The objective of this work is to design cantilever beams possessing close vibration modes to enable harvesting energy from variable frequency sources of base motion. In this context, the geometry of two-dimensional cantilever beams is designed to obtain closely spaced harvestable modes of vibration. A number of internal slits are made inside the beam, whose outer contour and mass distribution are altered in such a way to obtain the desired frequency spacing. The beam carries two permanent magnets that oscillate past stationary pickup coils in order to convert the mechanical motion into electric power. Optimum design results of the shape and geometrical parameters of the system are presented towards controlling the natural frequencies, their spacing and the output power. Simulations of the system dynamics are supported by experimental validation.

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