Experimental Research On Variable Rate Spraying System In Agriculture

The thesis takes the research of the working accuracy and the influencing factors of variable rate sprayer system used in agriculture. The experimental platform to test the system was set up on the basis of SCS450 sprayer control system manufactured by Raven Industries, Inc. The platform can be used to test every nozzle's flow rate variation and the consistency of uniformity across the boom section accordingly. It can also be used to test and study sprayer rate error at constant and variable application rates by the instrument of turbine flow rate sensor. Consequently the method of reducing sprayer rate error of variable application was concluded. Another test was performed to study the factors influencing sprayer distribution uniformity as well as the influencing law. At the end statistical correlation and regression analysis of factors influencing sprayer distribution uniformity was undertaken.Coefficient of variation was used to evaluate nozzle flow rate variation and its consistency of uniformity across the boom section in order to deduce uniformity of all booms which actually control nozzles. Comparing coefficient of variation of nozzle's flow rate in the width, the maximum one is less than 4%; comparing coefficient of variation of single nozzle's flow rate in different duration, 98% coefficient of variation is less than 6%. Therefore not only booms could control the variation of flow rate and maintain the consistent flow rate, but also the system can apply uniform chemical rates under different nozzles, durations and pressures.The results of study revealed that sprayer rate error at constant application rates was low, normally less than 5%. Because of the existence of transport lag, system could not apply uniformed rates during lag phase, therefore increasing overall rate error. The negative effect on sprayer rate accuracy caused by transport lag could be reduced by lowering vehicle velocity or by presetting 1 second look-ahead time as crossing the border, consequently reducing the overall rate error.Finally the effect on sprayer distribution uniformity of nozzle pressure,height, installation angle and type was studied and therefore the best conditions for variable spraying could be chosen. Increasing nozzle height could improve distribution uniformity within a limited range. In order to acquire better uniformity the height must be over 40cm. Nozzle type also has effect on sprayer distribution uniformity, the nozzle...