Nonlinear Piezoelectric Energy Harvesting Circuit And Its Application On Road Condition Monitoring

The presence of abundant mechanical vibration energy in road environment draws engineer’s attention. This kind of energy can be transferred into electric energy by using the piezoelectric energy harvest technology, which could be an efficient way to solve the huge energy requirements of the wireless sensors system in the road condition monitoring system. Combining the new technologies in the mechanics and electric areas, the theoretical, numerical and experimental studies will be conducted in this thesis to study the nonlinear piezoelectric energy harvesting circuit and its application on road condition monitoring. The main research contents and results of this work are as follows:1. Combining the piezoelectric equations and cantilever beam theory, the dynamic properties of the piezoelectric cantilever beam are analyzed, from which the mechanical and electrical energy conversion model of piezoelectric cantilever beam is given; Based on the equivalent model of piezoelectric cantilever beam, a comprehensive comparison study is conducted to investigate the energy output properties of five kinds of interface circuit(Series SSHI Interface Circuit, Parallels SSHI Interface Circuit, Standard Interface Circuit, VD Interface Circuit and SECE Interface Circuit);2. With proper design, the piezoelectric cantilever beam model is used to design the energy harvest structure. By using the Multiphysics Finite Element Software (Comsol), numerical simulations are conducted to study the efficiency of the proposed structure, from which the electromechanical equivalent model is established; furthermore, by using the cantilever beam of electromechanical model, numerical analysis of the several kinds of interface circuit is conducted by PSPICE software;3. Two kinds of energy harvesting circuits, the standard energy harvesting circuit and the VD energy harvesting circuit, are designed. By using numerical simulations, energy harvesting characteristics of these two circuits are studied comparatively. The results show that the efficiency of the VD energy harvesting circuit is much better than the standard energy harvesting circuit;4. An experimental study of the proposed piezoelectric cantilever beam harvesting structure is designed and conducted to study the efficiency of different kinds of interface circuits and the harvesting circuits. It is proved that the power loss of the VD interface circuit is much lower than that of the standard interface circuit; the output power of the VD energy harvesting circuit is 1.18 times of the standard energy harvesting circuit. Therefore, the efficiency of the VD circuit is verified.This thesis studied the piezoelectric cantilever beam energy harvesting circuits and its energy harvesting properties, which is a fundamental work for the application of the piezoelectric structure for harvesting road mechanical vibration energy. Also, the research achievements of this work could be a new way to solve the huge energy demand for the road wireless condition monitoring systems.