent) and III (medium), respectively. Besides, gaining the projectile’s mass can improve performance in the same strike range 200 km.

Performance Analysis and Parameter Optimization of CPPS-Based Electromagnetic Railgun System

A fast solving method for the launching process of the electromagnetic railgun and an automatic assignment method for the trigger strategy of the capacitive pulsed power supply (CPPS) are proposed. The accuracy of the solving method and the feasibility of the assignment method are verified through an illustrative example with a 1.8-MJ initially stored energy. On the basis of these methods, parameter optimization in design phase and performance analysis in operation phase are conducted around the projectile muzzle kinetic energy $E_{k}$ and the system energy transfer efficiency $\eta $ . To be specific, the single-objective optimal solutions of $E_{k}$ and $\eta $ and the biobjective Pareto front of $E_{k}$ – $\eta $ are acquired by evolutionary computation. And the influence relations of certain system parameters on $E_{k}$ and $\eta $ are acquired by parameter sweep. The research methods and results in this paper have both theoretical and pragmatic values in improving the performance of the CPPS-based electromagnetic railgun system.

Design Considerations of an Air-Core Pulsed Alternator in an Electromagnetic Railgun System

An air-core pulsed alternator is extremely attractive for driving the electromagnetic launchers. The reason is that the machine can offer high voltage and current performance in a single-element energy storage device, a smooth pulse profile, and naturally cycled current zeros, which can allow for extremely low muzzle currents and simplifies switching requirements. But because of the short history of the air-core pulsed alternator in China, the relevant theoretical research is not enough and the experience in fabrication is absent. It is really necessary to summarize a preliminary design method in order to rapidly determine the size and approximately evaluate the electrical performance of the machine. The optimization will be based on this first-stage design scheme. In this paper, based on the requirements of the railgun, some important design considerations of a seven-phase and six-pole air-core pulsed alternator are presented in detail. In addition, it is significant to obtain the analytical formulas for the first-stage design requiring less costs; these formulas intuitively allow us to expedite the design process and optimize the design scheme. Finally, some basic output parameters of the machine are given for the preliminary design; the designed pulsed alternator will generate 1.4 kV and drive a train of 1-MA pulses into a 5-m railgun, accelerating 200-g masses at 2 km/s.

Influences of Electric Parameters of Pulsed Power Supply on Electromagnetic Railgun System

To analyze the electric parameters of a pulsed power supply (PPS) system and their influence on muzzle velocity, a stable and reliable 200-kJ compact PPS system used for electromagnetic railgun system has been developed. The PPS system consists of ten modules, and each module is comprised of a high energy density capacitor (3270 $\mu $ F/3.5 kV), 4-in thyristor, a pulse shaping inductor (1.5 $\mu $ H), and a crowbar diode. At the same time, a railgun circuit model for simulation was established. In this model, velocity skin effect, current skin effect, and friction were taken into consideration. Some electromagnetic launching experiments were carried out to verify the correctness of the railgun circuit model. Influence of different electric parameters of PPS on muzzle velocity was analyzed by the computer aided circuit design program PSPICE based on this model. The parameters include capacitance, equivalent series resistance (ESR) of the capacitor, inductance, and jitter time of the thyristor. The simulation results show that the ESR is the most critical influencing factor (the deviation of velocity is −4.286% when the ESR is 5 m $\Omega $ ). The following is the change of the capacitance (the deviation of velocity is −3.827% when the capacitance decreases to 95%C0). In the meantime, the changes of the resistance of inductor do have an influence on muzzle velocity (the deviation of velocity is −0.908% when the resistance of inductor is 1 m $\Omega $ ). However, the changes of inductance and the jitter time of the thyristor impose no significant effect on muzzle velocity. The conclusions provide reference to the overall optimization of PPS design and quality control of the manufacturing process.

