experimental study on dynamic characteristics of linear parametrically excited system

an electromagnetic device, acting like a spring with alternating stiffness, has been designed to parametrically excite the cantilever beam transversely in the laboratory. it showed good potential for the experimental investigation of linear parametric system. therefore, experiments for the natural frequency, the response (both free and forced) spectra and frequency response characteristics of a cantilever beam under electromagnetic excitation, are, respectively, conducted to study the dynamic characteristics of linear parametrically excited system. the vibrational model of the cantilever beam system is established using the assumed mode method. theoretical results, related to the natural frequency, response spectra and external resonant condition, are presented to verify the experimental results. it is shown that the dynamic characteristics of linear time-periodic system do have some typical features, which differ distinctly from that of the linear time-invariant system.