Enhanced Vibration Energy-Harvesting Using Inerter-Based Two-Degree-of-Freedom System

2018 ◽  
Author(s):  
Mingyi Liu ◽  
Wei-Che Tai ◽  
Lei Zuo
Keyword(s):  
Energy Harvesting ◽  
Degree Of Freedom ◽  
Power Stroke ◽  
Specific Power ◽  
Vibration Energy ◽  
Frequency Bandwidth ◽  
Vibration Energy Harvesting ◽  
Sdof System ◽  
Harvesting Systems ◽  
Two Degree Of Freedom

In rotational electromagnetic generator based vibration energy-harvesting systems, the generator rotor is an inerter. From analysis, it is found that the inerter decreases system frequency bandwidth in single-degree-of-freedom (SDOF) energy-harvesting systems. The maximum electric power output of a SDOF system is limited by mechanical damping and maximum stroke that allowed. Two-degree-of-freedom (2DOF) energy-harvesting systems was proposed in recent years and has been shown to have the potential to have better power, power/stroke ratio, and frequency bandwidth performance compared with SDOF systems. However, extra mass has to be added in most of the case. In this paper, a new design of inerter-based-2DOF energy-harvesting system was proposed by adding a spring in series with the inerter in SDOF system. No extra mass is added compared with its counterpart SDOF system. Optimal specific power at limited stroke were obtained by tuning system parameters, which includes resonance frequency ratio, spring ratio, mass ratio, and damping ratio. The contribution of each parameter to system performance was analyzed. The results show that the proposed inerter-based-2DOF system has better performance compared with the SDOF system. The inerter-based-2DOF can have larger specific power and larger power/stroke ratio over a wider frequency bandwidth. Simulation also show that improved performance not only obtained with sinusoidal excitation with constant displacement amplitude, but also with sinusoidal excitation with constant force amplitude.

scholarly journals A Theory for Energy-Optimized Operation of Self-Adaptive Vibration Energy Harvesting Systems with Passive Frequency Adjustment

Micromachines ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 44 ◽  
Author(s):  
Mario Mösch ◽  
Gerhard Fischerauer
Keyword(s):  
Energy Harvesting ◽  
Resonance Frequency ◽  
Optimal Operation ◽  
Energy Output ◽  
Vibration Energy ◽  
Vibration Energy Harvesting ◽  
Vibration Energy Harvester ◽  
Frequency Adjustment ◽  
Harvesting Systems ◽  
Self Adaptive

Self-adaptive vibration energy harvesting systems vary their resonance frequency automatically to better exploit changing environmental conditions. The energy required for the adjustment is taken from the energy storage of the harvester module. The energy gained by an adjustment step has to exceed the energy expended on it to justify the adjustment. A smart self-adaptive system takes this into account and operates in a manner that maximizes the energy output. This paper presents a theory for the optimal operation of a vibration energy harvester with a passive resonance-frequency adjustment mechanism (one that only requires energy for the adjustment steps proper, but not during the hold phases between the steps). Several vibration scenarios are considered to derive a general guideline. It is shown that there exist conditions under which a narrowing of the adjustment bandwidth improves the system characteristics. The theory is applied to a self-adaptive energy harvesting system based on electromagnetic transduction with narrowband resonators. It is demonstrated that the novel optimum mode of operation increases the energy output by a factor of 3.6.

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