On electric warship power system performance when meeting the energy requirements of electromagnetic railguns

This paper investigates the ability of a gas turbine alternator to provide power to an electromagnetic (EM) railgun in surface combatants whilst simultaneously maintaining acceptable levels of power quality for other consumers. Following the justification of the investigation and a description of the research methods, which includes a proposed EM railgun charging control system, this paper discusses simulated results obtained from a validated power system model for both single shot and salvo operations and identifies factors that limit the rates of fire in each case. The findings from the investigations suggest that a large gas turbine alternator is able to maintain quality of power supply within acceptable limits for the majority of EM railgun operations. However, the transient quality of power supply limits was found to be exceeded for heavy firing rates but would remain within tolerable limits as defined for exceptional loads by North Atlantic Treaty Organization (NATO) standardization agreement (STANAG) 1008 Edition 9. A method to increase the maximum rate of fire whilst maintaining the quality of the power supply within acceptable limits is investigated by increasing the size of the energy storage device and retaining a residual charge. The paper concludes by suggesting that the EM railgun system could be integrated into the ship's electrical system without the need for any additional prime movers to achieve rates of fire commensurate with a surface combatant's requirements.

Study on the System Efficiency of the Capacitive Pulsed-Power Supply

Electromagnetic railgun systems based on capacitive pulsed-power supply (CPPS) have obtained widespread applications because of its obvious advantages over the inductive ones on mature technology, operational reliability, and feasible financial condition. However, the existing CPPS-based electromagnetic railgun system works with low efficiency. In this paper, systematical studies on the CPPS in the synchronously triggered electromagnetic railgun system with constant volume and in the time-delay-triggered electromagnetic railgun system with automatic segmentation are proposed, respectively. In the synchronously triggered electromagnetic railgun system, all pulse-forming units (PFUs) are supposed to be triggered synchronously and the load is simplified as a resistor first. Then, the system performance criteria, i.e., the launch velocity of the armature vend and the system efficiency η, are expressed as the function of four independent system variables: 1) the capacitance of each PFU C; 2) the precharged voltage U <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</sub> of capacitors; 3) the rail length l; and 4) the armature mass m. The relationship between η (or v <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">end</sub> ) and any two independent variables can be found under the environment of MATLAB R2012a by fixing the other two parameters. The results are then verified under the environment of Simplorer 8. These figures can be used to instruct the design of the pulsed-power supply for a designated load or the railgun for a designated source. In the time-delay-triggered electromagnetic railgun system, the principle of automatic segmentation is proposed. According to the segmentation principle, the simulation results under the environment of Simplorer 8 are given for comparison. The paper can provide a theoretical foundation for the future designs to get higher system efficiency.

Efficiency Analysis of an Electromagnetic Railgun With a Full Circuit Model

An electromagnetic railgun (EMG) fed by a capacitor bank was developed to launch hypervelocity projectiles. The efficiency of the EMG will ultimately determine the scale of its use since it determines the size of the power source. In practice, it is difficult to calculate the energy loss in the EMG system in a simple way, because of complicated physical phenomena such as dynamic friction occurring during firing. In this paper, an expression of the friction in the EMG system is conceived and validated by the measured current and in-bore velocity of the armature. With the conceived expression, a full circuit model, including the effects of the friction in the EMG system, is derived and validated. The simulated current and velocity based on the model are in good agreement with the measurements. The efficiency and energy loss in our EMG system are calculated and analyzed with the full circuit model. The primary mechanisms of the energy loss attribute to the impedance of the rail and pulse formation network.

Analysis of Electric Parameters of a PPS System and Their Influence on Muzzle Velocity in Electromagnetic Railguns

A 500 kJ compact pulsed power supply (PPS) system used for electromagnetic railgun (EMG) system has been developed to investigate the influence of electric parameters on muzzle velocity in the paper, from which the stability and reliability of the PPS system can be evaluated. The pulsed power supply system consists of ten modules, and each module is composed of a high energy density capacitor, a triggered vacuum switch, a pulse shaping inductor, a dump resistor and a crowbar. Influence of different parameters on the velocity was analyzed by ATP simulations in this paper. The parameters include capacitance, equivalent series resistance (ESR) of the capacitor, inductance, natural electric parameter and jitter time of the TVS. The ESR and natural electric parameters are critical influencing factors by comparing the simulation and experimental results. In the end, muzzle velocity deduced by the current, which is obtained from a new model of actual circuit, is about twenty percent lower than that in ideal condition. It is pointed out that the velocity error is mostly caused by ESR and natural electric parameter.

