Modal freeback control of tower structure using PVDF modal sensor and SMA/CFRP hybrid moment actuator

Low frequency modes of tower structure generated by a strong wind or by an earthquake cause deterioration or a collapse of structure because stress concentration happens at the root of structure. High frequency modes, on the other hand, are often disregarded because they can be damped immediately by themselves. The objective of present report is to pick up and to suppress specific vibration modes only which bring about such problems, it means here low frequency modes, among all of generated vibration modes in structure. First of all, a design of modal sensor made of PVDF film is proposed to pick up only low frequency modes by using FEM analysis. Then, an application method of SMA/CFRP hybrid actuator, which can generate great force in a range of low frequency, is explained. By using these PVDF modal sensor and SMA moment actuator, vibration model can be simplified by reducing to low dimensions. Consequently, modal control system, which suppresses only low frequency vibration modes, is constructed. At end of the present paper, effect of this control system is demonstrated experimentally.