Research On Two-stage Jet On-line Drug Mixing System Based On Fuzzy PID Control

In recent years,pesticides are still widely used in agricultural production,and it is of great significance to adopt scientific and advanced mixing technology for efficient pest control and weed control,guarantee the safety of application of pesticides,and promote the increase of grain yield and income.Compared with traditional premix technology,online blending technology improves pesticide availability and safety for mixers.Aiming at the problems of insufficient uniformity and low pressure ratio in the single-stage jet online mixing technology,this paper designed and adopted a two-stage jet mixer,built the experimental device platform of the mixing system,and carried out the research on the online mixing system under the new control mode.The fuzzy PID control algorithm is used to control the mixing process,which overcomes the disadvantages of the traditional PID control algorithm,such as the trouble of parameter setting and the high requirement of the control system model,and effectively improves the control precision of the mixing ratio,the uniformity of the mixing,and reduces the response time of the control system.The main research contents of this paper are as follows:(1)An experimental platform for two-stage jet online mixing control based on fuzzy PID control was built.The device adopts a two-stage jet mixer,one part of the high-speed water flows through the radiation flow tube of the two-stage jet mixer to absorb the drug liquid and complete the first mixing,the other part enters the main jet mixing tube and absorbs the mixed liquid of the radiation flow tube to complete the second mixing.High-performance GD32F405 microcontroller is used in the control system as the main controller,using fuzzy PID control algorithm to control the peristaltic pump flow,and in the process of control pressure,flow,liquid level,such as data collection,using ZIGBEE wireless communication mode will be to collect data to PC for data analysis and historical preservation,realize remote human-computer interaction.(2)The mathematical model of the control system was established,and MATLAB software was used to simulate the control system model.According to the hydraulic simulation principle,the fluid piping system is equivalent to the circuit conduit model,and the transfer function model between the control system flow rate change and the control system peristaltic pump input voltage change is obtained,and the characteristic parameters are determined by the two-point method.PID and fuzzy PID control algorithms are used to simulate the control system model respectively.The simulation results show that the overshoot of fuzzy PID control is reduced by10% compared with PID control,and the time of the system to reach steady state is reduced by 0.2s.(3)Design parameter optimization and drug mixing performance of the system.Based on drug control system,the total pressure ratio and mixing uniformity of experimental analysis,the two-stage jet mixing drug main jet pipe and auxiliary jet nozzle length of jet pipe,outlet diameter,Angle parameter was optimized,finally choosing main,auxiliary jet pipe jet nozzle length is 41.5 mm and 38.5 mm respectively,the main and auxiliary jet pipe jet nozzle outlet diameter 3 mm,2 mm,respectively,The nozzle angles of the main and auxiliary jet pipes are 16° and 16°respectively.In addition,through the mixing performance experiment,the mixing ratio error is 3.55%,the variation coefficient is 3.76%,and the steady-state time is 0.6s under the fuzzy PID control.Compared with the direct control PWM and PID control,the experimental results show that the fuzzy PID control has smaller mixing ratio error,higher mixing uniformity and faster adjusting speed,which can meet the requirements of online mixing.