| At present,it is deepening of the intelligent and wireless development in pneumatic system.In order to powered for wireless sensors in pneumatic system,this paper proposes the development method of piezoelectric energy harvester to meet the wireless power supply requirements in pneumatic system.Piezoelectric energy harvester uses air pressure energy as the power source and piezoelectric materials as the force-electric conversion medium to realize the conversion of pressure energy to electric energy in a limited space.The paper content is to provide a new solution for the wireless power supply of pneumatic sensors.In this paper,the basic structure of the multi-cavity piezoelectric energy harvester is proposed which can directly convert the air pressure energy into electrical energy.Taking the piezoelectric patch bonded by two or more materials as the research object,the three-dimensional finite element mechanical-electrical coupling model of the multi-zone piezoelectric patch is established,and the effects of the shape size,fixed boundary constraints,load conditions,and adhesive thickness on the amount of charge generated are studied of the piezoelectric patch.Combined with the characteristics of charge distribution,the piezoelectric patch is preloaded,and the degree of charge enhancement is studied by changing the energy distribution of the piezoelectric patch.A method of removing some materials to increase the proportion of electric energy of piezoelectric patch is proposed.By judging and sequencing the volume strain of piezoelectric patch,the area with high proportion of strain energy is removed,so that the electric energy and strain energy are redistributed,and finally the purpose of increasing the amount of available charge is realized.Aiming at the problem that the change rate of air pressure is too slow to affect the output performance,a transient power generation model is established of piezoelectric energy harvester.The model is used to study the influence of the parameters such as the diameter of the inlet hole,the height of the cavity and the diameter of the cavity on the output voltage,capacitance,internal resistance and other parameters of the piezoelectric patch,so as to obtain the pressure change conditions.The air-solid coupling characteristics of the piezoelectric energy harvester are analyzed,and the driven law between the piezoelectric patch and the compressible air is analyzed under the same scale conditions of the harvester height and the deflection of the piezoelectric patch.The time characteristics of the pressure change with the air inflow and outflow are analyzed by changing the diameter of the inlet hole,and the transient power output by the piezoelectric patch is analyzed.The piezoelectric energy harvester with high power output provides the basis for numerical calculation.Carry out the analysis of the influence of the electrical connection mode of the multiple piezoelectric patches on the power.By establishing the electromechanical conversion models of the series,parallel and hybrid connection of the multiple piezoelectric patches,analyze the relationship between the number of piezoelectric patches and the load power under different connection modes,and then carry out the experimental test of the electrical connection mode between the piezoelectric patches,and obtain a better electrical connection mode by combining the output power and impedance characteristics.In view of the problem of electric energy loss caused by the mutual interference of output charges between layers of multi-cavity piezoelectric energy harvester,a charge accumulation model of piezoelectric patch group with phase difference is established.Through theoretical analysis of the loss law of induced charges between piezoelectric patch groups,a numerical calculation platform for the influence of phase between piezoelectric patch groups on output power is built,and the degree of output power loss caused by phase difference is analyzed.Under the guidance of theoretical analysis,an experimental testing system of phase characteristics is built to test the loss of phase difference on output power,and then the allowable range of phase difference of piezoelectric patch group is obtained.Combined with the proposed phase difference allowance standard,the numerical calculation of the inter-layer phase characteristics of the multi-capacity cavity is carried out,so that the time difference of the inter-layer dynamic pressure change can meet the use requirements.Based on the theoretical analysis and simulation results,the prototype of basic power generation characteristics under pneumatic conditions.The prototype of preloaded energy storage to improve power generation and the prototype with tapered thickness piezoelectric patches are processed and systematically built,and the output voltage and power characteristics of each prototype under pneumatic conditions are analyzed.Based on the current research level at home and abroad,the energy index of the harvester with a volume of no more than 15 m L and an effective power of no less than 25 m W is proposed,and the development of the multi-cavity piezoelectric energy harvester is carried out,and the electrical energy testing experimental system is built.The average output voltage,current,effective power and other parameters of the harvester are tested.The purpose of using the multi-cavity piezoelectric energy harvester is achieved to directly supply power to low-power sensors in the pneumatic system,and it also can store energy in the capacitor battery. |
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