Qualitative changes in bifurcation structure for soft vs hard impact models of a vibro-impact energy harvester

Dimitri Costa* (Corresponding Author), Rachel Kuske, Daniil Yurchenko

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)
3 Downloads (Pure)


Vibro-impact phenomena in engineering systems, considered an adverse effect in some settings, are an intrinsic part of the mechanism in others. In energy harvesting, a vibro-impact component is often intentionally introduced to increase the power output or the system's bandwidth. The impacts can be treated as "hard"for instantaneous impacts or "soft"for compliant materials. Since both types of models exhibit complex dynamics, a comparison is non-trivial. We develop a soft impact model for a vibro-impact energy harvester, calibrating it with the relevant hard impact model for large stiffness, and systematically compare the different phenomena and dynamics in various compliant regimes. Numerical results are used in two different parametric analyses, considering the bifurcation diagrams in terms of device size and external forcing parameters. Varying the natural frequency of the membranes that form the impact boundaries, we observe shifts in the bifurcation structure that promote period-1 orbits for increased softness parameters, often generating higher power output, but also introducing parameter sensitivities for increased softness. Complementary analytical results reveal unstable periodic orbits and co-existing behaviors, potentially missed by computational methods, that can influence the bifurcation structure and in turn the energy output. A non-dimensional formulation highlights the significance of ratios of external and natural frequencies in delineating soft and hard impact scenarios parametrically. The soft impact model exhibits new symmetry breaking bifurcations related to key quantities that characterize the soft impact dynamics, such as the effective restitution coefficients, the impact phase, and the contact time interval, not captured by hard impact models.

Original languageEnglish
Article number103120
Number of pages24
Early online date27 Oct 2022
Publication statusPublished - 27 Oct 2022

Bibliographical note

Funding Information:
The authors gratefully acknowledge partial funding for this work from NSF-CMMI (No. 2009270) and EPSRC (No. EP/V034391/1).

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.


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