260 K. Vijayan et al. 0 4 8 121620242832 10−15 10−10 10−5 100 Frequency (Hz) Power(mW) Kcont = 5000 N/m Kcont = 100 N/m 0 4 8 121620242832 10−15 10−10 10−5 100 105 Frequency (Hz) Power(mW) ζ=0.001 ζ=0.005 ζ=0.01 0 4 8 121620242832 10−15 10−10 10−5 100 Frequency (Hz) Power (mV) δ=1 mm δ=4 mm δ=7 mm a c b Fig. 28.6 Parametric study on the variation of power generated with system parameters. (a) Variation in the power produced by the system with excitation frequency for two different contact stiffnesses for a fixed damping factor of 0:01% and clearance of 4 mm. (b) Variation in the power produced by the system with excitation frequency for three different damping ratios for a fixed contact stiffness of 500 N/m and clearance of 4 mm. (c) Variation in the power produced by the system with excitation frequency for three different clearances for a fixed contact stiffness of 500 N/m and a damping factor of 0:01% was estimated. Figure 28.6a shows the variation in the average power generated across the frequencies for different contact stiffnesses. It can be observed that the power generated shows a sensitivity to the contact stiffness since it influences the number of modes excited. The power generated is significantly higher at the resonance frequencies of the individual beams. Figure 28.6b shows the variation in the average power generated across the frequencies corresponding to different damping ratios, and shows that with an increase in mechanical damping the effectiveness of the harvester reduces. The influence of clearance on the power generated is shown in Fig. 28.6c. With the reduced clearance the possibility of impact between the beams increases even in the frequency regions slightly away from the resonant peaks, where response amplitudes are generally lower. This has a positive influence on the power generated. 28.3 Conclusion The results from the study indicated that energy harvesting using impact is a viable option to improve the operational bandwidth of the harvester. Contrary to the linear system where only one mode is excited, with non-linear impact a larger number of modes are excited for the same excitation frequency. The key mechanical parameters of the system which can be
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