Design And Experiment Of A Wind Pressure Conversion Near Ground Wind Speed Detection Equipment

In recent years,agricultural aviation in China is in the stage of rapid development.In the application of agricultural aviation,the rotor wind field of agricultural unmanned aerial vehicle(UAV)has an important influence on the application of pesticide and pollination.In the agricultural aerial pesticide application,the wind force of the UAV directly affects the penetration of the droplets.If decomposite the wind field of UAV,the wind in direction of ground has a significant effect on droplet penetration and deposition,the wind on horizon will have great influence on the spray rate,droplet uniformity and droplet drift etc..The power and direction of wind speed will directly affect the distance and density of rice pollen,which is very important to the actual operation effection.In order to obtain the information of the wind field parameters of the rotor in the field canopy,a wind field wind speed detection system was designed and tested.Laboratory analysis and field experiments show that the system can effectively detect the rotor wind speed data of UAV,and provide effective help to the field work of UAV.For wind speed measuring sensor on using,the vane anemometer,it has larger dimensions,its interference to rotor wind field can not be ignored.To solve this problem,this paper based on the pitot tube as the detection element,completed the hardware design and software design of detection node as well as field wind speed detection system design.The system has 10 nodes,each node includes three sets of pitot sensor components,through the circuit design and mechanical structure design,multi point,multi direction or multi gradient,real-time acquisition of wind speed data could be realized.Firstly this paper analyzes the advantages and disadvantages of various wind speed sensors of different principle,and then complete the overall design for the wind field detection system,and the design of hardware and software for t he detecting node based on the conversion principle of wind to pressure.And completed the following experimental analysis:(1)In order to verify the advantages of the pitot tube relative to the vane anemometer in reducing wind speed disturbance,this design adopts the axial fan test system for comparative analysis of the disturbance of both the sense portion of vane anemometer and the sense portion of the pitot tube speed sensor to the flow under different wind speed,the test shows that the pitot tube has significant advantages compared to the vane anemometer in reducing its disturbance to the flow,in the wind speed of 10 ~ 15m/s,wind speed in the direction of the pitot tube detection weakened does not exceed 2%,but due to part of the wind energy convert into kinetic energy,the sense section of the vane anemometer weakened wind speed basically reached more than 20%;(2)Analysed the error sources of pitot tube wind speed sensor and design tests to prove them,and proposed a method to correct the error.Through the error analysis,one of the important section of error sources is wind pressure transmitter,which is components of pitot tube wind speed sensor,designed tests to find out the influence of its pose,and the test shows that the effect is obvious,it ca n change the voltage signal by 3~5m V,should specify the use of wind pressure transmitter with the same pose to install.(3)To compare the consistence of pitot tube wind speed sensors,using the flow fan wind system to detect the pitot tube wind speed sensor.The tests shows that the maximum relative error between the pitot tube wind speed sensors less than 6.40%,the variation coefficient was 1%,the consistency of each sensor to measure the speed of the wind is good.(4)For low pressure under low wind speed,Bernoulli formula is not applicable,causing the error to pitot tube sensor in wind speed detection,this paper completed the fitting optimization of wind-pressure conversion parameters of the pitot tube wind speed sensor under low speed wind speed.After the fitting optimization SSE=0.0996,goodness of fit R-square>0.96,in this fitting way,pitot tube wind speed sensor can still get high precision at low wind speed in which condition wind pressure is low;(5)Compare the difference between the new system and the original system by outdoor test,and conduct field tests to improve its great reliability and sensitivity.