Design and Optimization of Planting Process Parameters for 2ZYX-2 Type Green Onion Ditching and Transplanting Machine

Considering the current low level of mechanization for domestic green onion planting and the high labor intensity of artificial planting,a 2ZYX-2 green onion ditching and transplanting machine,which can complete ditching,ridging,transplanting,repression,soil covering and other operations,is designed in this study.The Central Composite test design method was carried out with the speed of the transplanting machine,the depth of the opener and the horizontal position of the opener as the experimental factors and with the qualification ratio of perpendicularity,the variation coefficient of the plant spacing and the qualification ratio of the planting depth as the test index.Through the analysis of the model interaction and response surface,the change laws that the influence the machine’s forward speed,the depth of the opener and the horizontal position of the opener were studied.The regression model was optimized by Design-Expert 8.0.6 software,and the accuracy of the predicted results was verified by experiments.The optimal working parameters showed that the forward speed of the machine was 0.06 m/s,the depth of the opener was 102 mm,and the horizontal position of the opener was 29 mm.Under conditions of optimal working parameters,the qualification rate of the verticality was 86.83%,the coefficient of variation for the plant spacing was 2.77,and the pass rate of planting depth was 88.26%.The research related to the thesis can provide a reference for the mechanized planting of green onion,which is of great significance to the cost-effectiveness of the green onion industry.

Geometrical design of variable ratio tooth profile based on Boolean subtraction operation and a novel modification method

Variable transmission ratio racks show great potential in rice transplanters as a key component of variable transmission ratio steering to balance steering portability and sensitivity.The objective of this study was to develop a novel geometrical design method to achieve quick,high-quality modeling of the free curvilinear tooth profile of a variable transmission ratio rack.First,a discrete envelope motion 3D model was established between the pinion-sector and the variable transmission ratio rack blank based on the mapping relationship between the rotation angle of the pinion-sector and the displacement of the rack,according to the variable transmission ratio function.Based on the loop Boolean subtraction operation,which removed the pinion-sector from the rack blank during all moments of the discrete motion process,the final complex changing tooth shape of the variable transmission ratio rack was enveloped.Then,since Boolean cutting residues made the variable ratio tooth surface fluctuant and eventually affected the precision of the model,this study proposed a modification method for establishing a smooth and continuous tooth profile.First,a novel fitting algorithm used approximate variable ratio tooth profile points extracted from the Boolean cutting marks and generated a series of variable ratio tooth profiles by utilizing B-spline with different orders.Next,based on a transmission stability simulation,the variable ratio tooth profile with optimal dynamic performance was selected as the final design.Finally,tests contrasting the transmission stability of the machining samples of the initial variable ratio tooth profile and the final variable ratio tooth profile were conducted.The results indicated that the final variable ratio tooth profile is more effective than the initial variable ratio tooth profile.Therefore,the proposed variable ratio tooth profile modeling and modification method for eliminating Boolean cutting residues and improving surface accuracy is proved to be feasible.