Research On The Wide Bandwidth Energy Harvesting Of Piecewise-linear Piezoelectric Energy Harvester

The past decade has witnessed the rapid development of integrated circuits and micro electro mechanical systems that enhance the application of the wireless sensor network nodes in civilian industry and national defense military field and promote the research on using piezoelectric materials harvesting the environment vibration to power the wireless sensor network node.In the current research of the piezoelectric energy harvester,most of the energy harvesters have been designed for single-degree-of-freedom linear structure that have only one natural frequency.When the frequency of the environment vibration drift out of the natural frequency,the harvesting efficiency of the single-degree-of-freedom linear energy harvester will decrease sharply and cannot availably collect the environment vibrations that usually vary in wide frequency bandwidth.herefore,looking for the structure be able to harvest the vibration in wide frequency bandwidth is of significance for enhancing the environmental adaptability and promoting the practical application process of energy harvester.In order to solve the problem,this dissertation has taken the piecewise-linear piezoelectric energy harvester with nonlinear vibration characteristics as the research object and systematically studied the mechanical-electromagnetic coupling model,the output voltage characteristic,the output voltage stability and wide frequency bandwidth harvesting characteristic with theoretical and experimental approach.The piecewise-linear energy harvester is a kind of typical nonlinear structure energy harvester.Firstly,in order to work out the inaccurate motion description problem caused by current research on single-degree-of-freedom piecewise-linear piezoelectric energy harvester using the pure mechanical model,the mechanical-electromagnetic coupling model of the single-degree-of-freedom piecewise-linear piezoelectric energy harvester have been built in this dissertation.By solving the corresponding nonlinear dynamic equations,the solution and amplitude-frequency characteristic expressions of the system output voltage have been obtained and the system power performance calculated by the pure mechanical model and the mechanical-electromagnetic coupling model have been comparatively analyzed.Based on the calculated amplitude-frequency characteristic expression of the system output voltage,theinfluences of the excitation acceleration,the cantilever beam proof mass,the stopper beam stiffness and the impact distance on the system output power performance have been studied.Then the novel two-degree-of-freedom piecewise-linear piezoelectric energy harvester has been proposed by combining the multimodal wide bandwidth harvesting technique and piecewise-linear wide bandwidth energy harvesting method,the corresponding mechanical-electromagnetic coupling model and nonlinear dynamic equations have been built.According to the averaging method,the solution and amplitude-frequency characteristic of the system output voltage expressions in the first and the second resonance region have been obtained and the system power performance in different resonance region have been analyzed.Based on the calculated amplitude-frequency characteristic expression of the system output voltage in different resonance region,the influences of the excitation acceleration,the cantilever beam proof mass,the stopper beam stiffness and the impact distance on the system output power performance in different resonance region have been studied.Based on the solution expressions of the systems output voltage calculated above,the stability of the output voltage has been analyzed and the solution conditions for the system to output stable voltage has been obtained.According to high efficiency output requirement of the piecewise-linear piezoelectric energy harvester,the excitation parametric condition has been confirmed for the piecewise-linear piezoelectric system to output stable High voltage amplitude in wide frequency bandwidth.According to the characteristic that he system output power will change with the load resistance and excitation frequency,the power output characteristic of the piecewise-linear piezoelectric system and the corresponding linear piezoelectric system have been analyzed and the wide frequency bandwidth harvesting characteristic of the piecewise-linear piezoelectric energy harvester have been studied.Finally,the experiment devices of piecewise-linear piezoelectric energy harvester have been fabricated.According to test requirements of output power performance for the piezoelectric vibration energy harvester,the experimental test platform have been set up.he output power performance and the influences of system parameters on the output power performance have been experimental studied.Meanwhile,the wide frequency bandwidth harvesting characteristic of the piecewise-linear piezoelectric energy harvester have been experimental studied by changing the excitation frequency and the load resistance.hecontrastive study between the theoretical and experimental results indicate that the electromechanical coupling model built in this dissertation can provide theoretical reference for the design and parameter optimization of piecewise-linear piezoelectric energy harvester and the piecewise-linear piezoelectric system has wider operating frequency bandwidth and higher energy harvesting efficiency when compare to the linear piezoelectric system.