In this paper, the feasibility of an active vibration control scheme using Fiber Bragg Grating (FBG) sensors and
piezoelectric (PZT) actuators for vibration suppression of an aluminum plate is investigated. Four FBGs have been
bonded to the structure below the same number of PZT actuators in co-located configuration. A Proportional-Derivative
controller has been used to generate the command signals required to drive the actuators. Preliminary results from
"closed loop" configuration tests are reported showing up to 17 dB of noise reduction at 80 Hz.
This paper presents the first results on the use of the pre-stress to improve the performance of a magnetic field sensor
based on a Terfenol-Fiber Bragg Grating integrated device. Indeed, since the pre-stress modifies the response of the
magnetostrictive material, this should allow to fit the performances of the sensor to different operative conditions or to
exploit also the stress as a control variable to optimize the design of the sensor.
In this work, the experimental demonstration of fiber Bragg grating based sensors as magnetic transducers is reported. Up to now, FBGs based magnetic sensors have been proposed by using Terfenol, metallic alloy with a giant magnetostriction coefficient. Here, a novel configuration is proposed employing a new class of magnetic materials, Magnetic Shape Memory alloys (MSMs), instead of Terfenol. This class of material, with a very giant magnetostriction coefficient, changes its shape when magnetic fields are applied. High strain values, up to 10 percent can be obtained with fast response times (less than 1 ms). A fiber Bragg grating has been bonded on a MSM sample and sensor characterization has been carried out. Experimental results and the comparison with Terfenol based FBGs sensors performances are reported, showing, for MSM, a sensitivity expressed as (▵λ<sub>B</sub>/λ<sub>B</sub>)/( ▵H/H<sub>m</sub>) of 1.1e-4.
An aluminum prototype of the AMICA (Astro Mapper for Instrument Check of Attitude) Star Tracker Support (ASTS) of the AMS_02 (Alpha Magnetic Spectrometer) space experiment has been instrumented with Fiber Bragg Gratings (FBGs). In this work the use of FBGs to perform dynamic tests on the ASTS prototype is reported. The excitation has been provided by an instrumented impact hammer, the mechanical response of the structure has been obtained by bonded FBGs and accelerometers. All time histories have been recorded, transformed in the frequency domain to retrieve Frequency Response Functions (FRFs)-accelerometer responses- and Strain Frequency Response Functions (SFRFs) -FBG responses-, both providing resonant frequencies and displacements (strain) shapes of the ASTS. Numerical simulations of this structure have been performed to predict its resonant frequencies and vibrational displacement (strain) shapes. Experimental results demonstrate the capability of FBGs to perform in situ experimental modal analysis as confirmed by the comparison of the optical response with the accelerometers one and the good agreement with the numerical analysis.