On-line frequency estimation and adaptive vibration control of composite structures with delaminations

An on-line natural frequency estimation method and an adaptive vibration control of composite beams are investigated. Once delaminations occur in the composite structures, dynamic characteristics of the structures are changed including the decreases of natural frequencies due to the defected stiffness. In this paper, a real-time frequency estimation method is proposed to detect frequency shifts of the specimen. In addition, an on-line adaptive controller, named Adaptive Positive Position Feedback (APPF), is suggested. Glass/Epoxy composite beams with delaminations at different locations are manufactured and surface bonded piezoceramic actuator is used as an actuator. It is found that the estimated frequencies converge to real ones, and successful multi-mode vibration suppression is achieved using the proposed on-line adaptive controller.