Unimorph PZT Cymbal Design in Energy Harvesting

This paper presents power generation performance of unimorph PZT (lead zirconate titanate) cymbal harvesters optimally designed for the power requirements of a specific application. Proof-of-concept work has shown that the traditional cymbal design can be adapted to a new design that is capable of sustaining higher mechanical loads by replacing the piezoelectric plate with a unimorph circular piezoelectric diaphragm between the metal end caps. The unimorph circular diaphragm is constructed by bonding PZT to a steel substrate to provide increased strength. Additional work was performed to prepare the new cymbal design for large-scale implementation in a variety of applications. The parameters that affect energy harvesting performance for the cymbal structure are first optimized by parametric studies to produce optimum generated energy from a specific range of applied cyclic forces. Key parameters in the unimorph PZT cymbal design include the material properties and the dimensions of the end caps, the ratios of the diameters of the unimorph disc and the end cap cavity, and thickness ratio of the PZT layer and the substrate. Based on the optimized unimorph PZT cymbal structure, a specimen was then fabricated and tested on the load-frame to validate analytically predicted energy generating performance. The specimen was tested under a 1 Hz cyclic load of up to 2,100 N. The measured open circuit output voltages for two different load inputs were in accordance with the analytical prediction.