Design and initial validation of micro image strain sensing system based on digital microscope-camera

Abstract

Strain response is one of the most widely used methods for structural health monitoring because of its high accuracy in static and dynamic measurement. Although several sensing technologies have been developed for strain measurement, they need specialized equipment such as fiber Bragg grating interrogator, which is costly and cumbersome for general structures, especially for small infrastructures. Therefore, a micro image strain sensing (MISS) method was improved based on our previous preliminary study. The novelty of MISS sensor is that digital microscope camera is adopted instead of the combination of smartphone and microscope for long-term monitoring. Moreover, the micro image strain sensing system was developed on the basis of improved speeded-up robust features (SURF) algorithm. Experimental results showed that the strain measured by the micro image strain sensing system is consistent with that measured by the linear variable differential transformer, indicating that the system is stable and robust. This system has the advantages of low cost, high accuracy, and easy to operate. It does not need interrogators and can be used to measure strain quickly even for non-professionals. The proposed micro image strain sensing method will serve as a promising strain measuring alternative in the field of structural health monitoring.