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Vegetable pot seedling transplantation has many advantages, such as high survival rate, promoting crop early maturity and improving land use rate. Mechanized transplanting of vegetable can be divided into semi-automatic transplanting and fully-automatic transplanting. Semi-automatic transplanting is mainly carried out by feeding the seedlings into the seedling transplanter manually, which has low efficiency and high labor intensity, and it is not conducive to field operations. At present, the automatic transplanting machine mainly adopts multiple mechanisms to complete a series of actions such as picking up seedling, conveying and planting, but it has the disadvantages of complex structure, high cost and low efficiency. In order to simplify the structure, the way to complete the transplanting operation with a single mechanism is proposed. However, due to the complicated working trajectory of transplanting vegetable seedling and much posture requirements, the transmission ratio of the mechanism is required to be changed greatly, which resulting in the irregular shape of the non-circular gear section of the single planetary gear is not conducive to processing and affects the transmission performance of the gear. A double-planetary non-circular gears linkage of vegetable pot seedling transplanting mechanism is proposed to solve the problem mentioned above in this paper. The transmission part of transplanting mechanism is composed of planetary gear train mechanism and crank rocker mechanism, The main planetary frame rotates at a uniform speed, through the transmission of internal gears and connecting rods, the unequal transmission of non-circular gear system and the periodic variable-speed swing of crank-rocker mechanism are superimposed, which makes the sub-planetary frame swing with respect to the main planetary frame and the transplanting arm rotate with respect to the sub-planetary frame, thus the transmission ratio needed to realize the complex transplanting trajectory and posture is obtained. Non-uniform B-spline curve is applied to fit the pitch curve of non-circular gear to obtain closed, smooth and continuous pitch curves, and the mathematical model of gear train is established based on coordinate transformation theory. Based on the development platform of Matlab, an optimization program is compiled to analyze the effect of transmission case noncircular gear pitch curve and crank rocker mechanism on the shape of trajectory. Further, the effects of the structure and position parameters of the gears and transplanting arm on the target parameters of the transplanting trajectory are analyzed. According to the requirements of 220 mm planting spacing, 120 mm seedling height and 40 mm deep pot for celery transplantation, a set of sharp beak trajectory that satisfies the requirements of the operation posture of picking up seedling and planting is optimized. The optimizing values are that the length of the picking up seedling trajectory is 33 mm, the distance from the lowest point of the trajectory to the lowest point of the planet carrier is 55 mm, the angle of picking up seedlings is 23°, the angle of change in the process of picking up seedlings is 16°, the angle of planting seedlings is 65°, the whole height of the trajectory is 355 mm, and the height of the buckle of the moving trajectory is 125 mm. A three-dimensional model of the mechanism is built and a virtual simulation is performed based on the optimization result. The results show that the simulated trajectory and velocity of the transplanting mechanism are basically consistent with the theoretical results. The trajectory and postures of the transplanting arm are analyzed by a test bench, industrial camera and image processing software. The results show that the trajectory of seedling-taking and seedling-pushing sections coincides with the simulation trajectory basically and the theoretical data, and the error is within 2 mm, which can meet the requirements of transplanting operation, the transplanting mechanism designed is reasonable and feasible. [ABSTRACT FROM AUTHOR]