Simulation of an electromagnetic in-bore projectile velocity sensor for a high-speed ballistic cannon

The design is described, and a mathematical model is developed for the operation of the measuring frames of a speed sensor for a projectile when it moves within a bore or behind its muzzle. In measuring sections, the frames generate magnetic fields that act as magnetic barriers for the projectiles. The operating principle is based on the effect of deformation of the magnetic field of the barriers due to the electrically conductive projectile. The magnetic circuit of the frame includes an open magnetic core with measuring coils, a coil generating a constant magnetic field (or a permanent superimposed magnet), and a protective cap made of durable nonmagnetic metal with high resistivity. The mathematical model takes into account the 3D interaction of the projectile with the magnetic field of the barrier and the effect of induction currents in the protective cap on the magnitude and shape of the signals. The results of parametric studies on the effect of the speed, shape, and size of the projectile bodies, as well as the main parameters of the measuring frames, on the magnitude and shape of the signals generated by the projectile are presented.