In order to evaluate the electromagnetic launch effectiveness and understand the corrosion damage of the electromagnetic launcher, it is necessary to master the magnetic field data in the bore. At present, there is no related research on the measurement of the bore magnetic field of the electromagnetic launcher. Therefore, a small-scale projectile-borne measuring apparatus based on B-dot probe is developed in this paper. This apparatus uses FPGA as the core. Through the static magnetic field measurement experiment, the data of the induced voltage and the induced magnetic field can be obtained. The projectile-borne magnetic field measuring apparatus designed in this paper can accurately measure the bore magnetic field of the electromagnetic launcher, which lays the foundation for further analysis of the influence of the electromagnetic field in the bore on the launch effect and investigation of the corrosion damage of the electromagnetic 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.
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