The structure and trigger control strategy have become the most important factors that restrict the performance of the multistage synchronous induction coilgun (MSSICG). However, it is still a difficult task to design MSSICG under overload constraint due to coupling between the multiple parameters. In this paper, the maximization of the emission efficiency and acceleration stationarity is treated as a multiobjective optimization problem. By analyzing the relationship between the number of turns and the other structural parameters of the launch, the multiobjective optimization model of MSSICG is established by the current filament method which was verified by the experimental data and finite-element method. And then the second generation nondominated sorting genetic algorithm (NSGA-II) and multiobjective particle swarm optimization (MOPSO) were employed to optimize the model in order to maximize the energy transfer efficiency while achieving the smooth acceleration of the armature. With the formulated optimization model, a five-stage synchronous induction coilgun is optimized as a special case. A decision-making procedure based on the fuzzy membership function is used for obtaining best compromise solution from the set of Pareto-solutions obtained through NSGA-II and MOPSO. In addition, the optimization performance of the proposed multiobjective optimization model and the single-objective optimization model of the MSSICG was compared. The result of optimization shows that the proposed multiobjective optimization model of MSSICG can effectively improve the performance of the coilgun compared with the single-objective optimization model which takes of the launch velocity and overload acceleration as the combination objective function or only the launch velocity.

Armature is very important for a synchronous induction coil launcher which can transform the electric energy to kinetic energy and push the load forward. The structure of the armature will influence the kinetic energy conversion efficiency directly. This paper analyzes the armature structure of a capacitor-driven synchronous induction coil launcher. Length and thickness of the armature are analyzed that how these parameters influence the maximum velocity and system efficiency of the launcher. Current filaments model is used to calculate the motion characteristics of a tubular linear induction motors, which is verified by an experiment and finite-element code. Genetic algorithm optimizer is used to calculate the best trigger times of the coils and the maximum velocity under the conditions of different length and thickness of the armature. It is shown that when the armature mass is fixed, length and thickness of the armature will greatly increase the velocity of the armature. The best length of the armature should be almost 2-2.5 times the length of the coil. The best thickness of the armature could be estimated by skin depth.

Theoretically, the energy conversion efficiency of the synchronous induction coil launcher (SICL) can reach 100%, but at present, the test data show that the highest current is only a little higher than 20%, which shows that the efficiency of the coil launcher has a lot of room for improvement. In this paper, three improved schemes are proposed for the topology of the traditional crowbar circuit based on the pulse capacitor to improve the electromechanical energy conversion efficiency of the electromagnetic coil launcher. They are main circuit breaking, crowbar break-off circuit, and crowbar circuit with inductor, respectively. In order to verify the feasibility of the above three methods, a five-stage coil launcher was simulated and analyzed. Then, based on the model, three improved circuits were calculated and analyzed by the finite-element simulation software. The results show that all of the three methods can improve the efficiency of energy conversion to a certain extent. Both the first and second methods have limited effect on increasing efficiency. In addition, they need to add some expensive equipment such as circuit breaker. So, they are not recommended. The third way of increasing an inductor in the crowbar circuit could increase the muzzle velocity and efficiency obviously. The muzzle velocity increased from 30.6 to 35 m/s. The effect of armature capture is reduced which is worthy of recommendation.

Inductive energy storage for pulsed power supplies is considered to have great potential because its energy density is 1 order of magnitude higher than that of capacitive one. Associating with the superconducting technology and the STRETCH meat grinder circuit, which proposed by the Institute of Advanced Technology, a superconducting inductive pulsed power supply (SPPS) circuit has been proposed by using an air-core high-temperature superconducting pulsed power transformer (HTSPPT) in our previous study. It can not only recapture the energy in the leakage flux and slow down the current change in inductors by using a capacitor, but also reduce the coil loss and the power requirement of the primary source by using superconducting inductors. However, it can be found that the SPPS may generate a large residual current during the discharging phase, which results in an adverse influence on the working frequency and the energy transfer efficiency of the whole system. This paper proposes a modified circuit based on the bridge current switching circuit and HTSPPT. The main principle of the circuit is that the recaptured energy in the capacitor and the residual energy in the secondary are used to precharge the primary inductor for the next cycle, which shortens the charging time, generates continuous current pulses, and improves the energy transfer efficiency. The procedure of the repetitive SPPS is analyzed in detail, and simulations are carried out to explain how the circuit works clearly.

At present, the boost payload of electromagnetic coil launcher mainly adopts integrated launching mode; that is, the armature and payload are integrated into a projectile to shoot out of the bore together. There are some problems with this kind of launching form, such as high parasitic mass and low efficiency of payload launching. In this article, a payload projection scheme of armature-load separation launching is proposed. When the armature and payload reach the peak velocity, the armature is separated from the payload by electromagnetic capture force, and the armature can be recovered and reused under certain conditions. A model of five-stage coil launcher is established and the interior trajectory characteristics of armature under the integrated launching and separation launching modes are compared by simulation. It is shown that the mass of armature will exaggerate the launching performance. The armature-load separated launching mode can effectively improve the launching efficiency. Then the armature recovery method is further proposed. The armature velocity is related to many factors such as mass ratio of armature and payload, driving voltage, and turns of the last coil stage. The study proves that under certain conditions, the armature can be recovered, which could improve the safety of launch.

With the development of semiconductor switches in recent years, inductive energy storage has shown a good application potential in pulsed-power supplies. In our previous studies, a repetitive inductive pulsed-power supply (IPPS) circuit topology was proposed to generate continuous current pulses. An insulated-gate bipolar transistor (IGBT) is used as the main switch to cut off the charging current in this topology. Limited by the current turning off ability of the main switch, it may encounter difficulties in expanding to higher charging currents. In this article, with the concept of inverse current commutation with semiconductor devices (ICCOS) switch, which is proposed by the German-French Institute of Saint Louis (ISL), an improved repetitive IPPS circuit topology is proposed by using a bridge current commutation unit as ICCOS. The thyristor acts as the main switch in the improved circuit and the charging current is turned off by a precharged capacitor. To turn off the charging current for the next cycle, the capacitor can be self-charged by the leakage flux of the pulse transformer and the back electromotive force from the load. Other than that, when the load current pulse reaches the required width, the residual energy of the system can be recovered by switching the inductor to the charging state. Simulation and comparative study show that the improved circuit is suitable for the generation of repetitive current pulses in high-energy systems.