Self-powered propeller rotary speed measurement with a piezo-electromagnetic energy harvester

Abstract The precise monitoring of propeller rotational speed is crucial for ensuring the navigation stability and motion control of autonomous underwater vehicles. Conventional speed sensors often rely on external power supplies, which limit their long-term deployment in underwater environments. To overcome this limitation, this study proposes a novel self-powered propeller speed measurement system based on a hybrid piezoelectric-electromagnetic energy harvester. The measurement system is composed of two distinct energy harvesting mechanisms: one based on the piezoelectric principle and the other on electromagnetic induction. The piezoelectric unit is used for sensing and detection, while the electromagnetic unit is used for energy harvesting and self-powering. This dual-functional integration enables the system to simultaneously extract energy from propeller rotation and generate speed-indicative electrical signals without external power. A theoretical model of this self-powered detection system was established, and simulation analysis was performed. Piezoelectric rectification and electromagnetic rectification circuits were designed, and the electrical energy of the self-powered measurement system was collected and stored. An experimental testing platform for a self-powered underwater propeller speed detection system was constructed and tested. Results show the maximum output power of the electromagnetic unit is 100.2 mW. Within the speed range of 0–360 r min −1 , the maximum relative error between the measured speed of the self-powered system and the reference speed provided by the servo motor is 1.3% at 210 r min −1 . What’s more, the designed self-powered system exhibits a linearity of 0.91%. The research results have important practical applications for achieving high-precision self-powered detection of underwater vehicle propellers.