| Precision agriculture is the only way for the development of modern agriculture in China.It plays an important role in saving resources,reducing costs and improving economic and social benefits.Seeding machinery is an important part of agricultural machinery,the working performance of the seeder has a great impact on agricultural production,it is an urgent need to develop high quality seeding machine in our country,and the seed metering device is the core part of the seeding machine.Therefore,the seed metering test-bed has become an important means for the research and development of high quality planter,it can not be limited by the location,environment,season,and it can improve the repeatability and economy of the test,shortens the development cycle.In this paper,a centralized type pneumatic conveying seed metering test-bed is designed based on the combination of pneumatic seeding principle and electric control technology.Specific work as follows:(1)A centralized type pneumatic conveying seed metering test-bed was developed.The test-bed mainly includes the centralized and quantitative seeding system,one-step distributing system of airflow,seeding control system and the seed metering system.The centralized and quantitative seeding system has a large adjustment range,which can realize the “one device and multiple row” type seed metering;The structure and parameters of the one-step distributing system of airflow were designed and calculated,and the flow field of the one-step distributing system of airflow was analyzed by using the fluid dynamics simulation software ANSYS Fluent,so as to improve the design.The seed-metering device was driven by a stepper motor to realize the control and regulation of seeding quantity;The seed metering system can detect the seeding quantity of each seeding tube,in order to collect and feedback the information of the seed metering.(2)Designed lower computer software.Selected the STM32 microcontroller,stepper motor,pressure sensor,converter and other major hardware,with Keil as the software development platform,wrote the lower computer software based on the C language.In the seeding control system,the speed of the seeding shaft and the the working length of seed-metering device were driven by the stepper motor,the program includes motor driver subroutine,delay procedures,etc.The seed metering system is based on single chip microcomputer,with pressure sensor and A/D converter chip HX711,which can collect andfeedback the information of seed weight.The programs include AD acquisition subroutine,port initialization subroutine,and the subroutine to read seed weight,etc.(3)Designed laboratory test.It mainly includes the total output stability experiment,the test of seeding uniformity per line,the test of seed breakage rate,the test of the relationship between the weight of the seed discharged and the working length of the seed-metering device,etc.The results of laboratory tests showed that the variation coefficient of the total output stability of the test-bed was less than 1.2%,the breakage rate of wheat seed was less than0.5%,the seeding uniformity per line was the best when the length of the corrugated pipe was about 20 cm,the weight of seed discharged was linear with the working length of the seed-metering device. |
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