Study On A Prebending-cantilever Piezo-Harvester Excited By Rotary Magnet

To meet the demands of monitoring system for self-power,a prebending-cantilever piezo-harvester excited by rotary magnet was presented,and its output performance was studied from both theory and experiment.The main contents are as follows:The COMSOL simulation model of the piezoelectric harvester is established,and its prebending radius,length ratio(The ratio of the piezo-cantilever's length and the length of the substrate),thickness ratio(The ratio of substrate thickness to total thickness of piezoelectric harvester)and material(Young's modulus ratio)were analyzed.The effects of these elements on the rigidity,deformation,stress distribution and etc output performanc of the harvester were gained.The results show that ?in the direction of the length of the piezoelectric harvester,there exists a sudden change of stress and a node with zero stress,and all parameters have great influence on the deformation and stress characteristics of piezoelectric harvester.? The young's modulus has a great influence on the deformation and stress characteristics of piezoelectric harvester.When the length/thickness ratio is constant,the longitudinal displacement decreases and the stress increases with the increase of Young's modulus ratio.?The fundamental frequency and vibration mode of piezoelectric vibrator are related to the deformation and the stress distribution,and the vibration mode depends on the external excitation frequency and the fundamental frequency.The change of piezoelectric vibrator length ratio and thickness ratio can properly adjust the first-order natural frequency;When the external excitation frequency is less than the first natural frequency of the piezoelectric vibrator,the deformation and stress distribution are favorable.The effects of the incentive form of magnets as well as other related factors on the output performance of the harvester ware analyzed by COMSOL.The structure and working principle of the piezoelectric energy harvester were presented,and the dynamic response model of the system was established with the vibration theory and the incentive form of magnets we gained.The relationship between the magnet ratio(ratio of the number of moving magnets to the maximum number of magnets arranged on the turntable),the radius of gyration,system stiffness,and output performance of the harvester was obtain by MAPLE either.The results show that the amplitude amplification ratio decreases with the increase of the added mass and increases with the increase of the stiffness.The output voltage increases with the increase of the number of magnets and the radius of rotation,and the optimal speed decreases with the increase of the mass ratio of the magnet and the added mass.For the correctness of the theory and simulation,a prototype was made to have a test,the effects of distance and number of magnets,additional mass,spring stiffness and prebending radius on output performance ware gained.Power test was done in different speed,external resistance and number of magnets.Results show that the output voltage decreases with the increase of the magnet distance,the number of moving magnets,the added mass and the spring stiffness.The voltage increases and then decreases with the increase of the number of magnets and increases with the increase of the bending radius.The output voltage is the maximum when the external resistance is equal to the internal resistance.