Abstract
In this study, by utilizing the power generation characteristics of vibrated electret, a new passive type vibration velocity sensor was developed. In order to analyze the information on the vibration from measured time histories of voltage, a new electret electrode structure was proposed based on the numerical simulation. In constant amplitude vibration tests, the relationship between velocity, measured voltage and vibration frequency was clarified. As a result, the generated voltage and velocity have a linear relation-ship with a fixed angle that depends on the frequency, and the relationship between generated velocity per unit velocity and frequency was obtained as transfer function to convert voltage to velocity. For random vibrations, data processing method using the transfer function was proposed. Furthermore, due to the characteristics of the developed sensor, displacement and acceleration can be also obtained. Finally, the measurement on an actual bridge was conducted to examine the applicability of proposed sensors.
