EDEM simulation and experiment of pullout force of protected vegetable harvester

Abstract: Although China is a vegetable planting country, the degree of mechanization of vegetable production is low. With the advance of the urbanization and industrialization in China, arable land gradually becomes less, and the vegetable cultivation is paid more and more attention. Facilities vegetable cultivation is an important way for vegetable cultivation. However, the level of mechanization of protected vegetable is lower than 25%, and the comprehensive mechanization level of vegetable production is about 20%, while production of leaf vegetables in China accounts for 30%-40% of total production. Therefore, the development of efficient and stable facilities vegetable harvesting machinery is the premise to achieve the automation of vegetable plantation and production process, and is of great significance to achieve the mechanization of agriculture, especially vegetable production. However, the height of the existing vegetable picking machine can not meet the requirements, for the distance of the rhizome exposed is too short, which leads to the phenomenon that vegetable is cut loose and harvesting fails. Therefore, in this paper, the model of the vegetable harvester is established, and the problem of cutting is analyzed. Based on the analysis of the above and lower parts of the vegetable stem in the process of drawing, the mathematical parameters of the drawing force were analyzed, and the key factors affecting the pulling force of the vegetables were the height of the vegetables and the height slope. Through the tensile test of the rhizome of the vegetable sample and the compression test of the stem of the vegetable sample, the mechanics parameters of the vegetable were obtained, and the necessary theoretical support was provided for the simulation of the drawing of the vegetable and other research. The distinct element method (DEM) is a numerical simulation method for dealing with discontinuous medium problems. And it is widely used in the field of bulk material processing. EDEM (enhanced distinct element method) software is a general CAE (computer aided engineering) analysis software based on the DEM, which is commonly used to simulate and analyze particle processing and operating system in industry and agricultural production. At present, its application in crop harvesting has not been reported, but it has been successfully applied in the field of agriculture, especially in the treatment of soil matrix. The discrete element simulation model of vegetable drawing process was established by using discrete element software EDEM, and the optimal drawing force and drawing effect were determined by studying the mechanism of pulling the vegetables. According to the simulation analysis, the relationship between the pulling force of vegetables and the displacement of vegetables and the simulation process of vegetable drawing were obtained. It was determined that the minimum drawing resistance was 26.87 N when adopting the optimum drawing distance of 20 mm. The maximum safe drawing load of vegetable rhizome was 37.5 N and the maximum safe compression load of vegetable stem was 84.36 N under the condition of safety factor of 1.1, using small universal testing machine. According to the upper and lower limits of the drawing force and the mathematical parameters of the drawing, the inclination angle of the planting trough, which met the requirement of planting 1-6 rows of vegetables, was determined to be 17.8°. And at this angle of inclination, the maximum thrust value of the stem of the vegetable was less than the maximum destructive force of the vegetable 84.36 N. The final working parameters were applied to the single-row prototype test, and the good harvesting effect was obtained, which verified the rationality of the key parameters of the vegetable harvester.