Nonlinear testing and models comparison of magneto-mechanical energy scavengers

his paper describes modeling and experimental testing of a magneto-mechanical energy scavenger. The examined device is a vibration-driven linear generator, where the translator is constituted by a permanent magnet and the stator by two axial coils. Two fixed permanent magnets act on the translator as a nonlinear hardening spring. Analytical, numerical and empirical models of the elastic force, due to the interaction between moving and fixed magnets, are described and discussed. Two experimental test rigs are presented to validate the analytical and numerical results: the first one is a tunable rig to measure the repulsive force between magnets with different dimensions, volume ratios and configurations; the second one is a parametric energy scavenger which aims to validate linearized dynamic properties, non linear magnetic effects and dissipative phenomena with a simplified tunable electric load coupled to it. Experimental tests are performed to validate the models by varying source characteristics, moving and fixed magnet sizes, stroke and clearance. Simulations and tests are also performed to verify the scalability of the device and to relate the output power with the size of the moving magnet.