Towards airborne laser Doppler vibrometry for structural health monitoring of large and curved structures

Laser Doppler vibrometry is an important sensing technology for many structural health monitoring (SHM) methods, such as modal analysis. However, when it comes to large civil structures, for example historic structures and bridges, the applicability of laser Doppler vibrometry is significantly constrained by inaccessible remote surfaces. Some of these surfaces are fully inaccessible to a ground-mounted laser Doppler vibrometer (LDV), while others are partially inaccessible, and measurements are only possible for low incident angles. Consequently, LDV measurements are either impossible or have a weak signal strength. In this study, the concept of constructing an airborne LDV for SHM is explored, including the examination of a recently developed mechanism, the partially airborne LDV, comprising a reflective mirror attached to a drone. Preliminary proof of concept laboratory tests have been successfully conducted using two different set-ups and drone models.