Research On Flow Control System Of Solid Fertilizer Assembly

To realize precision agriculture,precision variable rate fertilization is a very important step.Precise variable fertilization not only saves planting costs,but also protects soil.To realize precise variable rate fertilization,it is necessary to intelligently apply fertilizer into the soil,so as to improve the utilization rate of fertilizer and solve the problem of poor uniformity of artificial fertilization.Realizing precision variable rate fertilization also puts forward higher requirements for fertilization control methods.Studying better fertilization control methods is an important way to realize precision variable rate fertilization.In order to solve the problem that the filling performance of the ditch in the fertilizer discharger will change with the speed of the discharging shaft and result in the decrease of fertilization accuracy,this paper referred to the current research status of variable fertilization at home and abroad,put forward a fertilizer flow control method,designed a fertilizer flow detection module,and designed a solid fertilizer flow control system based on fertilizer flow detection module.Tests were carried out,the main research contents are as follows:(1)In order to realize the accurate detection of the flow rate of solid fertilizer,a fertilizer flow detection module was designed.Through the optimum design of spiral capacitor plate structure,the influence of edge effect of electric field in capacitor plate measurement was reduced and the detection accuracy was improved.The integrated design of capacitor plate,PCB circuit board and fertilizer guide tube reduced the influence of parasitic capacitance and stray capacitance on test results.According to the requirements of small capacitance acquisition and small acquisition cycle,the corresponding detection circuit was designed.Finally,the bottom program of the fertilizer flow detection module was designed.(2)The fertilizer flow control strategy based on sectional PID was studied.Firstly,the mathematical model of fertilizer discharge per rotation and the fertilizer flow rate of the external trough wheel type fertilizer discharger were determined,and the shortcomings of traditional fertilization methods were pointed out.The sectional PID control strategy based on fertilizer flow feedback was studied and a sectional PID controller was designed.The flow control system of solid fertilizer assembly was modeled and the parameters of sectional PID were optimized.The simulation comparison test between piecewise PID controller and traditional PID controller was carried out,and the piecewise PID controller has stronger adaptability.(3)The flow control system of solid fertilizer assembly was designed.The system mainly includes the main control module of vehicle terminal,can communication module,fertilizer flow detection module,Hall speed measurement module,fertilizer discharge shaft drive control module and power supply module,and each part of the system was designed in detail.Finally,the software of solid fertilizer flow control system was designed,including control system program design and interactive interface design.(4)Modeling and verification test of fertilizer flow detection module and performance verification test of fertilizer flow control system were carried out.A fertilization test rig was built and the model fitting and verification test between fertilizer quality and capacitance integral value was completed on the test rig.The result showed that the maximum detection error of the fertilizer flow detection module was 1.20%.In order to ensure the detection accuracy of fertilizer detection module at different ambient temperatures,the method of adding temperature compensation coefficient was put forward,which finally reduced the maximum detection error of fertilizer flow detection module to0.93%.The performance verification experiments of the solid fertilizer flow control system were carried out on the fertilizer application test stand and field respectively.The results showed that the average accuracy of the overshoot,steady-state error and fertilizer application control of the fertilizer flow control system were 0.64%,2.82% and 98.14%respectively.The precision of field fertilization control can reach 97.81%.The solid fertilizer flow control system met the performance requirements of the fertilization system.