Nonlinear electromagnetic generators with polymeric materials for power harvesting from vibrations

The power consumption reduction of electronic devices has allowed supplying them through the harvesting and subsequent conversion of electrical energy that is present in different forms in the measurement environment. Mechanical energy from vibrations is the most common energy source. In the proposed nonlinear electromagnetic generators, the vibrations generate an oscillatory movement of a planar inductor placed in a constant magnetic field, thereby generating a voltage on the coil due to the change in magnetic flux. In the case of low-frequency vibrations, it is necessary to consider two conflicting demands: firstly, in the hypothesis of linearity, the resonant frequency reduction requires an increase in mass and softness of the spring, against the size reduction requires structural stiffening and an obvious reduction in mass. The generator considers a proposed nonlinear elastic behavior of the suspension on which the inductor is placed, improving the system efficiency than the linear case, and especially by introducing behaviors that are not intuitively predictable and potentially exploitable for the proposed purpose. A mathematical model is used to study the nonlinear behaviors; the model is referred to a mass-spring-damper system with harmonic force support. The retraction force is nonlinear by adding a cubic term, and damping is proportional to the speed with an electrical and mechanical component. The generators are built and tested using a specially designed experimental setup. The working frequencies of the generators are between 25–40 Hz. The experimental results are compared with results obtained by the mathematical model, getting a good match.