In this study, the Genetic Algorithm (GA) was used to search the 4 modes filter frequencies to be applied to the multiple Positive Position Feedback (PPF) controller. The PPF technique, which makes use of generalized displacement measurements to maximize damping in a specific mode effectively and accomplish vibration suppression was employed as control scheme. However it is necessary to tune the filter frequency of the controller to the structural resonance prior to compensator design. Another disadvantage in the multi mode PPF control is that the lower mode natural frequency is shifted to the low-ward as the effect of the higher mode control by PPF controller. To minimize the effect of frequency shift and search the optimal filter frequencies for the multiple modes PPF controller, the GA was applied. The generally used fitness function of the GA in low modes PPF control, the square sum of sensor voltage output hardly distinguishes the definite difference in higher modes. Instead of it, in this study, the GA with the fitness function as the power spectrum information was performed. As a result of GA algorithm with this fitness function, the optimal filter frequencies of higher modes were found successfully.
An approach has been developed for real-time vibration monitoring of a composite cantilever beam. The fiber Bragg grating (FBG) sensor has an advantage to be embedded or bonded to the structure compared with other sensors such as piezoelectric sensor or strain gage, thus allowing the measurement of parameters like strain and temperature. In this paper the vibration sensor system with a FBG embedded in a composite smart structure is proposed. This system can assort vibration direction and sensing vibration amplitude just by measuring output voltage. The sensing resolution is decided by the slope of the filter used in the system.