Measurement and Formulation of Velocity, Attitude, and Trajectory of Moving Object Using Magnet–Coil Method for High-Speed Penetration Experiment

Abstract

Objects penetrating sand produce various phenomena; however, most phenomena are still unknown. It is necessary to observe the behavior of objects penetrating to sand elucidate these gaps in knowledge. Therefore, the study of projectile impacts requires accurate determination of projectile path and velocity. In order to clarify the location of a projectile after penetrating into opaque material (e.g., sand), the previously developed magnet–coil method using electromagnetic induction was applied. The method provides multipoint measurements of the location of a moving magnet in opaque material. Previous experiments confirmed that it has sufficient measurement accuracy in the case of straight penetration. However, our previous experiments demonstrated that the penetrating projectile meandered. Therefore, in this study, we conducted free-fall experiments in consideration of eccentricity, inclination, and oblique passage of a falling object and evaluated the output signal of the coil. As a result, theoretical equations were formulated for the output voltage induced by the attitude and trajectory of the magnet.