HYBRID ROTARY-TRANSLATIONAL ENERGY HARVESTER FOR MULTI-AXIS AMBIENT VIBRATIONS

A nonlinear electromagnetic energy harvester is presented which can generate power from translational vibrations in two directions and rotational excitations. Commonly, vibrational energy harvesters are designed to generate power from only translational ambient oscillations in a specific direction. The assumption of uni-axial ambient vibrations is too idealistic. Not only the direction of the base excitations typically change in time but also the rotational excitations are as common in oscillating machinery as the translational vibrations. The proposed energy harvester is inspired by the Automatic Generating System in Seiko watches. The moving element is a magnetic pendulum. When the pendulum moves in response to the base excitations the magnetic tip passes over electromagnetic coils, positioned in a circular array in the stator. The relative motion of the tip magnet and the coil generates electricity. The paper presents an analytical representative model for the energy harvesting system. The dynamics and energy generation of the energy harvester in response to four different excitation configurations are studied. It is demonstrated that in response to large excitations the system commonly undergoes period doubling bifurcations and occasionally undergoes chaos. The study paves the way to optimal design of the hybrid rotary translational energy harvesters.