Influence of bore and rail geometry on an electromagnetic naval railgun system

A large-scale railgun is being considered by the U.S. Navy as a future long-range (>200 nm) naval weapon system. The notional concept includes a 15 kg projectile with a 2.5 km/s muzzle velocity. The choice of bore and rail geometry for such a weapon can influence key aspects of the total system design. This study explored a range of bore and rail geometries and looked at their effects on key railgun system parameters such as parasitic mass, inductance gradient, linear current density, required pulse forming network (PFN) size, and barrel mass. Preliminary solid modeling and structural analysis of the integrated launch package was performed in order to quantify parasitic mass. Inductance gradient calculations were based on a current density distribution analysis. A PFN/launcher numerical simulation model was then used to determine linear current density and PFN size. Finally, barrel mass was estimated by structural analysis based on calculated rail repulsive forces. Trends and sensitivities of the different parameters to changes in the bore and rail geometries are presented and conclusions are given.

High-speed hydrogen pellet acceleration using an electromagnetic railgun system

Using a low electric energy railgun system, solid hydrogen pellet acceleration tests have been conducted to investigate the application of the electromagnetic railgun system for high-speed pellet injection into fusion plasmas. Pneumatically pre-accelerated hydrogen pellets measuring 3 mm in diameter and 4–9 mm in length were successfully accelerated by a railgun system that uses a laser-induced plasma armature formation. A 2 m long single railgun with ceramic insulators accelerated the hydrogen pellet to 2.6 km s −1 with a supplied energy of 1.7 kJ. The average acceleration rate and the energy conversion coefficient were improved to about 1.6×10 6m s −2 and 0.37%, which is 1.6 times and three times as large as that using a railgun with plastic insulators, respectively. Furthermore, using the 1 m long augment railgun with ceramic insulators, the energy conversion coefficient was improved to about 0.55% while the acceleration rate was increased to 2.4×10 6 m s −2. The highest hydrogen pellet velocity attained was about 2.3 km s −1 for the augment railgun under an energy supply of 1.1 kJ. Based on the findings, it is expected that the acceleration efficiency and the pellet velocity can be further improved by using a longer augment railgun with ceramic insulators and by applying an optimal power supply.

Railgun pellet injection system for fusion experimental devices

A railgun pellet injection system has been developed for fusion experimental devices. Using a low electric energy railgun system, hydrogen pellet acceleration tests have been conducted to investigate the application of the electromagnetic railgun system for high speed pellet injection into fusion plasmas. In the system, the pellet is pre-accelerated before railgun acceleration. A laser beam is used to induce plasma armature. The ignited plasma armature is accelerated by an electromagnetic force that accelerates the pellet. Under the same operational conditions, the energy conversion coefficient for the dummy pellets was around 0.4%, while that for the hydrogen pellets was around 0.12%. The highest hydrogen pellet velocity was 1.4 km s −1 using a 1 m long railgun. Based on the findings, it is estimated that the hydrogen pellet has the potential to be accelerated to 5 km s −1 using a 3 m long railgun.

Development of Railgun Pellet Injector Using a Laser-Induced Plasma Armature

Using the low electric energy railgun system, dummy pellet acceleration tests have been conducted to investigate the application of the electromagnetic railgun system for high-speed pellet injection into fusion plasmas. The primary objective of the development is to improve the pellet acceleration efficiency and durability of the rail materials. In the system, the pellet is pre-accelerated before railgun acceleration. A laser beam is used to induce plasma armature. The ignited plasma armature is accelerated by an electromagnetic force that accelerates the pellet. As low electric energy was used, rail materials were used for multiple operations. Tungsten-alloy rail provided longer durability and slightly higher energy conversion coefficient than copper rail. The energy conversion coefficient was from 0.3 to 0.5% using a plastic insulator. A ceramic insulator improved the energy conversion coefficient by 80%. The highest pellet velocity was 1.7km/s using wooden pellets accelerated by 1m-long railgun. Based ...

Design considerations in a 60 caliber electromagnetic railgun system

A design code has been developed to aid in the development of a compact 60-caliber EM (electromagnetic) launcher system, based on a standard multivariable optimization technique. A lumped circuit model which was verified with a sophisticated performance program serves as the core of the code. The design code provides an optimum set of 13 compulsator rotor design parameters that minimizes the rotor mass subject to eight design constraints for a single railgun discharge. These design parameters are rotor radius, rotor length, armature conductor thickness, banding thickness, number of conductors per pole, launcher length, launcher inductance gradient, projectile velocity, generator voltage, maximum allowable decrease in rotor angular velocity, pulse width, electrical frequency, and firing angle.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>