Towards self-powered tunable mechanical oscillators: A conceptual study

Abstract

Mechanical oscillator resonance frequencies are of paramount importance and determine their performance from different perspectives such as bandwidth, vibration mitigation, and energy harvesting. As active tuning is hindered by energy consumption, this research investigates comprehensively for the first time if the inherent energy of a vibrating oscillator can supply the required energy to alter its natural frequency. To investigate the viability of this concept, a nonlinear partially covered piezoelectric beam-based oscillator with a full bridge rectifier and magnetic tuning mechanism under base excitation is considered, and its geometrically nonlinear model is derived. First, an approximate solution is proposed to study the capacitor charging process in steady-state excitation. Then, numerical integration and the multi- harmonic balance method (HBM) with pseudo-arclength continuation are exploited to investigate the nonlinear dynamics, mechanical response, and external capacitor voltage of the self-powered tunable oscillator (SPTOS). To investigate the sufficiency of the SPTOS energy for tuning, the required energy for different levels of change in the SPTOS natural frequency are obtained. It is found that the SPTOS can supply the energy to significantly change its natural frequency. The capacitor charging time and generated energy depend on the ratio of external capacitance to internal capacitance. The SPTOS efficiency under chirp excitation is then investigated, and the results show that both the chirp rate and the capacitance ratio affect the capacitor energy. Finally, by comparing the maxima of energy for the steady-state and chirp excitations, it is shown that the SPTOS energy in the former case is considerably higher than the latter case. Thus, the SPTOS can make larger changes in its frequency when excited in a steady-state scenario.