Study On Bridge Shaped Nonlinear Piezoelectric Vibration Energy Harvester

There is abundant vibration energy around the environment,such as vehicles,bridges and roads.Taking use of those vibration energy to supply ultra-low power wireless sensors has become a hotspot in recent years.The piezoelectric energy harvester is a kind of vibration energy harvester based on the positive piezoelectric effect,which has a simple structure and can provide a stable voltage output.However,most piezoelectric vibration energy harvesters only have a rather ideal output at the resonant frequency.Once the external excitation frequency deviates from the resonant frequency,the voltage output will drastically decrease,making it difficult to meet the needs of electrical appliances.Therefore,in order to solve the above problem of narrow working band,a bridge shaped piezoelectric energy harvester is proposed to broaden the frequency band for energy harvesting,and the device can adjust the natural frequency of the system adaptively to match the external excitation band.Firstly,based on the assumption of two-dimensional nonlinear Euler-Bernoulli beam,the geometric nonlinear relationship of large deformation strain-displacement is obtained;the distributed parameter dynamic model of the bridge shaped structure is obtained using Hamilton principle,and the first order response of the system is obtained by Galerkin method;after variation and nondimensionalized,the dimensionless electromechanical coupling equation is obtained;the electromechanical coupling equations were solved based on the harmonic balance method,and the approximate expressions of the voltage amplitude and average power were obtained.Then,using Matlab software,the model was analyzed and numerically solved.The effects of excitation frequency,excitation amplitude,mass position and load on the output of the bridge shaped piezoelectric energy harvester were studied,and the moving proof mass was further investigated.Based on the Multiphysics COMSOL finite element software,the mode shape and output voltage of the bridge piezoelectric energy harvester under different mass positions were obtained.Finally,the prototype and experimental base of the bridge shaped piezoelectric energy harvesting device were designed and fabricated.Through a series of experiments,the first-order voltage response curves of the bridged piezoelectric energy harvester under different excitation conditions and mass positions were obtained.The experimental results show that the bridge piezoelectric energy harvester structure can broaden the working frequency band for energy harvesting,and the output voltage is maximum when the mass block is located at the edge of the piezoelectric beam.In addition,the dynamic effect of the moving mass on the output characteristics was experimentally tested.It was found that the moving mass can increase the voltage output of the bridge energy harvester by changing the resonant frequency of the bridge shaped piezoelectric structure and impacting the piezoelectric beam.