Desenvolvimento de modelos de sensoriamento por fibra óptica para detecção e medição de peso de veículos ferroviários e rodoviários

Abstract

This thesis presents the development, implementation, and experimental validation of two fiber-optic sensing systems for transportation monitoring applications. The first system consists of a vibration sensor based on the single-mode–multimode–single-mode (SMS) configuration, proposed for detecting the passage of railway vehicles through the vibrations induced in the rail. The second system corresponds to a Weigh-In-Motion (WIM) system based on fiber Bragg gratings (FBG), designed for monitoring vehicular loads under continuous traffic conditions. For the SMS sensor, laboratory experiments and supervised field tests were conducted using a light vehicle running on rails, a freight train, and a maintenance train. The results demonstrated the feasibility of detecting railway events through the analysis of signal variability, as well as the presence of spectral signatures associated with different types of vehicles. The spectral energy at low frequencies, that is, the amount of signal energy distributed over the lower-frequency components, showed an approximately linear correlation with vehicle weight, highlighting the potential of the system for future applications in railway characterization and classification. For the FBG-based WIM system, an instrumented aluminum mechanical structure was developed and integrated with an opto-electronic acquisition system and silicone damping elements. The experimental validation included static laboratory tests using a universal testing machine and field tests with real vehicles. The results showed consistent behavior in the static tests, enabling system calibration and the evaluation of models for load estimation. In the dynamic free-flow tests, although accurate estimation of the total vehicle weight in motion still requires further improvements, the recorded signals demonstrated sensitivity to axle passages and indicated that the measured signals contain relevant physical information for the future development of the system. Overall, the results confirm the potential of fiber-optic sensors for applications in transportation environments, highlighting their electromagnetic immunity, versatility, sensitivity, and capability for integration into intelligent monitoring systems.