A two-degree-of-freedom nonlinear electromagnetic energy harvester in rotational motion

Electromagnetic energy harvesting has sparked the interest of researchers due to its promising potential in powering miniaturized electronic systems and wireless sensor networks. This paper focuses on a two-degree-of-freedom nonlinear electromagnetic energy harvester (2DOF-NEMEH) using a magnetic levitation architecture in rotational motion. The residual magnetic flux density is identified by the finite element method and gradient descent method, enabling a more precise description of the model. A dynamic model, accounting for the centrifugal force and the Stribeck friction in rotational motion, is established and validated by an agreement between experimental and numerical results. The mechanisms that can respectively enhance the energy output performance of the 2DOF-NEMEH in two different installation configurations are studied: One is to enhance the maximum output power through the negative damping of the stick–slip phenomenon for low-speed rotational motion, while the other is to broaden the operating frequency band through the combined effect of centrifugal force and 2DOF arrangement. The centrifugal stiffening effect and sudden-drop phenomenon are explored. Ultimately, optimization of the 2DOF-NEMEH achieved a maximum average output power of 4.6 mW and a wide operating frequency band spanning 0 to 600 rpm. Power supply tests for sensors are conducted on the optimized 2DOF-NEMEH, confirming its application potential.