Projectile vibration analysis of an electromagnetic launcher
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[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] A novel method for the calibration of accelerometers using an electromagnetic launcher (EML) has been investigated by the University of Missouri. The calibration process utilized is common and well proven, but the proposed method for actuation differs in many regards to common methods. Using an EML for actuation provides many advantages over typical actuation methods such as elastics added gravity, pneumatics, or chemical processes. Actuation force can be precisely controlled with an EML by controlling the current pulse using inductance, pulse width modulation, and capacitive crowbarring. In this way, the calibration of an accelerometer is electronically programmable. The method has been shown effective in controlling acceleration using inductance but a more complete understanding of the mechanical characteristics of the EML projectile which the accelerometer is mounted is desired. From experimental results harmonic resonance has been found in the accelerometer output, and the basis of this research is to determine the root cause of such noise. A detailed computer model of the EML projectile has been created, and simulations of EML operation completed to replicate the experimental findings. The simulation was used to vary geometric parameters, material properties, and to investigate the distribution of driving force on the projectile to eliminate resonant vibrations during firing. Significant evidence has been found to support mechanical vibrations within the projectile as the primary cause of accelerometer resonance found experimentally.
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