The Need

Energy harvesting from system vibrations is considered a promising green energy source with the capacity to both self-power small-scale devices and fulfill the need of large-scale electricity generation. A recent report by BCC research found that the markets for Vibration, Displacement, and Mechanical energy harvesters reached a total, global size of $500 million USD in 2018 with a projected compound annual growth rate (CAGR) of 18.5% through 2023. Vibration energy harvesting can be realized using piezoelectric, electromagnetic, or electrostatic approaches. Early designs of these power generators were based on linear models that provide the maximum power generation efficiency at resonance with their efficiency decreasing dramatically even when the excitation frequency shifts slightly. Thus, traditional linear energy harvesters are usually limited to very narrow frequency ranges.

To address this shortcoming, a variety of nonlinear energy harvesters have been proposed to broaden the frequency range; none of them, however, are as effective as linear energy harvesters operating at resonance. A class of nonlinear energy harvesters with piecewise-linear (PWL) nonlinearities have been proposed, but proper analysis and control of these systems has been a challenge. These PWL energy harvesters usually incorporate a mechanical stopper into system designs such that the effective frequency range can be broadened by the contact nonlinearity between the main oscillator and the stopper. However, these systems do not generally provide the optimized power generation efficiency at an arbitrary excitation frequency. An adjustable PWL system that adjusts based on the excitation frequency would enable optimal energy extraction over a large frequency range.

The Technology:

Researcher’s at The Ohio State University’s Nonlinear Dynamics and Vibration Lab addressed this need by devising a new technique that includes a mechanical system and a control method to optimize the vibration performance of energy harvesters. The new designs incorporate mechanical stoppers or additional sets of springs and dampers into traditional linear systems. The resonant frequencies and amplitude of these systems can then be manipulated by adjusting the gap size or prestress between mechanical elements. The benefit of utilizing PWL nonlinearity in these systems is that a wide frequency range can be covered by shifting the resonant frequency by actively controlling the gap size or prestress in these systems while maintaining the high performance of a linear system at resonance. The advantages of this technique and associated data were published in Proceedings A of The Royal Society Publishing journal on January 1 2020 (Volume 476, Issue 2233).

Commercial Applications:

• Powering of remote sensors by harvesting the system’s vibrations
• Energy harvesting devices to feed the power grid

Benefits/Advantages:

• Improved energy extraction capability and efficiency
• Applicable to a wide range of excitation frequency and amplitude
• Computational efficiency suitable for complex mechanical designs
• Compatible with systems which contain gaps or prestress

Research Interests:

The Nonlinear Dynamics and Vibration Laboratory that developed this technology has expertise in the analysis and study of systems exhibiting nonlinear dynamics covering a wide variety of fields and applications, including: studying piecewise linear nonlinear systems; design of vibration absorbers; structural health monitoring for nonlinear systems; sensing using vibration based methods; forecasting bifurcations in nonlinear systems; creating tools for modeling and analyzing high dimensional cyclic structures such as those found in gas turbine engines, and; full scale rotating experiments of bladed disks.