Design And Experiment Of The Control System Of The Variable-rate Liquid Fertilizer Applicator

Precision variable-rate fertilization is an important development direction of today’s agricultural production operations.The research on monitoring and realizing feedback control based on geographic location information,soil information,working conditions of fertilizer applicators,etc.has been studied and analyzed by scholars from various countries,and at the same time,it has been put into production through enterprises.Selecting the application of liquid fertilizer can also effectively solve the problems of low absorption rate of solid fertilizer and large environmental pollution.At the same time,in view of the lack of research on the liquid fertilizer flow control system based on electric proportional valve in China,with the main goal of improving the fertilization accuracy and control effect of the boom spray variable-rate fertilizer machine,a PID control method based on algorithm optimization is proposed to make the flow rate Control meets actual usage needs.The main work of this thesis is as follows.(1)Analysis and formulation of the overall scheme of the control systemThe structure of the variable-rate fertilizer applicator is analyzed,and the overall design plan is formulated according to the survey results of Xinjiang cotton fields and the analysis of fertilization control requirements.It can realize variable-rate fertilization in which the flow rate changes with vehicle speed and geographic location information,and determine to optimize the control process of the electric proportional valve,improve the response speed of the control output and reduce the error of the control output.(2)Software and hardware design of variable control systemAccording to the overall design scheme of the control system,the hardware parameters of the control system are calculated and selected,so that the hardware parameters can meet the fertilization requirements.And the fuzzy PID algorithm,BAS-PID algorithm and GA-based fuzzy PID algorithm of the flow control system are designed to optimize the output control quantity of the control system.The three algorithms are simulated and compared through MATLAB software,and the results show that the BAS-PID algorithm has the best optimization effect on the control system.Therefore,the basic fertilization software functions are designed,and the BAS-PID algorithm is used as the core program of the control system software design to improve the effect of variable speed flow control.(3)Control system bench testThe test platform is built based on hardware selection,the basic functions of the system are tested,and the system response performance and variable-rate fertilization accuracy are tested.The results show that the average relative error of system flow is 1.27%,the maximum absolute error is 0.64 L/min,and the average response time of variable flow control is 2.0 s under the PID tuning method based on the beetle antennae search algorithm,which meets the requirements of actual fertilization.