... tuning range, Proceedings PowerMEMS 2 010, pp. 207-211, Leuven, Belgium, December 1-3, 2 010 Sustainable Energy Harvesting Technologies – Past, Present and Future 62 Fig. 6. Magnetic circuit ... the possible applications of the vibrational energy harvester. A prototype of the Sustainable Energy Harvesting Technologies – Past, Present and Future 661.4.2 Four magnets vibrational ... frequencies and resonance occurs when the system’s natural frequency matches the frequency of oscillation of the external force. Sustainable Energy Harvesting Technologies – Past, Present and Future...