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Design and Analysis of a Unimorph Piezoceramic Generator with Cantilever Structure in a Low-Frequency Environment

Piezoelectric materials have the electromechanical capability of converting mechanical vibration energy into electrical energy and are utilized in sensors, generators, and actuator applications. However, with regard to compact-dimension applications, piezoelectric generators have to overcome some shortcomings, such as high voltage, low current, and relatively low power output. This article presents a design method of which the loading-weight vibration on the piezoelectric material can be transferred into an external force, and, additionally, an equivalent electric circuit method is used to calculate the electrical characteristics of piezoelectric material. Compared to the measurement, in a 4 Hz vibration environment with a 30 g loading mass, which is equivalent to a 0.5 N external force, the piezoelectric plate can generate an electric voltage of 19.8 V. A 2.7 per cent error rate of the output voltage in the equivalent force conversion is achieved. Finally, in order to demonstrate the accuracy of the theoretical analysis, a prototype hand-shaking piezoelectric generator is proposed, which is used to drive a wireless-switch device (5 V driving voltage). Experimental results show that the average electrical power of the hand-shaking piezoelectric generator is approximately 50 μW, and a 7 per cent stored power error rate is achieved when comparing the measurement and theoretical estimation.