| Maize is the world’s most productive crop,and China’s maize planting area reaches43.07 million hectares in 2022,and there are problems such as excessive fertilizer application,low utilization rate and serious bias application in the production process.Variable fertilizer application technology formulates fertilizer application strategy based on plant-soil fertility supply and demand relationship,and realizes high quality application of fertilizer through variable fertilizer machine to achieve the purpose of increasing efficiency and reducing application.However,at this stage,variable fertilizer application machine still has problems such as small adjustment range of fertilizer application amount and poor uniformity of fertilizer application.In this paper,we aim to develop a variable fertilizer application device to optimize fertilizer application working parameters and improve fertilizer uniformity to provide some support for promoting variable fertilizer application to achieve accurate operation in corn.The details and conclusions are as follows:(1)Physical property tests of fertilizer granules.In order to provide basic data for establishing an accurate simulation model of fertilizer particles,experiments were conducted on the physical characteristics’parameters of fertilizer particles,such as density,angle of repose,elastic modulus,etc.,using urea,diammonium phosphate,and composite fertilizers as objects,using drainage,injection,and bending methods.The test results show that the sphericity of the three fertilizer granules is above 90%,and the overall shape is ellipsoidal;the highest particle density of diammonium phosphate is 1.592 g/cm~3;the elastic modulus ranges from 185.265-236.563 MPa;the rest angle ranges from 21.76-31.52°,which meets the material fluidity requirements.(2)The overall scheme of corn variable fertilizer application device and its control system design.According to the performance and design requirements of corn variable fertilizer application device,different solutions were compared and the slide-slot linkage type variable fertilizer application device solution was selected.According to the overall scheme and main technical parameters of the variable fertilizer application device,the variable fertilizer application control system scheme is determined,and the STM32F103ZET6 processor is used as the core,and the L298N motor drive module,wireless communication module and power supply module are used to realize the control of the working length of the outer groove wheel and the speed of the fertilizer discharge shaft to meet the requirements of the variable control system of the device.(3)DEM-based design and test of fertilizer discharger structure parameters.Taking the external groove wheel type fertilizer discharger as the research object,the EDEM discrete element simulation software was used to conduct a three-factor five-level orthogonal simulation study with the effective working length of the external groove wheel,the rotational speed of the fertilizer discharge shaft and the groove radius of the groove wheel as the test indexes,and the test results were analyzed by CCD response surface method and parameter optimization design,and the test results showed that the maximum fertilizer discharge volume was 89.430 g/s;the minimum fertilizer discharge volume was 12.922 g/s.The test results showed that the maximum fertilizer discharge capacity was 89.430 g/s;the minimum fertilizer discharge capacity was 12.922 g/s,and the fertilizer discharge capacity of the device could be ensured with the radius of the groove of the outer groove wheel of10.0-10.5 mm under the interaction of various factors.The simulation test results were verified by the test rig,and the maximum and minimum fertilizer discharge errors were4.98%and 6.84%respectively,indicating that the simulation test is highly reliable.(4)Variable fertilizer application bench test and validation test.A bench validation test was conducted with the developed variable fertilizer application device.A three-factor,five-level orthogonal test was conducted with the speed of the fertilizer discharge shaft,the working length of the slotted wheel and the driving speed as the test factors,and the coefficient of variation of fertilizer discharge uniformity and the fertilizer discharge volume as the test indexes.The test results showed that when the target fertilizer application volume ranged from 600-750 kg/hm~2、750-900 kg/hm~2、900-1050 kg/hm~2,the working length of the outer groove wheel was 39.7 mm,44.1 mm and 45.0 mm,respectively,and the rotational speed of the fertilizer discharge shaft was 38.3 r/min,38.2 r/min and 41.2 r/min,and the forward speed The coefficient of variation of fertilizer discharge uniformity was13.78%,13.51%and 13.47%;in order to verify the results of the bench test,the verification test was conducted,and the coefficient of variation of fertilizer discharge uniformity under three working parameters ranged from 14.06%to 14.31%,which was in line with the requirements of the relevant national standard,and the maximum error of the coefficient of variation of fertilizer discharge uniformity and the amount of fertilizer discharge was 5.03%.The maximum values of the coefficient of variation of fertilizer discharge uniformity and fertilizer discharge volume were 5.03%and 4.26%,which indicated that the bench test had high reliability and the discharge capacity and fertilizer uniformity of the variable fertilizer application device meet the design requirements. |
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