Stabilisation of the high-energy orbit for a non-linear energy harvester with variable damping

Abstract

The non-linearity of a hardening-type oscillator provides a wider bandwidth and a higher energy harvesting capability under harmonic excitations. Also, both low-and high-energy responses can coexist for the same parameter combinations at relatively high excitation levels. However, if the oscillator's response happens to coincide with the low-energy orbit then the improved performance achieved by the non-linear oscillator over that of its linear counterpart, could be impaired. This is therefore the main motivation for stabilisation of the high-energy orbit. In the present work, a schematic harvester design is considered consisting of a mass supported by two linear springs connected in series, each with a parallel damper, and a third-order non-linear spring. The equivalent linear stiffness and damping coefficients of the oscillator are derived through variation of the damper element. From this adjustment the variation of the equivalent stiffness generates a corresponding shift in the frequency-amplitude response curve, and this triggers a jump from the low-energy orbit to stabilise the high-energy orbit. This approach has been seen to require little additional energy supply for the adjustment and stabilisation, compared with that needed for direct stiffness tuning by mechanical means. Overall energy saving is of particular importance for energy harvesting applications. Subsequent results from simulation and experimentation confirm that the proposed method can be used to trigger a jump to the desirable state, thereby introducing a beneficial addition to the performance of the non-linear hardening-type energy harvester that improves overall efficiency and broadens the bandwidth.

Power enhancement of a monostable energy harvester by orbit jumps

“…Besides, mechanically or electrically tuning the system stiffness could also disturb the energy harvester and led to orbit jumps (Huguet et al, 2019; Yan et al, 2019). Similarly, increasing or decreasing damping in the energy harvester could also perturb the system and achieve orbit jumps (Su et al, 2016; Wang and Liao, 2019). Common issues for the parameter disturbance methods are the high power consumption for introducing perturbation and low capability over a wide frequency band.…”

A nonlinear multi-stable piezomagnetoelastic harvester array for low-intensity, low-frequency, and broadband vibrations

“…To face this dilemma, several studies proposed the use of active tuning mechanisms that may help the harvester to perform the desirable large-amplitude interwell oscillations over a wider range of frequencies, e.g. tuning the stiffness and/or damping coefficients by active control [33], or discharging a capacitor into piezoelectric layers [34],…”

Variable pitch spring for nonlinear energy sink: Application to passive vibration control

“…Particularly in the areas of aero-space and civil engineering, absorbers are required to be light and to work over a broad spectrum of frequencies, leading to increased interests in exploiting the absorber with different nonlinearities (e.g. vibro-impact, monostable duffing, non-polynomial and bistable oscillators) [2][3][4][5][6][7][8].…”

“…vibro-impact, monostable duffing, non-polynomial and bistable oscillators). 2–8 Among such devices, the nonlinear absorber with cubic stiffness, also called the nonlinear energy sink (NES), has proved to be effective for moderate-energy vibration mitigation. 1 This type of absorber is characterized by a secondary mass strongly coupled via a cubic stiffness to the primary system that needs to be protected.…”