Realization of a LoRa-based piezoelectric self-powered wireless monitoring system for steel spring floating slab tracks

Self-powered wireless monitoring technology demonstrates strong potential for enabling distributed passive monitoring with long-term reliability in railway infrastructure, significantly enhancing intelligent operation and maintenance of railway systems. Previous studies have preliminarily verified the feasibility of a LoRa-based piezoelectric self-powered wireless monitoring system (P-SPWMS) for railway bridge applications. However, existing research primarily focused on bridge acceleration-driven resonant-type dynamic-magnified piezoelectric energy harvesters (D-M PEHs), which are unsuitable for displacement-driven PEHs in steel-spring floating slab tracks due to their lower operating frequencies (below 10 Hz). To address this limitation, this study develops and implements a LoRa-based P-SPWMS specifically for steel spring floating slab tracks. The system incorporates a novel floating slab displacement-driven high-power piezoelectric energy harvester (HP-PEH), whose performance is comprehensively evaluated through both experimental testing and electrical simulations under harmonic displacements and a special floating slab displacement. An improved energy management circuit (EMC) based on an AP64500 chip featuring reduced threshold voltages is designed to complement the proposed HP-PEH. Five trackside wireless sensors are employed to assess system performance under two distinct floating slab displacement scenarios in laboratory tests. Furthermore, a fatigue test is conducted to evaluate the long-term service stability of the HP-PEH. Experimental results show that the HP-PEH can reliably power each individual one of the five wireless sensors multiple times per day, providing critical technical support for intelligent monitoring and maintenance of steel spring floating slab tracks in rail transit systems. The HP-PEH can generate sufficient energy to illuminate a circuit board with 43 LEDs, indicating potential applications in emergency tunnel lighting during train operations. In addition, the HP-PEH exhibits good fatigue resistance, ensuring long-term service durability.