Results for the design and testing of an electromagnetic device that converts ambient mechanical vibration into electricity are presented. The design of the device is based on an L-shaped beam structure which is tuned so that the first two natural frequencies have a near two-to-one ratio which is referred to as an internal resonance or autoparametic condition. It is shown that in contrast to single degree-of-freedom, linear-dynamics-based vibration harvesters which convert energy in a very narrow frequency band the prototype can generate power over an extended frequency range when subject to harmonic, base displacement excitation.

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