the zero deflection equilibrium is stable and the system is a “nonlinear monostable oscillator” coupled to the piezoelectric and electromagnetic circuits. If the tip magnet is close to the base the repelling force between the magnets, which forces the tip away from the zero deflection, becomes significant. The equilibrium will be unstable but there will be two stable equilibriums on the left and right side of zero deflection ( ). In this situation the system is “nonlinear bi-stable oscillator” coupled to the piezoelectric and electromagnetic circuits. The nonlinear vibrations of the nonlinear bi-stable oscillator is discussed in section 0. Fig. 2: The transduction element Fabrication and testing procedure The beam element in the hybrid harvester is a bimorph where the substrate is a 152.4 X 25.4 X 0.635 mm spring steel beam. There are two QP10n Mide’ QuickPacks placed on the sides of the beam. For proper clamping of the beam part of the piezoelectric patches and the substrate are clamped. The effective length of the substrate outside the clamp is 127 mm. The first 38.1 mm of the beam is covered on both sides by the Quickpacks. The blue electromagnetic coils illustrated in Fig. 2 are modified small transformers. The ferroelectric coil of the transformer has been removed to prevent sudden interference with the motion of the tip magnet. Only one of the coils of the transformer (the top coils) are wired to the electromagnetic load. The coils are placed in carefully machined aluminum supports. The aluminum support can be elevated and oriented using the two brass vertical screws. This allows optimal placement of the electromagnetic coils along the course of motion of the tip magnet. The tip magnet is composed of three rare earth magnets the two 12.7 X 12.7 X 12.7 mm cubic magnets are stabilized on the sides of the ferroelectric spring steel 466
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