This article presents a resonance-type vibration energy harvester with a Duffing-type nonlinear oscillator that can perform effectively in a wide frequency range. To mitigate the power-bandwidth trade-off in conventional linear harvesters, the resonance frequency band of the harvester is expanded by introducing a Duffing-type nonlinear oscillator in order to enable the harvester to generate larger electric power in a wider frequency range. Such a nonlinear oscillator, however, can have multiple stable steady-state responses in the resonance band with different levels of regeneration energy. In this study, the principle of self-excitation is utilized to destabilize the solutions, except for the highest energy solution. A load circuit with a switch between the conventional load circuit and a negative resistance circuit and the switching control law, which depends on the amplitude of the oscillator's response, are introduced to impart the self-excitation capability in order to entrain the oscillator with the excitation only in the highest energy solution. Theoretical and numerical analyses are conducted to show that the proposed harvester can respond in a large amplitude in a wide frequency range, and a significant improvement in the regenerated power is achieved as compared to the one without self-excitation control.

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This study concerns a electromagneticvibratjon energy harvester with a nonlinear oscillator ． The nonlinear oscillator can have multiple stable steady − state responses in resonance band typically the large and small amplitude solutions ClepenCling on the initial condition ． We introduce a selfLexcitation circuitWith a variable resistance which varies from negative to positive as fUnction of the induced voltage in order to enable the oscil ］ ator entrained by the excitation only in the large arnplitude solution ． This controlled resistance enables the oscillator to be entrained by the excitation in a large amplitude solution ． In this paper， the matching condition of the load resistance for the nonlinear vjbration energy harvester is mainly discussed ．【t is shown that the optimal load resistance is derived in a simplified form based on the approximated solution obtained by the averaging method ．