Design And Experiment Of Liquid Quantity Monitor For Pesticide Tank In Spraying UAV

The liquid-quantity data is one of the most important information to flying operators of spaying UAV.During the aerial spraying,the liquid-quantity in the pesticide tank is dynamic,the flying operators have always to paid attention to the liquid-quantity so that they can make suitable decisions for the flight controlling.Therefore,the liquid quantity monitoring method for pesticide tank is most important in UAV spraying.However,there are lots of special characteristics to achieve real-time monitoring the amount of pesticide liquid of spraying UAV,including liquid surface violent fluctuation,different physical and chemical properties in different pesticide,different shape of different tank,the higher anti-corrosion requirements and the size of tank is too small,etc..This paper aimed to explore the feasible method for liquid-quantity monitoring of pesticide tank in spraying UAV.Based on the above characteristics,this paper puts forward a solution,which called dual-pressure liquid-quantity monitoring,including a double pressure sensors for liquid-level monitor,wave filter for liquid-level turbulence(which is a combination of the median filter and the moving average filter),liquid-level correction for aircraft on a tilt(based on a MEMS gyroscope),and conversion model for liquid-level and liquid-quantity.In order to verify the feasibility of the proposed solution,a prototype of liquid monitoring device was developed,and the relevant verification test was conducted to test its performance.The experimental results showed that there is significant linear negative correlation between the liquid-level and pressure difference(between ambient atmospheric pressure and sealed air chamber pressure caused by liquid level),and the correlation coefficient R~2 is 0.9989.It is indicated that the dual-pressure method can effectively eliminate the influence of ambient atmospheric pressure changes on the measurement accuracy and stability.By using the proposed wave filter,the C.V.(coefficient of variation)of liquid level data decreased from 28.45%to 12.27%.It is obviousthat the proposed wave filter can filter off the liquid-level turbulence effectively.By using liquid-level correction for aircraft on a tilt,the relativeerror reduced to 0.59%from 12.93%when the aircraft tilt up to 30°.It is indicated that the proposed tilt correction method can effectively eliminate the error caused by aircraft body tilt.In order to test the performance of prototype of liquid-quantity monitor in the actual spraying operation,the test based on a spraying UAV,3WDM4-10 and TXA-616,wereconducted.It included three different flying attitudes,forward,backward and turn around at the edge of field.When the payload of the pesticide tank was 2 L,4 L and 6 Lin 3WDM4-10,the relativeerror out by the liquid-quantity monitor were 0.75%、1.45%、0.77%,the RMS error is 0.182L,0.199L and 0.180L respectively.When the payload of the pesticide tank was 2 L,4 L and 6 L in TXA-616,the relaiveerror out by the liquid-quantity monitor were 0.45%、0.30%、0.33%,the RMS error is0.030 L、0.032 L、0.031 L respectively.In addition,liquid quantity monitoring test in actual spraying was carried out,measurements showed that the average relative error of3WDM4-10 is 1.64%,the RMS error is 0.069L,the average relative error of TXA-616 is1.23%,the RMS error is 0.024L.The results demonstrated that the output of the proposed liquid-quantity monitor is stable and reliable in different flying attitude.Therefore,The method and apparatus can effectively complete the real-time monitoring the amount of liquid of plant protection tank.In this paper,the feasibility and effectiveness of the scheme is proved,which can provide reference for the manufacture and debugging of the newest prototype.