| Fertilization can improve soil nutrients and increase agricultural output.Large machineries are difficult to apply in southwest hilly mountain area of China,the fertilizer apparatus have horizontal spiral conveyor or outer groove-wheel are common.The characteristics of fertilizers have a great influence on the discharge performance of this kind of fertilizer distributor,situations like fertilizer overhead,blockage etc.often make up "broken bar” phenomenon,and it is difficult to control the amount of fertilizer precision when applying fertilizer.Fertility uniformity of such fertilization equipment is so poor that reduce fertilization quality.Crop fertilization mainly depend on human resources,which are labor consuming and have poor effects.Therefore,it's necessary to develop a fertilizer applicator which can fertilize quantitatively and be widely used in southwest hilly mountain area of China.In order to increase the utilization of fertilizer,reduce the cost,and promote the sustainable development of agriculture.This article has been developed and studied the control system of the quantitative fertilizer applicator considering the situation in southwest hilly mountain area of China.Vertical spiral distributing device is chosen as the distributing system of the fertilizer applicator.Firstly,getting regular rectangular wave signal after filtering and shaping the pulse signal from the Hall sensor,which can measure walking speed.Then,adjusting the voltage at the end of the drive motor to achieve accurate fertilization with the help of a control system in which PIC MCU is used as the main control chip.This paper studied the control strategy of the perpendicular spiral distributing device according to the performance requirements and theoretical analysis.Firstly,mathematical model of the control system was built based on the motion parameters.Then,a series of experiments was conducted and the parameters of the mathematical model were adjusted.Finally,the conclusion was expressed that fertilizer consumption of the fertilizer applicator is proportional to the speed.DC gear motor was selected as the driving mechanism of the vertical spiral distributing device.Closed loop control was adopted for output speed and input voltage of the motor according to the characteristic of a DC motor.Fertilizer consumption in real time was corrected by collecting speed signal and comparing the feedback signal and theoretical speed.In the aspect of hardware circuit design,we utilized PIC18F13K22 as the control chip,used N channel MOSFET tube FDN359 AN and P channel MOSFET tube FDN360 P as power switch of motor control,completed the hardware circuit of the control system of drawing in Protel.MPLAB integrated development environment was used to complete the driver programming and debugging.At the same time,the anti-interference design of both hardware and programs was considered strictly to make the whole system work reliably.The uniformity test and field test had been conducted after debugging the prototype.Test results showed that the control system of the fertilizer applicator met the requirements.Under the condition of regular walking speed of 0.5-1.2 m/s and fertilizer consumption within 300~750 kg/hm2,the maximum coefficient of variation in the uniformity test is 7.06%,and the maximum error of the field test is 6.76%.Therefore,it can be concluded that the fertilizer applicator achieved the design requirements of the technical specification for quality evaluation(NY/T1003-2006). |
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