A Low-Cost Robotic Camera System for Accurate Collection of Structural Response

Abstract

Vision-based technologies are becoming ubiquitous when considering sensing systems for measuring the response of structures. Availability of proprietary camera systems has opened up the scope for many bridge monitoring projects. Even though structural response can be measured at high accuracies when analyzing target motions, the main limitations to achieving even better results are camera costs and image resolution. Conventional camera systems capture either the entire structure or large/small part of it. This study introduces a low-cost robotic camera system (RCS) for accurate measurement collection of structural response. The RCS automatically captures images of parts of a structure under loading, therefore, (i) giving a higher pixel density than conventional cameras capturing the entire structure, thus allowing for greater measurement accuracy, and (ii) capturing multiple parts of the structure. The proposed camera system consists of a modified action camera with a zoom lens, a robotic mechanism for camera rotation, and open-source software which enables wireless communication. A data processing strategy, together with image processing techniques, is introduced and explained. A laboratory beam subjected to static loading serves to evaluate the performance of the RCS. The response of the beam is also monitored with contact sensors and calculated from images captured with a smartphone. The RCS provides accurate response measurements. Such camera systems could be employed for long-term bridge monitoring, in which strains are collected at strategic locations, and response time-histories are formed for further analysis.