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Development of a Seismometer-Type Absolute Displacement Sensor Aimed at Detecting Earthquake Waves with a Large Magnitude and Long Period



Author(s)

Kazuto Seto1, Yuichi Iwasaki2, Akihiko Itoh3 and Ikuo Shimoda4

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DOI:10.17265/1934-7359/2012.06.010

1. Seto-Vibration Control Laboratory, Kanagawa 240-0116, Japan
2. Engineering and Design Department，Oiles Co., Tochigi 326-0327, Japan
3. Research and Development Department，Oiles Co., Kanagawa 252-0811, Japan
4. Oiles Co., Tokyo 108-0075, Japan

This paper proposes a novel seismometer-type absolute displacement sensor aimed at detecting earthquake waves with a large magnitude and long period. However, since the measuring range of the displacement sensor is higher than its natural frequency, it is difficult to detect low frequency vibrations below 1 Hz using a conventional a seismic-type displacement sensor. In order to provide an absolute displacement detection which is capable of lowering the natural frequency and enlarging the detectable amplitude without causing structural defects, the relative signals of displacement, velocity, and acceleration between a detected object and the auxiliary mass of the sensor are fed back into the sensor. In addition, phase lag compensation is inserted to adjust phase angles, which are of a frequency of 1 Hz. According to simulation results, a detection range from 0.1 Hz to 50 Hz is expected. It has been demonstrated that the developed sensor with a small size and light weight has a detection range of from 0.5 Hz to 50 Hz for absolute displacement and velocity. As an additional advantage, the measurement displacement amplitude has been expanded to about 20 dB. This sensor is available to use for the active control of flexible structures like high rise buildings using the LQ control method.

Vibration, displacement sensor, earthquake wave, measurement, structural control.