Abstract
This paper reports new results for developing absolute displacement sensor in order to measure a long period and large magnitude. Measuring of the absolute displacement of vibration objects, the natural frequency of sensor must be lower than the dominant frequency of the object. Therefore, it is difficult to measure a low frequency vibration below 1 Hz using conventional displacement sensors. In order to be lower the natural frequency, the sensor with the low natural frequency is realized by using feedback control. It has been demonstrated that a developed sensor has a detecting range from about 0.2 Hz to 10Hz for absolute displacement. In addition, the measurement displacement amplitude has been expanded to about 700 times. Moreover, by using the second order lag compensator measuring lower frequency range is expanded to 0.1 Hz.
