Research And Design On Piezoelectric Wind Speed Sensing System

When the aircraft is flying,the uncertainty of the external environment will cause its external flow field to constantly change.For example,the abrupt change of the air flow could cause the aircraft to jolt,and affect the control of aircraft.Therefore,some sensors which have the function of sensing flow field are used to realize the monitoring of flow field.The measured aerodynamic parameters are provided to the atmospheric computer and the control is optimized,which can improve the stability,safety and maneuvering ability of the aircraft.In order to improve the efficiency of the wind speed sensor,the characteristics of piezoelectric effect and fast response of piezoelectric materials are used in this paper.Piezoelectric bimorphs are used as the sensing element and a piezoelectric sensing-system which can sense wind velocity and wind angle simultaneously is established.Then the sensing characteristics of the two model parts of different contour structure are verified through the experiments.The main research contents are as follows:1.In this paper,the wind speed sensing system of piezoelectric bimorphs array is proposed.The mathematical relationship between induced voltage and wind speed of piezoelectric beam under wind excitation is analyzed.And based on COMSOL finite element software,a two-dimensional model of the coupling of piezoelectric flow field is established.Both the calculated results and the experimental results show that there is function of the second order between the induced voltage(zero to peak value)and the wind velocity.The result of the linear relationship is proved through the experiment of single piezoelectric bimorph in a small wind tunnel.However,the single bimorph cannot determine the velocity and direction of the wind at the same time,so multiple bimorphs of array have been used.The functional relationship of each bimorph between the induced voltage(zero to peak value)and the wind velocity is obtained through the experiments.By using this relation and geometric relation,the wind velocity and the direction angle can be calculated.The experimental results show that the sensing errors of the wind velocity and the direction angle are within 6% and 4o,respectively.2.The author designs a piezoelectric sensing system,it's suitable for aircraft structure based on the nose shape of airliner and fighter.The apex angle of the aircraft nose models are 40o and 60o respectively.The piezoelectric bimorph is embedded in the groove of the model to form a cantilever beam.At the same time,the array of four piezoelectric bimorphs are used.This layout has little effect on the aerodynamic characteristics of model.And a test platform for the piezoelectric sensing system is set up.It is found that there are approximate linear relationship with the two times between the root mean square value of the induced voltage(RMS)and wind velocity and direction angle,so it is used as the characteristic value of wind speed.This linear relationship can be used to identify the value of wind velocity and direction.3.A comparative experiment on sensing characteristics of piezoelectric integrated components of two models is carried out on a self-built test platform.The experimental results are as follow: At the wind velocity of 8.1 m/s,the model of 40o apex angle of the maximum and minimum wind velocity sensing error is 4.14% and 0.34% respectively,the direction angle error is 3.78o and 0.31o respectively;At the wind velocity of 8 m/s,the model of 60o apex angle of the maximum and minimum wind velocity sensing error is 2.38% and 0.5% respectively,the direction angle error is 2.37o and 0.55o,respectively.At the same time,the quantitative relationship between sampling time and sensing accuracy is tested.The sensing time of the wind velocity and direction of the piezoelectric sensing system is within 1 s,the system realizes the real-time perception of the external flow field of the aircraft.In summary,the piezoelectric wind speed sensing system designed in this paper can achieve fast perception of wind velocity and direction within 1 s in the model.The highest sensing accuracy of wind velocity and direction angle is 0.34% and 0.31o,respectively.This lays the foundation for the miniaturization,integration of the piezoelectric system and the real flight sensing experiment of the aircraft in the future.