Development and Implementation of a Laser–Camera–UAV System to Measure Total Dynamic Transverse Displacement

Abstract

Railroad bridge inspectors are interested in measuring the maximum total transverse displacement of railroad bridges under trains, but these values are generally not easy to obtain in the field without sensors. Engineers use LVDTs, analog accelerometers, or wireless smart sensors (WSS). However, these sensors need to be attached to the bridge prior to the train-crossing event, which requires time, costs money, and is unsafe for engineers. This paper describes the design of a new sensor-equipped, low-cost unmanned aerial vehicle (UAV) system that enables the safe, cost-efficient, and noncontact total transverse displacements measurement of railroad bridges. The new system integrates laser and camera measurements from a UAV flying near the moving structure. The design and assembly of the new system is followed by methodology, field experiment, and results. The authors compared the estimations of the new system with ground-truth data obtained using an LVDT to quantify the capabilities of the new system. The results support the value of the proposed method to measure noncontact railroad bridge displacements in the field.