Halbach-enhanced variable reluctance energy harvesting for self-powered condition monitoring

Wireless condition monitoring of critical rotating components, such as shafts, bearings, and gears, can be efficiently powered by energy harvesting technologies, supporting improved operation and maintenance. However, conventional energy harvesters struggle to meet the energy demands of wireless condition monitoring operating at low rotational speeds, severely limiting their practical deployment in industrial applications. To address this challenge, this paper proposes a new Halbach-enhanced variable reluctance energy harvester (HE-VREH) to improve the power density under low-speed conditions. A theoretical model based on magnetic circuit analysis is established to predict the voltage response of the proposed HE-VREH, while finite element simulations are performed to analyze the magnetic flux distribution and benchmark its performance against existing variable reluctance harvesters. Moreover, experimental measurements validate the theoretical model in predicting the output performance. The experimental results indicate that the proposed HE-VREH generates a power of 210.32 mW at a rotational speed of 55 rpm, achieving a normalized power density of 1.83 mW/(cm³∙Hz²). Furthermore, an autonomous wireless sensing system powered by the HE-VREH is able to successfully capture vibration and torque signals during rotation. The combination of detailed modelling and experimental validation confirms the potential of the novel HE-VREH to enable self-powered condition monitoring in industrial rotating machinery, thereby bridging the critical gap between energy harvesting efficiency and low-speed operational requirements.