| In recent years, around50,000t of forage seeds are demanded in China for each year, of which nearly40percent is depended on foreign imports. Lack of self-sufficiency and highly concentrated market structure make the forage industry in China face high market risk, which shows that improving the supply capacity of the domestic forage seeds is urgent. High quality forage seed is the basic condition to expand the forage reproduction and is also an important material basis to improve degraded grassland, construction of artificial turf, and improve livestock productivity in China. Seeds after processing can improve the germination rate and clarity, which also maintains good vigor. And the process of forage seed can’t be ignored. Mechanization means are necessary preconditions during seed processing. Therefore, the use of advanced technology and machinery equipment for the harvesting and processing of forage seed is the way to achieve the mechanization and industrialization of forage seed processing.Firstly,"Zhong-Mu-Yi-Hao" alfalfa seed which is widely planted in north China was harvested in2014and used the study. The physical and mechanical properties of the alfalfa seed including:grain weight, bulk density, grain density and moisture content were researched and their values were:1.78g,0.779g/cm3,0.98g/cm3, and7.07%, respectively. The flowbilities, suspension rate and recovery coefficient of the seed were shown. The friction coefficient of alfalfa seed and polished metal surface was0.124and their adhesion strength was4.130kPa. Internal friction coefficient and bond strength of Alfalfa seed was0.191and4.406kPa, respectively. Suspension velocity of Alfalfa seed ranged from3.74m/s to5.03m/s and the recovery factor was0.63.By studying the formation of projectile-type screening theory and statistical screening, vibration frequency, amplitude and vibration direction angle which all affected the screen surface vibrations were analyzed systematically. The screening process is that seed overcomes mutual adhesion among particles and between particles with the sieve. EDEM software was introduced to simulate the stratification and passing through the sieve of alfalfa seed during screening process. The results showed that the optimal parameters for selection screen were:the vibration frequency6Hz, vibration direction angle30°, and vibration amplitude6mm, respectively.Then, the processing technology, theory, composition and transmission of small seed sorting machine were analyzed, based on which the hardware components of automatic control systems of alfalfa seed sorting were selected. As FPGA designed as core, vibration feed hopper, hardware screen box, air flow regulator and other agencies of automatic control system were designed, respectively, according to their automatic control process. Based on the hardware platform, through interactive interface, and in the form of user input system to achieve automatic control process, the control system software was design. The software was made for functional building, module division, the overall structure of the program, input and output interfaces, and other operating aspects, respectively. Automatic control software system of alfalfa seed sorting machine was completed from BSP configuration, function panel driver, and interface presentation of WindML, respectively.Finally, based on the theoretical analysis of projectile screening and analysis of simulating alfalfa seed’s motion under different parameter settings screen surface, alfalfa seed sorting and processing machine was tested. According to the key parameters setting of small seed sorting machine and comparing sorting quality of alfalfa seeds under the different vibrational frequency level, the reliability of parameters selection of computer simulation were verified and technical basis was made for the sorting and processing of alfalfa seed. |
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