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Vibration-based energy harvesting with a clamped piezoelectric circular diaphragm: analysis and identification of optimal structural parameters

Due to many potential promising applications, vibration-based piezoelectric energy harvesters (VPEH) with a clamped circular diaphragm are an intensively studied design in the field of piezoelectric energy harvesters. Nonetheless, their performance still leaves space for improvement, which is the primary target of this article. We define two structural parameters, namely the ratio ϖ1 between the bonding area and the piezoceramic diameter as well as the ratio ϖ2 between the clamping rim and the substrate diameter, to characterize these structures. A vibration model is developed in order to provide an analytical foundation for the identification of optimal parameters ϖ1 and ϖ2. It is verified by finite-element simulations and substantive experiments. The results allow to relate the device performance, including resonance frequency and output power, to ϖ1 and ϖ2. This shows that the output rises with increasing ϖ2, and that the maximum output for a given ϖ2 always lies in the range ϖ 1 ∈ ( 0.1, 0.2 ) . Based on this observation, an improved harvester structure with a pre-stress of 0.3 N is identified, that exhibits a matched power up to 16.3 mW at 219 Hz. This demonstrates the feasibility to achieve VPEHs with higher outputs and lower eigenfrequency through simultaneous modification of ϖ1 and ϖ2, which is highly beneficial for low-frequency energy harvesting.