Design And Research Of Air-Suction Wheat Precision Seeding Device Based On PWM Electro-Hydraulic Proportional Control

Precision sowing and precision fertilization are the development direction of agriculture in the future.Air-suction wheat precision seeder is the most precise sowing machine in the existing precision seeder.However,there are still some problems such as seed leakage(fertilizer)caused by wheel skidding,leakage sowing caused by power output stopping when tractor stops or turns,and out of control when motor speed is high.Aiming at the existing problems of air-suction wheat precision seeder,this paper takes the air-suction wheat seeding device controlled by PWM electro-hydraulic proportional control as the research object,makes a full study of its operation mechanism and internal principle,establishes the model of electro-hydraulic proportional control system based on PWM and the geometric model of vertical double sucker metering device.The research focuses on the following three aspects.(1)Design of PWM electro-hydraulic proportional control system.The PWM electro-hydraulic proportional control system is designed through the self-designed hydraulic station and the selection of electro-hydraulic proportional control related components.The system takes STM32 as the control core,collects the tractor's forward speed and the rotation speed of the fertilizer-metering axis in real time,adjusts the rotation speed of the fertilizer-metering axis in real time with the PID control algorithm,matches the tractor's forward speed accurately,guarantees the stability of the planting spacing and the uniformity of fertilization,and realizes the intelligence of the air-suction wheat precision sowing device by real-time monitoring through touch screen in the process of sowing and fertilization control.(2)Modeling and simulation analysis of PWM electro-hydraulic proportional control system.According to the self-designed PWM electro-hydraulic proportional control system,taking seed metering drive as the research object,the model of electro-hydraulic proportional control system based on PWM is established by using AMESim software.The feasibility of the design of electro-hydraulic proportional control system and the rationality of the selection of hydraulic components are verified by simulation experiments.(3)Gas-solid two-way coupling simulation analysis of air-suction metering device DEM-CFD.Geometric model of metering device and grain model of wheat were established by Pro|Engineer software and STAR-CCM+software respectively.The performance of vertical double sucker metering device was simulated and analyzed by using pressure priority control and speed priority control respectively by STAR-CCM+software.The results show that the best seed metering effect is obtained when the rotation speed of the seed metering shaft is 70 r/min and the pressure of the air suction chamber is-2.5 kPa.The simulation results are further confirmed in the prototype test.According to the analysis of the fertilization experiment of the prototype,it was found that when the PWM electro-hydraulic proportional drive controlled the fertilization axis,its speed response time was fast,running smoothly,the coefficient of variation of the stability of the seeding was less than 2.95%,and the coefficient of variation of the stability of the fertilization was less than 3.99%.