Characterization on Resonant Shifting of Cantilever Based Piezoelectric for Battery-Less Low Frequency Acceleration Measurement

Abstract

Piezoelectric cantilever is a structure that can translate maximum mechanical vibration energy into an electrical signal used as both sensor and generator or vice versa. At a frequency near to the resonant of the piezoelectric cantilever, larger deviation angle can be achieved which lead to potentially higher electrical power can be generated; therefore piezoelectric cantilever is mostly functioned as a micro-power generator at resonance region. While at a non-resonant frequency, the voltage output generated is rather linear and proportional to the acceleration level of the vibration; therefore in this non-resonance region, piezoelectric cantilever often functions as an accelerometer. This paper shows the potential of the ready-made piezoelectric cantilever to be altered in order to perform as a self-powered accelerometer which is independent to the influence of the frequency. The output response of the piezoelectric cantilever is characterized by modifying the length of the cantilever. The cantilever length is reduced in order to shift the resonant frequency region of the piezoelectric cantilevers to higher frequency region to make sure that the output is independent toward the vibrating frequency. The resonant frequency of cantilever at its original condition is 290H. After length reduction of 0.7cm, the resonant frequency increased to 320Hz. The resonant frequency of the cantilever continues shifted to 400Hz after length reduction of 1.0cm, 500Hz for length reduction of 1.2cm, and lastly 780Hz for length reduction of 1.5cm. After the resonant frequency of the cantilever is shifted to 780Hz, the linearity of the piezoelectric cantilever improved from 90% deviation at a frequency range of 100Hz to 250Hz, to 15% deviation at a frequency range of 100Hz to 300 Hz. These results show a major improvement in the linearity of the output of the piezoelectric cantilever when the resonant frequency is a shift away from the operating frequency.