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Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Grain loss rate is one of the most important performance index of corn head in mechanized harvesting. Seed harvesting is the main development direction of mechanized corn harvesting. The characters of seed harvesting corn variaty increased the urgency to reduce grain loss on corn head. The paper was proposed to solve the problem of grain loss on corn head. Theoretical analysis was conducted to the snapping process. Corn ear was subjected to pull force by the snapping rolls and the pull force transferred by corn stalk. Corn kernels were divided into 2 types due to their force condition. A kernel at the bottom end of corn ear was subjected to reaction forces by stripper plates, corn cob and the adjacent kernels and shear force by the pedicel. Kernels out of contact with the stripper plates were subjected to reaction forces by the adjacent kernels, pull force and shear force by corn cob. As the impact force was related to the impact time according to the theorem of impulse, the paper analyzed collision model between corn ear and stripper plates in the snapping process. A mathematical model was obtained about the impact time and intrinsic parameters of the system. The impact time was dependent on system mass, stiffness coefficient and damping coefficient, which lays on the mechanical structure and materials of collision objects. So, the impact force would decrease as the impact time could be prolonged by reducing the stiffness coefficient and raising the damping coefficient. The quantity of shed kernels could be reduced consequently. The paper proposed a corn head with wheel type rigid-flexible coupling snapping device to reduce loss. The corn head consisted of the frame, gear-box, snapping rolls, gathering chain, wheel type rigid-flexible coupling snapping device, and chain wheels. The wheel type rigid-flexible coupling snapping device consisted of snapping wheel axle, spring seat axle, supporting axle, buffer spring, and snapping wheel frame. Force analysis was conducted on the snapping wheel. According to the force conditions and dimension boundary condition, the structure diameters of snapping wheel, snapping wheel frame, and buffer spring were confirmed. In order to obtain the optimal parameters with the minimum loss rate of wheel type rigid-flexible coupling snapping device, the optimization experiments were conducted of the factors at 3 different levels. In the optimization experiments, the snapping wheel radius was designed at 10, 15 and 20 mm respectively, the flexible body thickness was at 2, 4 and 6 mm respectively, the snapping rolls rotating speed at 700, 800 and 900 r/min respectively. The Response Surface Analysis method was used to design the experiments. The software Design-Expert 8.0.6.1 was used to analyze the data. Regression equation was induced according to the experiment and analysis above. The optimal combination of wheel type coupling snapping device was as follows: The snapping rolls rotating speed was 700 r/min, the snapping wheel radius was 15 mm, the flexible body thickness was 4 mm. Verification contrast test was conducted between corn head with wheel type rigid-flexible coupling snapping device and the one with snapping rolls and stripper plates on corns at different moisture contents. As the kernels moisture contents were 21.8%, 16.7% and 13.4%, the grain loss rate decreased 53.4%, 48.6% and 47.0% respectively. This study provides not only theoretical basis but also design reference for the improvement of corn harvester design. [ABSTRACT FROM AUTHOR]

Due to long stubble remained in farmland after harvesting as well as hardened and impervious soil in southern farmland of China, the tillage and land preparation parts of multifunctional rape-planting machine tend to wind grass and obstruct with mud, which impairs the working performance of ridging equipment and reduces the percentage of rapeseed seedling germination. In order to solve these problems, a rapeseed planting method is proposed, which combines the straw mulching cultivation with the direct seeding. The method is used to collect and cut the rice stubbles, and then the chopped rice stubbles are evenly covered on the inter-row spaces without involving the tillage apparatus. A multifunctional rape-planting device is mounted to a rice combine-harvester by replacing screening device, using the original harvester header to collect the rice stubbles and replacing the threshing cylinder to chop and scatter the rice stubbles. In this paper, an air-assisted chopping mechanism was designed, in which the moving knives and the transplanting blades were coaxially installed. The performance of the air-assisted chopping mechanism was evaluated by simulating the chopping operation of "stalk-standing" and "crop residue" in farmland through a bench test driven by an electric motor. A quadratic orthogonal rotating experiment was designed by Design-Expert software. Based on the variance analysis and regression fitting, a multiple regression equation was obtained, showing the effects of the rotating speed of feeding press rolls, the rotating speed of rotation shaft of moving knives and the gaps between moving knife and