Design And Experiment Of Granular Fertilizer Detection Device For Oilseed Rape Direct Seeding

Excessive application of chemical fertilizer has become one of the important factors of agricultural surface source pollution,and precise fertilizer application is an important means to achieve agricultural surface source pollution management,while online detection of fertilizer application is the key to achieve precise fertilizer application.In order to solve the problem of difficult real-time detection of granular fertilizer in the direct fertilization operation of rape,this paper carries out the research of granular fertilizer detection device for rape direct applicator.Based on the principle of non-contact capacitive detection,the method of using infrared laser diode to provide detection in the time domain and combining with digital signal processing technology,a set of granular fertilizer detection device for rape direct seeding machine was designed to provide a feasible method for realizing realtime detection of granular fertilizer row application,and the main research contents and results are as follows:(1)The structure of the granular fertilizer detection device based on the capacitance method was designed.According to the physical characteristics of granular fertilizer,a time-domain capacitance detection method coupling photoelectric method and capacitance method is proposed based on the principle of capacitive sensing of granular fertilizer,and the structure of detection device consisting of through-fertilizer tube,capacitance shielding box and circuit fixing box is designed,and the mathematical model of capacitance sensor sensitivity is established.Based on Shannon’s sampling theorem and electromagnetic shielding principle,the capacitive pole plate size and pole plate spacing were designed,and the key parameters of sensing components and shielding device materials and parameters were determined.In order to investigate the accuracy and feasibility of the theoretical model,ANSYS Maxwell-based electric field capacitance simulation test and EDEM granular fertilizer pass-through test were carried out.The test results show that the mass flow rate of granular fertilizer has a linear relationship with a goodness-of-fit of 0.997 with the change in capacitance value;the detection device will not be blocked under the condition that the granular fertilizer flow rate of rape is lower than 30g/s(the standard of single-way fertilizer application flow rate of rape directing machine is 5.4g/s～25.9g/s).(2)The granular fertilizer flow signal acquisition and processing system of the detection device is designed.The system converts the capacitance signal when the granular fertilizer passes through the capacitor pole plate into a digital signal that can be directly recognized by the microcontroller,and converts it into granular fertilizer flow information according to the capacitance change value and the granular fertilizer flow model to realize the simultaneous acquisition and processing of granular fertilizer flow signal.In order to obtain the granular fertilizer detection model,the relationship between motor speed and fertilizer flow rate of fertilizer discharger was tested,and the relationship between motor speed and granular fertilizer flow rate with a goodness-of-fit of 0.9947 was established;the relationship between capacitance change value and granular fertilizer flow rate was tested,and the relationship between capacitance change value and granular fertilizer flow rate with a goodness-of-fit of 0.9995 was established.(3)Bench and field tests of granular fertilizer detection device for rape direct seeding machine were carried out.In order to verify the detection performance of the testing device for granular fertilizer,a blind signal test of the photoelectric switch of the testing device was carried out,and the results showed that there was no blind detection area of the photoelectric switch of the device;a bench test of constant flow rate and variable flow rate of the testing device was carried out,and the results showed that the detection accuracy of the granular fertilizer flow rate was not less than 89.63%in the range of 5g/s～30g/s,and the device operated stably without blockage;a bench test of the adaptability of the testing The results show that the device can adapt to other granular fertilizer testing such as Stanley compound fertilizer and Ezhong compound fertilizer;on the basis of this,the field test of granular fertilizer testing device was carried out,and the test results show that the detection accuracy is not less than 85.74%within the range of 10g/s～30g/s for granular fertilizer flow,and the testing device is not affected by light,vibration,dust,etc.during the field test.The test results showed that the detection accuracy was less than 85.74%in the range of 10g/s～30g/s.