| 摘要 |
PROBLEM TO BE SOLVED: To extract only the specified arbitrary vibration mode signal components from among vibration signals of a beam structure in which many vibration modes are superposed to vibrate complicatedly, in order to constitute a simple and sure vibration control system. SOLUTION: Monochromatic light emitted from a laser beam source 4 is coupled to a single mode fiber 6 by a condenser lens 5 to be transmitted to a two-mode optical fiber sensor 2 attached to a beam structure 1 via splice tool 7. A dual-mode optical fiber bonded to a surface and a reverse face of a beam alternately in order to correspond to positive and negative codes of a twice differentiated value related to the position of a vibration mode intended to be extracted in the beam structure 1. A light intensity signal provided from an emitting end of the dual-mode optical fiber is converted into an electric signal of monovibration mode required for control by a photodetector 8, a by-pass filter 9 and a signal amplifier 10.
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