Semi Active Control of sinusoidal shock waveform on drop test machine (DTM) using non-linear dynamic model of hybrid wave generator (HWG) consisting of rubber and electroMagnet.

This article focuses on the development and experimental validation of a novel Hybrid Wave Generator (HWG) designed to produce variable shock pulses in Drop Test Machines (DTMs) through semi-active control of stiffness. The HWG combines the fixed stiffness of a Rubber Wave Generator (RWG) with the variable stiffness generated by the interaction of a permanent neodymium magnet and an electromagnet powered by capacitor discharge, enabling control over shock pulse height and duration by adjusting voltage. Mathematical nonlinear modeling and experimental tests demonstrate that the HWG can vary average stiffness from 32 to 74 kN/m, resulting in shock pulse height changes from 18 to 56 g and pulse width variations exceeding 5 ms, with good agreement between predicted and measured results. The study highlights the nonlinear hardening and softening effects on pulse shape due to rubber and magnetic forces and discusses practical considerations such as electromagnetic shielding and limitations related to specimen magnetism and mass. This work provides a semi-active, energy-efficient approach to generating customizable shock waveforms without the need for physically replacing RWGs in DTMs.