Wireless Telemetry for Characterization and Design of In-tire Piezoelectric Energy Harvesting Systems

The design of new a generation of smart tyre sensors directly powered by tyre motion, requires accurate information about electrical quantities related to electromechanical energy harvesters in realistic operating conditions. Transducers and circuits are not accessible inside tyres, and it is difficult to predict theoretically or numerically their behaviour. This paper presents a characterization methodology for energy harvesters in tyres based on wireless telemetry and on a series of specific measurements performed in an industrial-grade tyre test machine. A Wi-Fi modular telemetry platform is designed for acquiring inside tyres, at up to 14 kSa/s, open-circuit voltages up to ±160 V, and short-circuit currents up to ±18 mA, from piezoelectric transducers. A power estimation technique is executed locally to extract static power transfer characteristics. Measurements were performed in real-world conditions on commercial tyres in an industrial drum test machine operated at controlled speeds up to 40 km/h and axial loads up to 3 kN. Among its contributions, the paper analyzes the in-tyre behaviour of piezoelectric harvesters in terms of voltage, current, and power, and reports reference data from a relevant test environment to support power converter circuit design. To characterize joint in-tyre and energy-autonomous operation of piezoelectric transducers, power management circuits, and tyre sensors, fully functional electronic systems are validated on-field by the proposed telemetry platform. Validated circuits include passive rectifiers and synchronous electric charge extractors.