Extending the dynamic range of an energy harvester with a variable load resistance

Abstract

Abstract. In some energy harvesters, the maximum throw of the seismic mass is limited due to the physical constraints of the device. The shunt load resistance of such a harvester is generally selected based on the allowable throw of the mass when the device is subjected to the maximum level of excitation. However, the energy harvester with this value of shunt resistance does not perform well at lower levels of excitation. In this paper, a variable load resistance, scheduled on the excitation level, is introduced to extend the dynamic range of an energy harvester in applications where excitation level varies. This method is applied to the design of an energy harvester, which comprises of a sprung-mass coupled to an electric motor through a lead screw. The dynamic equation and parameters of the system are introduced and the device is experimentally characterized, by conduction the random vibration test. The harvested power and the relative displacement are then obtained for different sinusoidal base excitation amplitudes when the system is excited at the frequency close to its natural frequency. It is demonstrated that the use of a variable load resistance mechanism can significantly improve the dynamic range and output power of the energy harvester.

Low power energy harvesting systems: State of the art and future challenges

“…It also mentioned that the internal resistance of this energy harvester depends on the number of cycles of input sinusoidal wave. While for the electromagnetic harvester, Hendijanizadeh et al [61] installed an intelligent control device to switch between cubic and linear load resistance to optimise the power output of the electromagnetic energy harvester in different frequencies and amplitude excitations condition in the actual environmental state. The result of the study showed that the internal resistance of the electromagnetic plays a significant role in choosing the maximum load resistance for the energy harvesting system and it must be recognized in the control technique design.…”

Investigative Study of the Effect of Damping and Stiffness Nonlinearities on an Electromagnetic Energy Harvester at Low-Frequency Excitations

“…It was demonstrated that the piecewise nonlinear stiffness behaviour, developed due to the interactions of the moving magnet's flux on the coil, facilitated the response of the system in a wider frequency range, enabling it to generate more electrical energy. Similarly, system damping characteristics have been employed in optimising the energy harvested by vibration energy harvesters [16][17][18][19][20][21][22][23][24]. In [16], the authors presented an unconventional way of achieving a tuneable resonant frequency (from high frequency to ultralow frequency) and extending both the bandwidth and peak of the energy harvested, simultaneously, by utilising a distinct structurally supported displacement-dependent nonlinear damping property.…”

“…In [16], the authors presented an unconventional way of achieving a tuneable resonant frequency (from high frequency to ultralow frequency) and extending both the bandwidth and peak of the energy harvested, simultaneously, by utilising a distinct structurally supported displacement-dependent nonlinear damping property. This work was further extended by the authors in [17], Similarly, system damping characteristics have been employed in optimising the energy harvested by vibration energy harvesters [16][17][18][19][20][21][22][23][24]. In [16], the authors presented an unconventional way of achieving a tuneable resonant frequency (from high frequency to ultralow frequency) and extending both the bandwidth and peak of the energy harvested, simultaneously, by utilising a distinct structurally supported displacement-dependent nonlinear damping property.…”

“…The authors in [21,22] also employed nonlinear damping in extending the energy harvested by a vibration energy harvester. Based on the findings in [21,22], an analysis, design, and optimisation of a nonlinear VEH system was conducted in [23,24]. While no mass-displacement constraint was considered in [23], this was considered in [24].…”

A self-tuning vibration energy harvester with variable loads and maximum allowable displacement

“…However, a look-up table is used for tuning based on a priori knowledge of the harvester. More recently, a similar approach was presented in [17] for extending the dynamic range of a harvester when the input displacement and frequency are variable. However, this approach utilizes an experimental model of the system.…”