Design And Experiment Of Sowing Amount Control And Seeding Monitoring System For Rice Direct Seeder

Rice direct seeding is a convenient cultivation technique that has been rapidly developed and expanded in recent years.It has the advantages of saving labor,saving cost,reducing the amount of labor,and facilitating mechanized operation on a large scale.Under the current situation of labor shortage in rural areas,scarcity of water resources in the paddy field,and increasing cost of labor,rice direct seeding can solve the problem of insufficient rural labor resources and promote sustainable rice production,which is of great significance to promoting agricultural efficiency and increasing farmers’ income.However,the existing rice direct seeder has a simple functional structure,a low degree of automation,and a relatively extensive seeding operation.The ground wheel drive seed metering method is generally adopted,the sowing quantity adjustment is complicated,the synchronism is poor,and the ground wheel slippage is liable to cause uneven seeding.The seeding process lacks real-time monitoring means.In case of blockage and leakage,it is easy to cause losses,which affects the seeding quality of rice direct seeding machinery.In view of the above problems,this study designed the sowing volume control system and seeding monitoring system for the rice direct seeding machine to improve the intelligence level of the rice direct seeding machine.The specific research contents are as follows:(1)Automated transformation of the existing rice direct seeding machine,changing the traditional ground wheel drive seeding mode,using DC motor to drive the seeding shaft;comparing and analyzing through five kinds of speed measuring methods,designing the contouring speed measuring wheel,selecting the encoder speed measuring to collect the rotation speed of the seeding shaft and the measuring wheel,designing and installing the mechanical components of the seeding quantity control system.(2)Designing the seeding quantity control system.The seeding quantity control system is constructed with modular design concept.The hardware system uses STC12C5A60S2 single-chip microcomputer as the main controller,IRLS3036 MOS tube to build DC motor drive,400-line encoder to form speed collecting module,key switch and digital tube display to construct man-machine interactive module.The 10A plug-in fuse constructs an overcurrent protection circuit;the software system mainly constructs a functional relationship between the target seeding amount,the seed-metering motor speed and the machinery vehicle speed according to the synchronous seeding control principle,which realizes that the seeding speed responses to machinery vehicle speed synchronously.The PID control algorithm is introduced to establish the DC motor rotation speed PID control model and design the corresponding PID controller to realize the closed-loop control of the seed rotation speed,optimize and improve the control accuracy of the seed rotation speed,and improve the control system’s ability to adjust the load change.(3)Designing a seeding monitoring system.According to the physical properties of the capacitor plate,the capacitive seeding monitoring system is designed.The STM32F103C8T6 single-chip microcomputer is used as the main controller to design the capacitive plate monitoring sensor.The PCAP01 chip is used to build the plate capacitance detection circuit.The 4pF reference capacitor is selected to realize the 10-13F weak capacitor.The mathematical models of seeding discharge and capacitance value are established by fitting test,and the detection and alarm strategies of target seeding quantity and measured discharge are constructed.When the system works,the real-time seeding amount can be displayed,and the seeding status can be judged according to the detection alarm strategy to realize the fault alarm.(4)Test design of the seeding quantity control system.Through the bench test,different speed control tests are carried out to determine the overshoot,peak time and adjustment time parameters of the seed-metering motor;the variable drive load response test is carried out,and the actual seed metering of the shaft is simulated by applying different loads,and the test record controls the parameters of different load callback time and load current;through the field test,the seeding volume control accuracy test is carried out to test the control effects of different seeding quantities at different speeds,and the rotational speed error and the seeding quantity error parameters are recorded during the test;The synchronous response test of seeding was carried out to explore the synchronous response effect of seeding quantity control system.During the test,the speed of planting axis and measuring wheel was recorded by collecting card,and the synchronous response curve of planting speed was drawn.(5)Test design of seeding monitoring system.Carry out the calibration test of seed flow and plate capacitance difference,determine the difference data of different seed flow and capacitance and fit the mathematical function through MATLAB;carry out the test of the accuracy of the seeding quantity monitoring under different speeds,measure the difference of 20s capacitance and the actual seeding quantity data,Calculate the error between the target seeding volume and the actual seeding volume;carry out the monitoring and alarm test to test the alarm accuracy of the monitoring system by means of artificial simulation of seeding blockage and missed seeding fault,and the alarm data was recorded for 20 times respectively.The test results show that the adjustment peak time of the seeding control system is small at different speeds,the overall adjustment time is lower than 0.63s,and the response is timely;when the load of the motor is increased,the instantaneous speed of the motor is gradually decreased,and the adjustment time is adjusted.When the maximum load is 12.5N·m,the system speed callback time is 0.32s,the load current is 6.5A,the control system responds quickly,the control system works stably under large load operation conditions,and the performance is reliable.The field test results show that in case of target seeding,the maximum speed control error is 7.21%,the maximum seeding error is 3.96%,the seeding speed and the seeding amount are controlled accurately,the response of field seed metering rotation speed is timely,and the seed synchronization performance is good,which can meet the actual demand.The linear measurement coefficient of the capacitance plate and the seed flow fitting function of the seeding monitoring system is R2=0.9723,which has a high linearity;the maximum average error of the theoretical seed flow and the actual seed flow is 4.51%.When planting quantity increases,the monitoring error tends to decline,and the monitoring accuracy of the monitoring and control system is relatively stable and accurate.Under artificial failure test,the success rate of monitoring and alarming is 100%,which can be used for actual seeding monitoring.The seeding quantity control system and the seeding monitoring system have high applicability to the traditional rice direct seeding machine,improve the intelligence of the existing machine tools,improve the seeding quality,and provide reference for the automatic transformation of the rice direct seeding machine.