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 multi-objective optimization challenges associated with sensor miniaturization and sensitivity enhancement, we developed a theoretical model and employed response surface methodology (RSM) combined with a multi-objective 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 20×20×20 mm³ and a mass of 41.47 g. Ultra-short small-diameter FBGs were packaged using a dual-point encapsulation technique. Experimental results indicated that the sensor presented natural frequencies of 1570 Hz (X-axis), 1600 Hz (Y-axis), and 1620 Hz (Z-axis), with corresponding sensitivities reaching 67.34 pm/G, 65.61 pm/G, and 63.48 pm/G, respectively. The operational flat frequency range 20 - 1000 Hz, with the cross-axis interference in non-operational 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 multi-degree-of-freedom measurements. With its compact size, high sensitivity, broad frequency range, electromagnetic immunity, and multi-point deployment capability, this sensor is highly applicable for multi-axis medium-to-high frequency vibration measurements in confined spaces within aerospace and mechanical equipment applications.