Closure to “Discussion of â€کOn the Role of Nonlinearities in Energy Harvesting: A Critical Review and Discussion’†(Daqaq, M., Masana, R., Erturk, A., and Quinn, D. D., 2014, ASME Appl. Mech. Rev., 66(4), p. 040801)
Abstract
To begin, we would like to point out that the complexity of the response behavior of nonlinear harvesters as compared to their linear counterparts remains the biggest challenge preventing us from optimizing their performance and fully reaping their potential benefits. Nonlinear harvesters exhibit different behaviors that are not seen in linear systems including subharmonic, superharmonic, quasiperiodic, aperiodic and chaotic responses. The long time response of the system depends on its initial conditions, and they can undergo different bifurcations in the parameter space as compared to those observed in linear systems, yielding sudden jumps in the response amplitude and/or switching in its period (doubling/halving). While we are currently able to show that, for some design parameters a nonlinear harvester can outperform a linear one, we are still unable to provide distinctive guidelines on how to properly design a nonlinear energy harvester for a given excitation source. Furthermore, we are still many steps away from designing electronic circuits specifically optimized to maximize the advantages of the nonlinearity and to properly condition the complex responses typical of their behavior.