Research On Monitoring And Control System Of Threshing And Clearing For Maize Combine Harvester

The threshing and cleaning device is the key device of maize combine harvester,which determines working performance and efficiency of harvester.Due to adverse and varied field environment,working performance of the threshing and cleaning device can not be fully exerted,which cause high grain breakage rate and loss amount,and cause threshing cylinder to be blocked easily.In this paper,the main factors influencing effect of threshing and cleaning are analyzed according to characteristics of nonlinear,time-varying and lagging in working process of threshing and cleaning device.On this basis,PLC as core controller,touch screen for monitoring and control interface,the monitoring and control system of threshing and clearing are developed.Through monitoring and control system,the key parameters is monitored and early warned,and the hydraulic actuator parameters is adjusted.The operating speed variation is got through fuzzy control,so the walking speed is adjusted,which can make threshing and cleaning device give full play to working performance under premise of ensuring reliability.The principle of threshing and cleaning is studied,and the main factors influencing effect of threshing and cleaning is analyzed,which includes threshing cylinder rotation speed,threshing gap,feeding rate,grain moisture content,air volume of fan and outlet angle,vibration frequency and amplitude of clearing sieve box,opening of chaffer,etc.In view of these factors,the amount of monitoring and control is determined,and then the overall scheme of monitoring and control system of threshing and clearing is established.The fuzzy control principle and algorithm is studied.Two-dimensional fuzzy controller of threshing cylinder is designed,which the angular velocity deviation and variation rate of cylinder is input,and the variation of harvester walking speed is output.The fuzzy inference rules and fuzzy control query table is developed combined with actual control experience.The fuzzy control algorithm is used to control threshing cylinder load.The hardware system is designed according to monitoring and control system scheme,which mainly includes selection and layout of moisture sensor,pressure sensor,and dynamic torque sensor,detection and adjustment of harvester walking speed,threshing cylinder rotation speed,fan rotation speed,sieve box driving speed and other key speed,as well as threshing gap.According to system requirements,PLC and touch screen are selected,and PLC input and output terminals are distributed rationally.The software system is designed according to the monitoring and control system process,which mainly includes the ladder program for digital and analog sensors collecting key parameters,controlling hydraulic actuator,realizing fuzzy control algorithm.The man-machine interface of touch screen is developed to achieve functions of setting initial parameter,acquiring and displaying key parameter,controlling hydraulic actuator and alarm.The threshing cylinder fuzzy controller is designed by using MATLAB Fuzzy Logic Toolbox.The cylinder fuzzy control model is established and simulated by Simulink.The simulation result shows that fuzzy control algorithm is feasible for control of cylinder load.The monitoring and control system of threshing and cleaning experimental platform is set up for experiment to imitate key parameter acquiring,monitoring and early warning,and controlling hydraulic components.The experiment result proves that the monitoring and control system is rational and valid.