Vibration and Shape Control in Opto-mechanical Systems Using Distributed Fiber-optic Bragg Grating Sensors

High-precision opto-mechanical systems are characterized by significant interactions between structural dynamics and optics. Novel sensing techniques for the vibration and shape control of such structures are investigated. Owing to the number of necessary sensors and the required precision, fiber-optic Bragg grating (FBG) sensors could be an attractive option for this task. They allow the simultaneous measurement of strain at many locations in a structure. Many FBG sensor systems provide high precision, but their delay time and maximum acquisition frequency makes them difficult to use for vibration control purposes. Therefore, a novel multi-channel FBG sensor system was developed using a position sensitive detector for the wavelength interrogation which has much less delay time than a charge coupled device-based system and a theoretical maximum bandwidth of over 300 kHz. This system was tested for high-precision static strain measurements for shape control applications at low frequencies in an experimental test rig (< 0.3 μm/m) as well as for high-frequency strain measurements of more than 10 kHz. Its application potential for shape and vibration control application was demonstrated experimentally as well as its applicability to modal analysis. This could be an interesting alternative to the use of piezo-strain sensors in structural control applications where high frequencies are needed, as well as an alternative for shape control where high-resolution strain measurements are desirable.