Modal feedback 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 occur deterioration or a collapse of structure because stress concentration happens at the root of structure. High frequency modes, on the other hand, are often possible to be disregarded because they can be damped immediately. In general, all vibration modes which are generated in the structure are tried to be suppressed when it is said as 'vibration control'. There remind, however, a lot of problems to realize a stable control in this case. The object of present paper is a pick up and a suppression of specific vibration modes which occur 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 separately by using FEM analysis. Then, an applied method of SMA/CFRP hybrid actuator, which can generate great force in a field of low frequency, is explained. By using these PVDF modal sensor and SMA moment actuator, vibration model can be simplified by means of modification to low dimensions. Consequently, modal control system, which suppresses only low frequency vibration modes, is constructed. At the end of the present paper, effect of this control system is demonstrated experimentally.