(a) (b) (c) Fig. 6: Relation between the magnet distance and a) tip velocity transfer function, b) piezoelectric power transfer function, c) electromagnetic power transfer function. Base acceleration As illustrated in Fig. 7 the nonlinear behavior intensifies with the base acceleration. Since the type of nonlinearity is hardening this results in some decrease in the amplitude of motion and correspondingly the harvested power. The power drop in electromagnetic harvesting is more visible for the reasons discussed in previous sections. (a) (b) 4 6 8 10 12 14 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 R 1 =100k, R 2 =5, a b =1.47, legend: (mm) Frequency (Hz) Tip vel/ Base accel (1/S) 37 45 58 4 6 8 10 12 14 0 0.2 0.4 0.6 0.8 1 1.2 1.4 x 10 -3 R 1 =100k, R 2 =5, a b =1.47, legend: (mm) Frequency (Hz) PZT power/ Base accel 2 (Kg.S) 37 45 58 4 6 8 10 12 14 0 1 2 3 4 5 6 7 8 x 10 -5 R 1 =100k, R 2 =5, a b =1.47, legend: (mm) Frequency (Hz) E.M. power/ Base accel 2 (Kg.S) 37 45 58 4 5 6 7 8 9 0 0.05 0.1 0.15 0.2 0.25 R 1 =100k, R 2 =5, =37(mm), legend: a b Frequency (Hz) Tip vel/ Base accel (1/S) 0.15 0.29 0.74 1.47 2.94 4 5 6 7 8 9 0 0.2 0.4 0.6 0.8 1 1.2 1.4 x 10 -3R 1 =100k, R 2 =5, =37(mm), legend: a b Frequency (Hz) PZT power/ Base accel 2 (Kg.S) 0.15 0.29 0.74 1.47 2.94 470
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