フィードバック制御を用いる絶対変位計に対する出力整形による計測帯域の拡大

Abstract

One of the authors had proposed a new type of active seismometer measuring such vibration possessing long period and wide dynamic range. In order to lower the natural frequency of the sensor and expand the detectable amplitude, the sensor with the lower natural frequency and lower sensitivity is realized by using feedback control. Based on this idea, authors have been developing an experimental active seismometer with feedback controller. In the previous studies, its performance is reported that the measureable lowest frequency is extended from 4.1 Hz to 0.56 Hz, while the acceptable vibration amplitude is expanded to 141 times bigger than original sensor stroke (or the sensitivity is reduced 43 dB). However, due to the limit of feedback gain, further improvement of the dynamical property solely by using feedback control is not hopeful. In this study, to compensate phase-delay of the sensor output and to expand the dynamic range, third order phase-lag compensator is added to shape physically measured output. Feedback controller and third order phase-lag compensator are designed as analog circuit and built into the sensor. Frequency transfer function of the sensor output is identified through shaking table test. It has been demonstrated that the detectable frequency range of the sensor is extended to 0.15 Hz.