Design And Testing Of Transplanting Mechanism For Regeneration Rice Based On Spatial Positions And Postures

Improving the multiple cropping index of rice field is an important way to increase rice yield and income effectively.The planting and harvesting mode of ratooning rice named"one harvest and two harvests"different from the double cropping rice mode of two harvests a year using light energy can effectively reduce farmers’investment in means of production,which is a resource-saving mode that saves labor,fertilizer,high yield and high efficiency.In order to solve the problem that the 300mm row spacing commonly used in the existing rice transplanters that does not match with the width and gauge of the track of rice harvesters（rolling rice piles）and does not conducive to mechanical harvesting,domestic agricultural experts put forward a mode of combining ratooning rice planting with wide and narrow row（high light efficiency）planting by reasonable increasing the row spacing of the crawler for effectively reducing the rolling of the harvester..In recent years,different types of wide and narrow row transplanting machines have been formed through the wide and narrow row arrangement and inclined arrangement of the traditional transplanting mechanism of rice transplanter.The research and development of space trajectory transplanting mechanism（plane gear swing arm type and space gear wheel type）has been made great progress.However,there are still the following shortcomings from the quality of machine operation and the matching with existing equipment:1)It is not matched with the traditional seedling-raising assembly line;2)serious root injured caused by oblique seedling taking;3)Insufficient lateral offset for ratooning rice planting.Therefore,the wide and narrow row transplanting mechanism is studied matched with the seedling-raising equipment which can realize the spatial straight seedling taking action,the large lateral offset and the small hole operation trajectory focusing on the demand of mechanized planting of ratooning rice in China and aiming at the limitations of the design and application of wide and narrow row transplanting mechanism.The specific research contents are as follows:1)The forming mechanism of the waist-shaped trajectory of the wide and narrow row gear train transplanting mechanism was studied on the premise of not changing the traditional seedling gate according to the line spacing requirement of mechanized planting of ratooning rice in wide and narrow rows,and the ideal operation trajectory which can simultaneously realize the straight seedling picking,large deflection moment and small hole opening was put forward.（the total offset of seedling picking and pushing point:z₅-z₁=65mm,Total offset of seedling section:0≤z₃-z₁≤15mm;Lateral cavity:10mm≤z₆-z₄≤30mm）.2)The simplified model of spatial open-chain 2R mechanism is established by reducing the gear pairs of the wide and narrow row gear train transplanting mechanism.The spatial constraint equations including the geometric characteristics of the key three-position posture of the transplanting trajectory are established by analyzing the ideal transplanting trajectory and the posture of the mechanism.,Two groups of real number solutions of basic parameters of spatial 2R mechanism are obtained by homotopy algorithm.The real number solution satisfying the conditions is obtained by screening according to the conditions such as reasonable rod length parameters of the transplanting mechanism.3)The space planetary gear train of plane non-circular gear and helical gear combination transmission is proposed as a wide and narrow row transplanting mechanism configuration based on the comprehensive analysis of space planetary gear train.The interpolation optimization of relative angular displacement near the key three position points was carried out to obtain better trajectory of the straight seedling segment and lateral cavitation.The pitch curve of non-circular gear was optimized by genetic algorithm and the pitch curve with better roundness was selected based on the concavity evaluation index of non-circular gear.4)The model of the straight transplanting arm and the whole mechanism were established solving the problems of interference between the seedling needle and the seedling door and the oblique seedling taking.Through the simulation analysis of the virtual prototype,it is found that the information parameters of the virtual prototype at the key three-position pose points within ideal trajectory planning range mentioned above-（the offsetΔS₁ of the seedling pushing point is 65.59mm,the offsetΔS₂ of the straight seedling picking section is 13.34mm,and the lateral holeΔS₃ is 23.69mm）,which proves the correctness of the motion synthesis method in this paper.5)The transplanting mechanism and the seedling taking test bed were set up,and the seedling taking test of the physical prototype were carried out.The experimental data were obtained that the success rate of seedling taking of transplanting mechanism was 92.31%,91.32%and 90.76%at the transplanting speeds of 90,120 and 180 plants/min,respectively.Moreover,the seedling taking blocks were complete and uniform,and the seedling pushing points were concentrated,which can meet the requirements of ratooning rice.The influencing factors were analyzed in view of the shortcomings of seedling taking experiment.