Shunong Jiang

Performance of a piezoelectric bimorph for scavenging vibration energy

We analyze the performance of a piezoelectric bimorph in the flexural mode for scavenging ambient vibration energy and evaluate the dependence of the performance upon the physical and geometrical parameters of the model bimorph. The analytical solution for the flexural motion of the piezoelectric bimorph shows that the output power density increases initially, reaches a maximum, and then decreases monotonically with increasing load impedance, which is normalized by a parameter that is a simple combination of the physical and geometrical parameters of the scavenging structure, the bimorph, and the frequency of the ambient vibration, underscoring the importance for the load circuit to have the impedance desirable by the scavenging structure. The numerical results illustrate the considerably enhanced performances achieved by adjusting the physical and geometrical parameters of the scavenging structure.

Weakly nonlinear behavior of a plate thickness-mode piezoelectric transformer

We analyzed the weakly nonlinear behavior of a plate thickness-shear mode piezoelectric transformer near resonance. An approximate analytical solution was obtained. Numerical results based on the analytical solution are presented. It is shown that on one side of the resonant frequency the input-output relation becomes nonlinear, and on the other side the output voltage experiences jumps

Experimental research on nonlinear coupling between two sides of rectification in piezoelectric energy harvester

This paper proposes a piezoelectric energy harvester experiment model, which composed of piezoelectric harvesting element, energy storage element, and a full bridge to connect them as an integrated system. A synchronized switch harvesting inductor (SSHI) is introduced in parallel with the harvesting structure to reverse voltage through the charge transfer between the output electrodes at the transition moments from closed- to open- circuit, i.e. the time when the harvesting structure deforms to the extreme position. The harvesting structure is driven to vibrate by vibration exciter which is acted by a voltage signal with a certain frequency. The method of capturing zero velocity is used to catch the moment when the harvesting structure deforms to the extreme position. SSHI closes synchronously, and delay a half period of the oscillator, composed by the inductor and effective capacitor of piezoelectric harvesting structure, then opens. This process is controlled by the technique of single chip microcomputer. Experimental results show SSHI processes have been achieved. An optimal rectified voltage can maximize the output power density of the piezoelectric energy harvester.

Effect of polymer layer on the performance of piezoelectric harvester in thickness-shear vibration

Because of its relatively high resonant frequency, a thickness-shear mode piezoelectric harvester composed of a cylindrical piezoelectric ceramic shell is not suitable for converting mechanical energy to electrical energy from ambient vibration sources, most of which are of low frequencies. Therefore, its important for us to reduce the resonant frequency so as to enlarge the application domain of the harvester, and the traditional method is to increasing the attached mass or the thickness of the piezoelectric shell. But if we want to decrease the system resonant frequency much more, some new ideals must be proposed. This article presents an efficient approach to decrease the resonant frequency by fixing a polymer layer at the inner surface of the piezoelectric shell. Based on the linear piezoelectricity theory, the effects of the geometrical parameters of the polymer layer on the performance of the piezoelectric harvester are analyzed. Numerical results indicate that the use of polymer layer can considerably reduce the system resonant frequency.