The influence of electromagnetic actuators (EMAs) on the frequency response of a harmonically excited cantilever beam is investigated analytically, numerically and experimentally in this paper. Specifically, the intensity of the current generating the EMAs force is varied and its effect on the dynamic behavior of the system is analyzed. Analytical treatment based on perturbation analysis is performed on a simplified equation modeling the one mode vibration of the cantilever beam. Results indicated that EMAs produce a softening behavior in the system. Further, it is shown that as the current intensity of EMAs increases, the resonance curve shifts toward smaller values of frequency and the nonlinear characteristic of the system becomes softer. The analytical predictions have been verified numerically and confirmed experimentally using a test rig.

The control of vibroimpact dynamics of a single-sided Hertzian contact forced oscillator is investigated analytically and numerically in this paper. The control strategy is introduced via a fast excitation and attention is focused on the response near the primary resonance. The fast excitation is added to the basic harmonic force, either through a harmonic force applied from above, or via a harmonic base displacement added from bellow, or by considering the stiffness of the oscillator as a periodically and rapidly varying in time. The results reveal that the threshold of vibroimpact response initiated by jump phenomenon near the primary resonance can be shifted toward lower or higher frequencies of the slow dynamic system depending on the fast excitation taken into consideration. It was also shown that the most realistic and practical way for controlling the vibroimpact dynamics is the introduction of a fast harmonic base displacement.

The effect of a fast harmonic base displacement and of a fast periodically time varying stiffness on vibroimpact dynamics of a forced single-sided Hertzian contact oscillator is investigated analytically and numerically near sub- and superharmonic resonances of order 2. The study is carried out using averaging procedure over the fast dynamic and applying a perturbation analysis on the slow dynamic. The results show that a fast harmonic base displacement shifts the location of jumps, triggering the vibroimpact response, toward lower frequencies, while a fast periodically time-varying stiffness shifts the jumps toward higher frequencies. This result has been confirmed numerically for both sub- and superharmonic resonances of order 2. It is also demonstrated that the shift toward higher frequencies produced by a fast harmonic parametric stiffness is larger than that induced by a fast base displacement.

The effect of electromagnetic actuation (EMA) on the dynamic of a single-sided Hertzian contact forced oscillator is studied near primary and secondary resonances. Emphasis is put on the case where two symmetric EMAs are introduced, such that one is driven by a DC actuation and the other is actuated by AC actuation with a fast frequency. An averaging technique and a perturbation analysis are performed to obtain the frequency response of the system. It is shown that for appropriate values of AC, forced Hertzian contact systems are more likely to remain operating in the linear regime without the loss of contact near certain resonances.

Abstract. The effect of high-frequency AC electromagnetic actuation (EMA) on the dynamic behavior of a harmonically excited cantilever beam is analyzed in this paper. Analytical treatment based on perturbation analysis is performed on a simplified one degree of freedom equation modelling the first bending mode of the cantilever beam. The results show that under a certain specific condition relating the intensity of the fast AC to the displacement, the nonlinear characteristic of the system can be controled.