Search

The analysis of the reluctance coil launcher (RCL) basically relies on the finite element method (FEM), but the method is time-consuming and does not meet the real-time requirements for control, which seriously hampers the expansion of engineering application areas. To address this problem, this study proposes a numerical calculation method dedicated to RCL based on the mathematical equations of electromagnetic coupling, in which the magnetic saturation problem is corrected by the inductance lookup table method, and the inductance in the coupling circuit is updated in real time according to the instantaneous current and the instantaneous position of the projectile. The accuracy of the calculation method is verified and the reasons for the errors are analyzed by establishing finite element simulation model, MATLAB/Simulink model and experimental platform for a single-stage and a three-stage RCL and comparing the obtained data. When the discharge voltage of the capacitor is 300 V, the accuracy of the projectile muzzle velocity in the single-stage and three-stage is 98.42% and 98.20% respectively, which indicates that the calculation method is correct under specific conditions. The time consumed by the method is only about 1/1000 of that of FEM, which even includes the compilation time of the software MATLAB/Simulink, illustrating the advantages of the algorithm and its application prospects.

Reluctance coil launchers usually use a pulse current formed by capacitive discharge to excite the excitation coil when launching. The pulse current peaks are high, and the projectile usually undergoes deep magnetic saturation, resulting in low launching efficiency. To address this problem, this article proposes using distributed feeder circuit to drive reluctance coil launchers, replacing the traditional single set of large-capacity capacitor discharge scheme with multiple small-capacity capacitors discharged in a time-sequential manner, so as to reduce the peak current and suppress magnetic saturation problems. The study includes two main aspects, one is to study the effect of the driving method on the launch performance and analyze the reasons; the other is to propose the calculation of the time-varying data in the launch process by the time-segmented calculation method. The efficiency of the model described in the paper is only 1.301% when using a single high-capacity capacitor for launching, while the launching efficiency is increased to 3.535% when driven by the distributed feeder circuit, indicating that the method can effectively improve the launching performance.

In this study, a method is proposed to obtain the initial voltage of the capacitor and the initial relative position of the projectile of a reluctance coil gun using a genetic algorithm to make the projectile launch at a specified muzzle velocity with high efficiency. Firstly, the equivalent inductance change during the launching process is used as a link for multi-physics field analysis, and a set of electromagnetic dynamics equations is derived to correct the effect of magnetic saturation on the inductance according to the current value in the coil. Further the set of equations is constructed as a Simulink discretized numerical computational program and called by a genetic algorithm written in MATLAB to approximate the optimal solution by generation-by-generation optimization. When the specified projectile muzzle velocity is set to 10 m/s, the initial voltage of the capacitor calculated using the genetic algorithm is 156 V, and the initial position of the projectile is −14.3 mm. We input the parameters into the finite element analysis model and the launch experiment platform, and the obtained projectile muzzle velocity is 9.67 m/s and 9.8 m/s respectively, and the efficiency is close to the optimal value, also the comparison of voltage and current waveforms show that the method proposed in this study is effective.

Abstract The aim of this study is to determine the electromagnetic field spatial distribution and longitudinal end effect characteristics of short primary linear induction motor (SPLIM) in the field of electromagnetic launch. First, in accordance to the electromagnetic model assumption of SPLIM and one‐dimensional electromagnetic field theory, the analytical expression of the whole‐region magnetic flux density of air‐gap is derived using electromagnetic field boundary conditions in line with the actual physical meaning. Second, the finite element method used in comparing the analytical calculation values of key physical quantities, such as air‐gap flux density and secondary eddy current in a multidimensional manner under various static and dynamic working conditions and verifying the correctness of the analytical calculation of the electromagnetic field. On this basis, the air‐gap flux density of SPLIM is decomposed according to the different generation mechanisms, and the spatial distribution of each part of the flux density is studied. Spatial Fourier analysis of flux density is conducted, the end effect coefficient is defined, and the change rule of the end effect coefficient with the design parameters of the motor is studied. Finally, a megawatt‐class high thrust prototype test platform was built, and the measured electromagnetic force was compared with the electromagnetic force calculated by air gap magnetic field and secondary eddy current. The steady‐state error of the two was less than 2%, which verified the accuracy of the analysis and calculation.

In view of the problem that the output thrust of the solenoid actuator is affected by various factors and is difficult to calculate in actual working conditions, this paper proposes a semi-analytical model constructed by magnetic field subdomain method with internal and external boundary conditions in a cylindrical coordinate system for calculation, and the general solution equations of magnetic vector potential for each subdomain are derived and solved by MATLAB. Taking a push–pull electromagnet as an example, the finite element simulation and experimental comparative analysis are carried out. The correctness and applicable conditions of the subdomain method are illustrated by comparing the gradient plot of magnetic vector potential, inductance curve and electromagnetic force. It is shown that the results calculated by the subdomain method are very close to the finite element method when the magnetic saturation problem is neglected. However, when the nonlinearity of core permeability is considered, the magnetic saturation gradually deepens with the increase in current, and the error of the subdomain method calculation results gradually increases. Through simulation and experimental verification at slight magnetic saturation, the output thrust after considering the core gravity, spring force and electromagnetic force, it is shown that this method has the advantage of computational flexibility compared with the finite element method, and it is easier to write special algorithms according to various working conditions to calculate the important parameters in engineering applications.

The structure of the reluctance electromagnetic launcher (REML) is equivalent to an inductor with a movable iron core. The dynamic current in the launching process is easy to be measured by instruments, but the data such as the position, velocity of the projectile and the equivalent inductance are not only difficult to solve by analytical methods, but also difficult to measure by instruments, which seriously hinders the development of the control technology. To solve this problem, referring to the method of introducing the inductance matrix into the motor algorithm model to realize semi‐analytic calculation, a special algorithm model is proposed to calculate the launch process data of REML based on the current data. According to the working characteristics of the reluctance coil transmitter, it is pointed out that its inductance matrix should be specifically expressed as a three‐dimensional data table rather than a traditional two‐dimensional table. The current can be obtained by closed‐loop calculation according to the proposed algorithm block diagram when the circuit parameters are known, or measured by instruments when the circuit parameters are unknown, and then the launch process data is obtained indirectly through calculation. In this study, an experimental platform was built, and the algorithm model was established using MATLAB/Simulink. The comparison of the dynamic launch process data of the finite element method (FEM) showed that the method was feasible. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]