Design And Experiment Of Air-assisted Centralized Fertilization System

Precision fertilization is an important way to improve the quality of fertilization operations and fertilizer utilization efficiency,and is of great significance for achieving green and sustainable agricultural development.This study aims to address the issue of low fertilizer utilization during the fertilization process due to the low uniformity of the external slot wheel fertilizer discharge device and the inability of the ground wheel drive mode to adapt to conditions such as sticky soil or paddy fields.A wind driven centralized fertilizer discharge device and fertilization control system have been designed.Verify the fertilizer discharge performance of the air-assisted centralized fertilizing system using methods such as bench and field experiments.The main research content and conclusions of this study are as follows:(1)An air assisted centralized fertilizer discharge device with the core of"centralized fertilizer discharge+air assisted fertilizer transportation"has been proposed.Based on the working principle of the external groove wheel fertilizer discharger,a spiral groove structure fertilizer discharger was designed,with a fertilization rate of 150-600 kg/hm~2as the design goal and uniform fertilization as the goal,determine that the diameter of the fertilizer discharge wheel is 60 mm,the radius of the circular groove is 6 mm,the effective working length of the fertilizer discharge wheel is 30 mm,and the number of grooves is 12.The spiral rise angle of the groove of the spiral groove fertilizer discharge wheel is 62.4°.According to the particle transportation theory and suspension test,it is known that the optimal conveying air velocity and conveying air volume should be greater than 21 m/s and 375 m~3/h,respectively.It is advisable to select a diameter of 32 mm for the fertilizer conveying pipe.(2)Using EDEM software to simulate the fertilizer discharge process of the centralized fertilizer discharge device,it is determined that the consistency of fertilizer discharge in each row of the spiral groove fertilizer discharge wheel is better,and the coefficient of variation of fertilizer discharge uniformity in the staggered groove fertilizer discharge wheel is the lowest.Conduct bench tests to fully compare the fertilizer discharge performance of the centralized fertilizer discharge device under the action of each groove structure fertilizer discharge wheel.Use the weighting method to determine that the spiral groove fertilizer discharge wheel has the optimal comprehensive fertilizer discharge performance.At a speed of 20-60 r/min,the highest coefficient of variation for consistency of fertilizer discharge in each row,stability of total fertilizer discharge,and uniformity of fertilizer discharge are 2.06%,0.22%,and 3.83%,respectively.The experiment shows that the critical point of fertilizer discharge speed is 96.77 r/min,which meets the requirement of fertilizer discharge accuracy≥95%and achieves the design goal of fertilizer application rate of 150-600 kg/hm~2.(3)A working speed monitoring module composed of an encoder and GPS was designed,combined with a finite amplitude recursive average filtering algorithm to eliminate the impact of instantaneous working speed signal fluctuations and smooth the working speed signal.Road tests have shown that the operating speed monitoring module can monitor operating speeds of 0.77-6.66 km/h.After filtering,the maximum deviation of the average operating speed is 1.64%,and the lag time is between 0.3-0.53 s.The fertilizer discharge motor is matched and selected based on the average static moment of 7.94 N·m and rotational inertia of 6.66 kg·cm~2of the fertilizer discharge device.The fertilization control system adopts a running speed monitoring module,a limited amplitude recursive mean filtering algorithm,and a semi closed-loop control of the fertilizer discharge motor to improve control accuracy and fertilization accuracy.(4)The step response performance test results of motor speed show that the fertilizer discharge motor operates at 200 r/min,the overshoot is 1.69%,the steady-state value is195.89 r/min,the rise time is 0.35 s,the peak time is 0.45 s,and the adjustment time is 0.73s.Build a dynamic test bench to obtain the maximum response time for fertilizer amount adjustment of the fertilizer control system,which is about 0.85 seconds.A field experiment was conducted on air assisted centralized fertilization system.When the theoretical fertilization amount was set at 300 to 600 kg/hm~2and the average operating speed was 5.22km/h,the fertilization accuracy rate under different fertilizer types was>95%.The air driven centralized fertilizer discharge system has good fertilizer control accuracy in various fertilizer application requirements,and can adapt to different granular fertilizers,meeting the requirements of accurate and synchronous fertilizer application operations.