Abstract
We have proposed a first-order differential type seismic displacement sensor for vibration control of anti-vibration apparatuses. This sensor is ideal for use in Direct Acceleration, Velocity and Displacement FeedBack (DAVDFB), because absolute acceleration, velocity and displacement signals are simultaneously detected. We can avoid drift problems due to integral operators which are critical in a conventional control scheme with commercial accelerometers. However, detection bandwidth of the proposed sensor is narrow to control leading-edge anti-vibration apparatuses. This paper presents bandwidth expansion in low frequency region with hybrid detector system. Since the bandwidth is limited owing to high frequency dynamics, a cause of the dynamics is determined by root locus analysis. In this process, we reveal some features of the proposed sensor comparing with second-order differential type seismic displacement sensor. As a result, the bandwidth is expanded by detecting back electromotive forces from not only a calibration coil but also a forcer coil.
