Nihon Kikai Gakkai ronbunshu (Jan 2021)
Vibration control of self-excited system and forced self-excited system by dynamic vibration absorber
Abstract
It is desired that the forced self-excited vibrations of structures subjected to the vortex excitation and the long-period earthquake are quenched. Therefore, this paper deals with the vibration control of self-excited system and forced self-excited system using dynamic vibration absorber. Vibration quenching is researched using characteristic roots of the system and the entrained periodic solutions obtained by the shooting method. As a result of numerical calculation using the fact that the optimum vibration control of the self-excited vibration system can be performed by the theory that omits the nonlinear term of the damping term and considers only the linear term, following was made clear: At first increase the mass ratio of the dynamic vibration absorber with the increase of the negative damping coefficient. And adopt the several percent larger natural angular frequency ratio than the optimum vibration control value of forced vibration, and adopt the several tens of percent larger damping ratio than the optimum value of forced vibration, depending on the value of the negative damping coefficient. About the vibration quenching of forced self-excited vibration, following was made clear: (1) When the non-linear damping term, which is the cause of self-excited vibration, is small and the amplitude of force is also small, optimal control is approximately performed using the optimal values of the parameters for vibration quenching of forced vibration without damping. (2) When the amplitude of the forced force is large, the vibration quenching effect is reduced if the above mentioned approximate optimal values are used. The vibration quenching effect can be improved by using the smaller angular frequency ratio. (3) As the non-linear damping term increases, the optimal angular frequency ratio and optimal damping ratio of the dynamic absorber decrease.
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