| Compared with the traditional transplanting method,rice pot seedling transplanting has the advantages of no root injury,no delayed seedling stage,yield increased easily and so on.It is also an important means to solve the planting requirements of 1-2 seedlings per hole of super rice.At present,rice pot seedling transplanting mainly adopts the transplanting method of clamping seedlings.According to the series of action characteristics of seedling clamping,seedling extraction,seedling carrying and seedling planting in transplanting,the transplanting mechanism should generally be able to realize the 8 shaped transplanting operation trajectory.Some of the existing transplanting mechanisms of rice pot seedlings have small ring buckle,which affects the success rate of seedling picking;some of transplanting mechanisms are easy to cause seedling inversion when the position of planting point is too high;some transplanting mechanisms with the small angle of seedling push is not conducive to seedling establishment.The reason is that the transplanting mechanism design process is mainly oriented to the study of trajectory shape,not a reasonable consideration with transplanting attitude and trajectory shape;or the parameter design of the transplanting mechanism is only based on the few poses(three or four key posture).It is impossible to give full play to the ability of the existing mechanism configuration in transplanting trajectory and attitude.In this paper,through the comparative experiments of the existing two sets of transplanting mechanisms,several key position and attitude points to meet the requirements of transplanting agronomics are analyzed and obtained,and a design method of non-circular gear planet gear train transplanting mechanism based on the kinematic mapping approximate synthesis of eight positions is proposed.The main research contents are as follows1)The tensile strength test of rice seedlings and the comparative test of two sets of rice pot seedlings transplanting mechanism were carried out,and the seedling age,clamping Angle and eight key positions of seedlings that could maintain good tensile strength were analyzed and obtained.2)Combined with the kinematic mapping theory,three groups of RR two-bar groups are obtained.two groups of suitable two-bar groups are selected to obtain a set of four-bar mechanisms and a closed-loop 8-shaped trajectory to meet the requirements according to the limitation of the working range of the transplanting mechanism.Some type points are selected from the trajectory to fit the new closed trajectories,and the transmission ratio is assigned.A pair of non-circular gear pitch curves are generated,which can meet the requirements of 8-shaped trajectory transplanting.3)Some key open-loop trajectory segments are intercepted from the trajectory,some type points selected to fit a new closed trajectory,and the transmission ratio is assigned to generate the non-circular gear pitch curve before optimization.The objective function is established based on genetic algorithm and a pair of non-circular gear pitch curves with good concavity and convexity are obtained by local optimization.4)The three-dimensional model establishment,the virtual prototype simulation and the idling test of the transplanting mechanism are completed,and the consistency between the theoretical calculation and the actual design is verified.The seedling-picking test of the new seven-gear rice-pot seedling transplanting mechanism was carried out.The reason of the seedling leakage is analyzed and the clips structure is improved.The success rate of the seedling picking was 91.98%,and the field transplanting experiment was carried out. |
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