Optimal Design Of Piezoelectric Cantilever Beam For Specific Frequency Vibration Energy Harvesting

In some places where it is inconvenient to install or frequently replace batteries,piezoelectric energy harvesters(PEH)can be used to power electronic devices.Due to the shortcomings of narrow frequency band and low output power,PEHs have not been widely used.In this paper,facing the vibration environment of 50 Hz power frequency,the structure,electrode coverage and energy management circuit design and optimization of the trapezoidal cantilevered PEH are carried out,and through finite element simulation and experiment respectively,the optimized trapezoidal cantilevered PEH and the traditional rectangular PEH were compared in terms of energy storage,load power and intermittent power supply.According to the first-order natural frequency expression of the rectangular cantilevered PEH,the influence of the structural size of the trapezoidal cantilevered PEH on the natural frequency is studied;combined with the vibration displacement equation of the cantilever beam and the piezoelectric equation,it is revealed that reducing the electrode coverage can increase the open circuit voltage and stored energy of the PEH,and the essence is to reduce the electromagnetic energy loss caused by the uneven stress distribution of the piezoelectric cantilever beam.Through COMSOL "characteristic frequency " and "Frequency " research,the stress distribution,vibration mode,open circuit voltage,stored energy and energy density of piezoelectric cantilevers are compared,and the full piezoelectric structure,tip ratio and electrode coverage are determined.Therefore,the optimal size parameters of the trapezoidal cantilevered PEH with the first-order natural frequency of 50 Hz are designed,and the rectangular PEH with the same volume and length is used for comparison.Two kinds of PEHs were made,using optimized synchronous electric charge extraction(SECE)circuit and intermittent power supply energy management circuit with LTC3129-1 as the core.Under the same vibration conditions,the energy harvesting effect of different electrode coverage was studied,and the charging and discharging cycle and power of intermittent power supply for the temperature sensor node APC300 were compared.Both simulations and experiments show that the optimal electrode coverage of the trapezoidal and rectangular PEHs are 0.7 and 0.6,respectively.In the simulation,the energy stored in the trapezoidal PEH with 0.7 electrode coverage is 1.15 times that of the rectangular PEH with 0.6 electrode coverage.Under the same vibration conditions,using a synchronous charge extraction circuit,the recovery power of a trapezoidal PEH with 0.7 electrode coverage is 1.11 times that of a rectangular PEH with 0.6 electrode coverage;after adding the intermittent power supply energy management circuit,power the wireless temperature sensor transmitter APC300,trapezoidal PEH with 0.7 electrode coverage can charge a 0.22 F energy storage capacitor with 1.3 m W,which is 1.77 times that of a rectangular PEH with 0.6electrode coverage.In summary,the power supply capacity of the optimized trapezoidal cantilever beam piezoelectric energy harvester is twice that of the traditional rectangular piezoelectric energy harvester.