Name: KAIO FÁBIO DE OLIVEIRA SANTOS
Publication date: 25/09/2026
Advisor:
Name |
Role |
|---|---|
| ANSELMO FRIZERA NETO | Advisor |
Examining board:
| Name |
Role |
|---|---|
| ANSELMO FRIZERA NETO | Presidente |
| ARNALDO GOMES LEAL JUNIOR | Coorientador |
| JEAN CARLOS CARDOZO DA SILVA | Examinador Externo |
| LUIS GUSTAVO GIACON VILLANI | Examinador Externo |
Summary: Condition-based maintenance of rotating machinery relies on vibration measurement, and fiber Bragg grating (FBG) accelerometers are attractive for this task because they are immune to electromagnetic interference, can be multiplexed along a single fiber, and operate remotely from the acquisition unit. Their adoption is limited by three coupled constraints: sensitivity and natural frequency trade against each other, the grating responds to temperature as well as to strain, and compliant transducer frames admit transverse parasitic modes inside the operating band. This dissertation designs, optimizes, and experimentally validates an additively manufactured FBG accelerometer that addresses the three simultaneously. The architectures commonly found in the literature were cast into a common one-degree-of-freedom analytical framework and compared through NSGA-II multi-objective optimization; a hexagonal one reached between twelve and thirty times the sensitivity of its peers where the three Pareto fronts overlap in the comparison. Enhancements were developed on that topology: a push-pull configuration with two hexagonal stages on opposite faces of the inertial mass to cancel the thermal term while doubling the differential mechanical term and raising the natural frequency by 2 at fixed sensitivity, and a lateral leaf-spring reinforcement that suppresses the transverse parasitic modes at almost no cost on the Pareto front. A prototype was dimensioned at the high-frequency end of the front, printed in carbon-reinforced polyamide 11 by fused filament fabrication, and characterized on an electrodynamic shaker against a calibrated reference accelerometer. The measured resonance is 2340 Hz, within 7.5% of the finite element prediction, with a flat band reaching 855 Hz by a 1 dB criterion, a static sensitivity of 11.33 pm/g with an expanded uncertainty of 1.77 pm/g at k = 2, a noise floor of 89.58 mg RMS in band, and a figure of merit S · fn of 26.5 nm·Hz/g. The device is competitive on bandwidth and on manufacturability rather than on raw sensitivity, a consequence of the design point chosen on the trade-off. Thermal compensation was established analytically and remains to be verified experimentally.
