Abstract
The paper aims to determine and analyse the frequency characteristics of an electromechanical vibration energy harvesting converter that comprises of a metal cantilever-beam spring driving a linear-motion permanent-magnet generator with a single-phase cored armature winding. The nonlinear parametric resonance phenomenon is analysed that the system exhibits due to action of the electromagnetic forces developed by the generator. In order to determine the steady-state frequency characteristics of the system a 1-D complex quasi-dynamic structural finite element model is coupled with 2-D magnetostatic finite element and circuit models. The nonlinearity and electric loading are taken into account. The region of feasible operation is determined involving physical limitations of the system that result from the assumed system topology and physical properties of materials used. The observations on bistability of the frequency characteristics are carried out. The results show that the converter should operate loaded due to risk of spring devastation at the bistable operation point. The quasi-optimal value of loading resistance providing maximum power at average value of the external excitation force is determined. The considerations are supported by laboratory experiments.