Optimum Design Of Electrode For Piezoelectric Cantilever Beam Vibration Energy Harvester

There are various forms of mechanical vibration energy in the environment,using the piezoelectric energy harvesting system to convert the vibration energy into electric energy,thus providing power for low-power electronic devices,which has a relatively large research value.Piezoelectric cantilever beam was the most commonly used energy transducing component,its structure,dimensions,electrode distribution,etc.,which affect the electrical properties of piezoelectric harvester.In this paper,the effect of electrode distribution on the energy harvester characteristics of piezoelectric cantilever beam was studied from the perspective of the electrode ratio.Firstly,the rectangle and triangle beam have been modeled by ANSYS,and the static,modal,harmonic response analysis and transient simulation analysis have been carried out.And simulated the output characteristics of two cantilever beams at different electrode ratios.The result showed that,the rectangular and the triangular beam have the maximum output power when the electrode ratio was 50% and 60%,respectively.And the output open-circuit voltage and matched load decreased with the increase of the electrode ratio.Secondly,the relationship between the electric field energy and the electrode ratio stored in the process of energy harvesting for rectangular and triangular beams was deduced by mode shape function of the piezoelectric cantilever beam.When there is no mass at the end,the optimal electrode ratio is 52% and 57% respectively.When there was a mass at the end of a rectangular beam,in the process of increasing the relative mass ratio of mass and cantilever beam from 0 to 0.85,the optimal electrode ratio increased from 52% to 67%,when the relative mass ratio is greater than 0.85,the optimal electrode ratio is 67%.Besides,the essence of the effect of electrode ratio on the output characteristics of cantilever beam has been explored,it was clear that the characteristic of the inhomogeneous distribution of the strain of the cantilever beam in its first-order mode,which determined charge redistribution process existed.Loss of energy existed during this process,and the lost energy was dissipated in the form of electromagnetic radiation.Thirdly,the verification experiments of rectangular and triangular beams have been done.The results proved the existence of the optimal electrode ratio of rectangular and triangular beams,the maximum output power of rectangle and triangle beam was acquired when the electrode ratio was 60% and 50% respectively,which is 1.45 times and 1.17 times the maximum output power when the electrode ratio was 100%.At last,the electrode optimization method proposed in this paper was applied to the PZT cantilever beam,using the LED lamp as the load.The comparison of the brightness and the number of lights further verified the presence of its optimal electrode ratio.The results showed that when lighting three LEDs,the maximum output power of 50% was 3.8 times higher than 100%,which proved the significance of the optimum design of electrode for piezoelectric cantilever beam vibration energy harvester.In summary,both theoretical analysis and experimental results showed that the rectangular and triangular piezoelectric cantilever beams have the optimal electrode ratio,and the optimal ratio is between 50% and 60%.In practical applications,output power and energy conversion efficiency can be improved by optimizing the electrode ratio.The work of this paper provided guidance for the optimal design of electrodes in piezoelectric energy harvesting systems.