stationary knife on the qualified rate of chopped stalk length and the power attenuation. It was shown that the rotating speed of rotation shaft of moving knives had the most influential effect, followed by the gaps between moving knife and stationary knife, and the rotating speed of feeding press rolls had the least effect on the qualified rate of chopped stalk length and the power attenuation. The response surface method was applied to optimize the operation conditions. The optimum factors for "stalk-standing" and "crop residue" chopping operation were as follows: The rotating speeds of feeding press rolls were 399.2 and 401.64 r/min, the rotating speeds of rotation shaft of moving knives were 968.12 and 977.23 r/min, and the gaps between moving knife and stationary knife were 0.52 and 0.49 mm, respectively. Under the optimal condition, the corresponding qualified rates of chopped stalk length for "stalk-standing" and "crop residue" were 95.89% and 97.09%, as well as the power attenuations were 3.04 and 2.6 kW, respectively. The differences between the experimental and the software analytical value of the qualified rate of chopped stalk length for "stalk-standing" and "crop residue" were both 0.11% and those of power attenuation were 0.05 and 0.08 kW, respectively, which indicated that the software analytical value was in great agreement with the experiment value. Based on the theoretical analysis, the higher qualified rate of chopped stalk length could be achieved under the faster rotating speed of rotation shaft of moving knives and the smaller gaps between moving knife and stationary knife. Taking into consideration the existing form of rice straw in farmland, the rotating speed of feeding press roll was designed to be 401.64 r/min, the rotating speed of rotation shaft of moving knife 977.23 r/min, and the gap between moving knife and stationary knife 0.49 mm. It can provide technical support for the design of rapeseed planter with the combination of straw-mulching cultivation and direct seeding. [ABSTRACT FROM AUTHOR]

The stem tip of vegetable sweet potato is an excellent nutritious and healthy food, which is widely used in many countries. It’s estimated that the total value of Chinese vegetable sweet potato’s market is about tens of billions of yuan, which means it has a promising future. Due to the difficulties of the long harvest period, high harvest requirement, and low mechanized level, the high cost and low efficiency in harvest is prominent. As such, it decreases the motivation of the farmers deeply. Also, the market still has a strong need for the stem tip harvester urgently. In order to fill the blanket in the mechanized harvest on stem tips of vegetable sweet potatoes in China, and to solve the current problems, in this research, we designed a stem tip harvester for vegetable sweet potatoes in combination with agronomy, which was composed of the reeling, cutting, conveying and collecting devices. It could finish cutting, conveying and collecting the stem tips for vegetable sweet potatoes every single row in one operation. In this paper, we introduced the harvester’s working theory based on analyzing the whole machine’s mechanical structure. To improve the integrity rate of stem tip, to lower the missing rate in cutting, to lower the stubble height and to improve the harvester’s working quality, we did a test on the harvester’s working parameters, using Box-Benhnken's central combination test method based on the single factor test. Three-level quadratic regression orthogonal experimental design was done through the forward speed, the reel speed and the reciprocating cutter line speed. The model of response surface was established to research and analysis the machine’s working quality due to different factors. Finally, the optimization of machine operation parameters was realized. The results showed that the prominent order in the stem tips’integrity rates was the reel speed > the reciprocating cutter line speed > the forward speed. The prominent order in the stem tips’missing rate was the forward speed > the reciprocating cutter line speed > the reel speed. The prominent order in the stem tip’s stubble height was the reel speed > the forward speed > the reciprocating cutter line speed. In 2019, the test was done in three times to verify the model’s correction in Baiba test base, Nanjing Research Institute for Agricultural Mechanization. The field test results showed the optimal working parameters were the forward speed 0.38 m/s, the reel speed 26 r/min, and the reciprocating cutter line speed 0.60 m/s. The integrity rate of stem tips was 97.10%, the missing rate was 12.11%, and the stubble height was 62.09 mm. The error was in the range of 5% compared to the theoretical optimization. Compared with the single manual picking efficiency of 0.001 hm²/h, the operating efficiency of this machine can reach 0.1 hm²/h, The operation effect of the machine was obviously improved compared with that of manual operation, better to meet the requirements of the vegetable sweet potatoes’stem tips machinery harvesting. The test research supplies a strong support and theoretical basis to the mechanical development of the harvester for vegetable sweet potatoes’stem tips. [ABSTRACT FROM AUTHOR]