Active seismic sensor using digital control system and optimal feedback controller

抄録

One of the authors had presented a novel seismic sensor using feedback control to extend the measurable frequency range to such lower frequency. An ordinary seismic sensor utilizes a mass-spring-damper system possessing lower natural frequency so that relative motion of the mass over the natural frequency domain can be measured as absolute motion of the ground. Therefore, if the natural frequency is lower, the measurable range of the seismic sensor is wider. To realize lower natural frequency, one of the authors introduced feedback controller and output shaping. According to this idea, as low as 0.1 Hz of ground motion can be measured. However, a digital feedback controller using classical control theory in the previous study had problems such as limitation of measurement range, and mismatch of the measurement signal in large amplitude vibration. In order to improve measurement performance, we aim to introduce the controller with modern control theory. This control theory can obtain more accurate measurement signal because it can utilize state variables. To measure the relative displacement of the sensor in order to do modern control with two state variables, one of the authors introduced a photo reflector in a previous study. In this study, the authors designed a controller based on modern control theory and simulated the sensor using MATLAB when applying the control. We also applied this controller to the sensor and did an experiment to confirm its performance. From these results, the performances of simulation and experiment were confirmed good agreement. Therefore, it was confirmed that the sensor could be controlled by the controller using modern control theory.