No abstract

In our previous works, we presented a method to increase the harvested energy from vibrations using a piezoelectric cantilever and to increase the frequency range of operation by introducing bistability with the use of magnetic repulsion. However, for small excitations, the cantilever may not be able to overcome the magnetic repulsive force but vibrate at one of its two equilibrium positions with reduced amplitude. This work introduces a method of increasing the range of excitations over which the operation remains bistable. This is achieved by spring loading one of the magnets, previously on a fixed support, allowing motion in one dimension only, toward and away from the cantilever in the horizontal plane. Configured so, as the cantilever moves toward this magnet, the repulsion due to the cantilever-mounted magnet pushes the spring-loaded magnet away, increasing distance, and thus, reducing magnetic force between them, required to be overcome by external excitations for bistable operation. Similarly, as the cantilever moves away, the spring pushes the magnet closer to the cantilever-mounted magnet, increasing vibration amplitude. Thus, the spring introduces a negative feedback which favors bistable operation over an increased range of excitations. This completely mechanical method requires no additional energy cost. Peak power gains of up to 90 and a decrease in excitation voltage of up to 60% were observed over the fixed magnet.

This paper presents ambient mechanical vibrations as an alternative source for energy harvesting, especially beneficial where alternatives such as light, wind, biomass and thermal energy are limited, e.g., powering underground sensors. Transduction of ambient kinetic energy, e.g., the vibrations from thunder and field work, into electrical energy using piezoelectric generators has been investigated, utilizing a nonlinear bistable broadband piezoelectric harvester. A new model for the bistable piezoelectric harvester is suggested based on the standard Butterworth van Dyke model and its validity demonstrated through simulations. For efficient extraction of the transduced energy, we employ synchronous charge extraction (SCE) and parallel synchronized switch harvesting on inductor (SSHI). The switching in these circuits is implemented using a fully self propelled, low-power electronic breaker circuit, capable of detecting extrema in the input to perform switching. The power outputs from simulation of the bistable harvester have been presented, with the SCE and parallel SSHI providing respective average outputs of 78.51lW and 1251lW for a sinusoidal input of 0.326N at 10Hz applied to a 69.1 x 16.8 x 0.64 mm 3 cantilever (piezoelectric dimensions 35.56 x 14.48 x 0.2 mm 3 ). This shows significant gains over the harvested power reported in literature.

No abstract

No abstract