Design and Analysis of Micro-Vibration Isolation System for Digital Image Correlation System-Based Structural Health Monitoring

Monitoring and analyzing the conditions of aging aerospace or civil structures such as aircrafts, bridges, and buildings are essential to verify structural integrity. The assessment of structural properties and dynamic characteristics of such systems are important to ensure long-term reliability and to determine the right time for component repair or replacement. Recently, improvement in camera technology and image-processing algorithms has made advanced non-contact full-field measurement techniques, such as the digital image correlation method, appealing for non-destructive evaluation and structural health monitoring. With increasing demands for better image quality and noise reduction from external sources, the stability requirements of camera systems for capturing are becoming more rigorous. To reduce the influence of camera micro-vibration on image quality, vibration isolation of the whole camera system must be considered. Therefore, a method to design and optimize a vibration isolation system needs to be developed. This study presents the engineering analysis and testing of a low-cost vibration isolator specifically aimed at vertical high-frequency motion. The device works on the principle of displacement transmissibility reduction by the use of a wave spring and specially designed brackets. The base features a threaded aperture to allow leveling adjustment of the platform. The isolator is fixed on an electromechanical shaker and excited by a swept-sine signal from 0 to 100 Hz with a small sweep rate. We measured the vibration of isolator by two laser sensors to obtain the transmissibility curve during its operation. As a result, the isolator filters out a broad band of input vibration frequencies and ensures a constant level of vibration transmission reduction in the vertical direction. The isolator features a 10 Hz vertical resonance frequency and begins isolating at 13 Hz. The proposed model is stable and performs sufficiently to eliminate 90% of vibration noise, which satisfies the requirement for a high-speed camera system on the ground.