Generation of quasi-resonance by variable damping

Abstract

This paper proposes a new method to generate a quasi-resonance by variable damping in a base-excited vibration system. In general, the applications of variable damping are to dissipate energy of the vibration system and to reduce the amplitude as soon as possible. Our purpose of the application is not decrease but increase of the amplitude of the vibration system. In this paper, a simple single-degree-of-freedom base excited model with a variable damper is considered. The coefficient of the variable damper is changed like a sine wave, i.e. parametric excitation which of the frequency can be freely chosen. The damping force generated by the variable damper is equivalent to a product at the variable coefficient and the relative velocity of the system between the base and the mass. By multiplying the input sinusoidal wave from the base excitation by the frequency controllable sinusoidal wave of the variable damper, new vibration that has another frequency besides the input frequency arises. Therefore, the controllable oscillation of the damping coefficient in a suitable frequency can generate new vibration that has the same frequency as the natural frequency of the vibration system. As a result, the amplitude of the vibration system increases because of a phenomenon that is similar to common resonance. In this paper, we clarify the facts on the growth of the amplitude by the proposed method in numerical analysis.