| Corn is one of the three major food crops in China.Its planting area and total output rank second in the world.Corn is an important food resource and industrial raw material.Its output,quality and reserves are of great strategic significance to national security.In 2020,China’s corn output will be 260.67 million tons,and the planting scale and output will increase steadily.At the same time,higher requirements are put forward for the whole process mechanization of corn"seed management harvest",especially in the corn sowing link,the sowing quality will directly affect the later management and output.Under the background of modern agriculture advocating large-scale production,improving the qualified rate of corn sowing and popularizing corn precision sowing technology are of great significance to realize the whole process mechanization of corn production.At present,the corn precision metering device is mostly driven by the ground wheel transmission mode,and the phenomena of increasing the slip rate,reducing the sowing qualified rate and increasing the missed sowing rate are easy to occur when the planter operates at high speed.This study takes the follow-up performance of the corn planter metering device under the condition of high-speed operation as the starting point,and adopts mathematical modeling,comparative simulation,prototype development,performance test By means of field test,we carried out theoretical and Experimental Research on the control mechanism and monitoring system of air suction maize sowing electromechanical driving seed metering device,and completed the system R&D,selection and commissioning of air suction maize sowing electromechanical driving seed metering device.The main research contents are as follows:（1）Measurement of load characteristics of seed metering device of air suction corn planter:select Vset air suction seed metering device as the research object,develop the load state/parameter detection test-bed,complete the dynamic measurement test of load torque of air suction seed metering device under the conditions of speed increase,uniform speed and deceleration,obtain the load change law of air suction seed metering device under different working conditions,and determine the load torque Selection principle of drive motor based on speed range and output power.Through test and measurement,the maximum torque required for starting and accelerating the air suction seed metering device at 0km/h-15km/h is 1.836N.m and the speed is VN≥390r/min,power P(（9）≥18.37W brushless DC motor as the driving motor of air suction seed metering device,and match Number of gear teeth 18 gear to form the power system of electric drive seed metering device.（2）Control model establishment and Simulation Analysis:using the mathematical model under the double closed-loop control of speed and current of seed metering drive motor of PWM speed regulation system,the speed and current closed-loop speed regulation system of seed metering drive motor is designed.The PWM model of DC brushless motor is simulated in MATLAB software to test the speed change of speed regulation system System stability and response characteristics under load disturbance.The dual-mode control scheme of permanent magnet brushless DC motor is designed,and the operation mode of the dual-mode control system of permanent magnet brushless DC motor is established.The PID control model,fuzzy PID control model and sliding mode variable structure model with SMO are simulated.The performance of the three control models in system response time and stability is tested through comparative experiments.（3）Develop the monitoring system of electric drive precision sowing device:develop the monitoring system of air suction sowing electromechanical drive seed metering device,and realize the real-time data sharing of planter with server and terminal through GSM network.According to the locomotive forward speed and the predetermined sowing spacing data,the monitoring system outputs the PWM signal of the DC permanent magnet brushless motor through the sliding mode variable structure control algorithm,so as to realize the dynamic synchronous control between the forward speed of the planter and the speed of the seed metering device.Develop the upper computer and lower computer software supporting the monitoring system to realize the functions of command transmission,data polling,fault reporting,system start and stop,etc.Develop mobile APP based on Android system to realize real-time sharing and remote monitoring of planter operation data.（4）Research on the main performance of the monitoring system:analyze the response time of the monitoring system of the pneumatic seeding electromechanical drive seed metering device,measure the response time of the monitoring system by monitoring the time difference between the forward speed of the locomotive and the synchronous speed of the electric drive seed metering device,and analyze the main causes of the delay.The test results show that the overall follow-up performance of the monitoring system of the electric driven seed metering device is good,the average deviation is about 3.19%,and the deviation is the largest when the monitoring system is started.The power consumption of electric seed metering device was tested,and the working time measurement of seed metering device driving motor under different working conditions was designed.The test results show that the power consumption of the electrically driven seed metering device is directly proportional to the operating speed of the planter and inversely proportional to the negative pressure of the seed metering device.In the test,the maximum power consumption occurs when the operating speed of the planter is 12km/h and the negative pressure of seed filling is 3k Pa.The maximum power consumption of the system is15.48W.The static power consumption of electrically driven seed metering device is within the range of 3.86W.（5）Field experiment:using the self-developed 2-rows air suction electric driven planter,taking the grain spacing qualification index,standard deviation and coefficient of variation as the test indexes,the sowing spacing comparison test of electric driven seed metering device and ground wheel driven seed metering device under low,medium and high speed conditions is carried out to verify the overall performance of electric driven seed metering device.The experimental results show that the measured sowing spacing of electric driven seed metering device under different working conditions is 17.6cm-33.5cm;The sowing spacing of the ground wheel driven seed metering device is 12.6cm-45.0cm;The standard deviation of sowing with electric drive seed metering device is distributed between[1.49-2.65],and the standard deviation of sowing with ground wheel drive seed metering device is distributed between[1.49-5.87].Under working conditions,the sowing variation coefficient of electric driven seed metering device is between 6.00%-10.42%,and that of ground wheel driven seed metering device is between 7.40%-22.18%.Under the condition of high-speed operation,the sowing qualified rate,average sowing spacing,standard deviation distribution and coefficient of variation of electric driven seed metering device are better than those of ground wheel driven seed metering device. |
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