Development of a Compact Triaxial FBG Vibration Sensor for Medium-High Frequency Applications via Multiobjective Optimization Design

This study presents a miniature triaxial fiber Bragg grating (FBG) vibration sensor incorporating a novel elliptical guide-angle hybrid flexure hinge structure for stepper motor vibration monitoring. To tackle the multiobjective optimization challenges associated with sensor miniaturization and sensitivity enhancement, we developed a theoretical model and employed response surface methodology (RSM) combined with a multiobjective genetic algorithm (MOGA) for parametric optimization. The validity of the proposed design was verified by finite-element analysis (FEA) using ANSYS, through modal and harmonic response simulations. The sensor comprises three orthogonal assembled identical modules, achieving high spatial efficiency with compact dimensions of $20\times 20\times 20$ mm3 and a mass of 41.47 g. Ultrashort small-diameter FBGs were packaged using a dual-point encapsulation technique. The experimental results indicated that the sensor presented natural frequencies of 1570 (X-axis), 1600 (Y-axis), and 1620 (Z-axis) Hz, with corresponding sensitivities reaching 67.34, 65.61, and 63.48 pm/G, respectively. The operational flat frequency range is 20–1000 Hz, with the cross-axis interference in nonoperational axes below 4% of the primary axis. Real-time triaxial vibration monitoring of a stepper motor under varying conditions confirmed the sensor’s reliability and consistency in multidegree-of-freedom measurements. With its compact size, high sensitivity, broad frequency range, electromagnetic immunity, and multipoint deployment capability, this sensor is highly applicable for multiaxis medium-to-high frequency vibration measurements in confined spaces within aerospace and mechanical equipment applications.