Structural optimization of duckbilled transplanter based on dynamic model of pot seedling movement

Abstract: In the working process of duckbilled transplanter, leakage and seedling lodging happen frequently when the transplanting speed is too fast. Aiming at analyzing the reason of that and providing a solution, transparent PMMA and high speed video camera were used to record the motion process of pot seedling in duckbilled planter in this study. Based on the results of the experiment, the interaction characteristics between the pot seedling and the duckbilled planter were studied and analyzed. Planting mechanism of pot seedling under high speed operation was studied to demonstrate the fundamental cause of the increase of seedling lodging rate and leakage rate. This study provided a theoretical basis for the optimal design of speed and structure of duckbilled planter. First of all, the rotation planting mechanism of planetary gear train was developed in this paper. There were four duckbilled planters made of pure plexiglass on the mechanism. After that, a high speed camera was used to analyze the movement of the pot seedling falling from the seedling cup to the bottom of the planter. According to the results of the experiment, the moving process of the pot seedling in the duckbill planter was divided into six stages, which were 1) free dropping stage, 2) colliding with the planter wall, 3) slanting motion in the planter, 4) collision with the duckbill wall, 5) plan motion in duckbill, and 6) sliding along with the duckbill planter wall. The dynamic model of each movement stage was established. The equation of motion force between the pot seedling and the duckbill planter during the falling stage was obtained. Pepper seedlings at age of 40 d were used to conduct the experiment. The seedlings were cultivated in the growth medium made of peat, vermiculite, and perlite with ratio of 3∶1∶2. The moisture content of the medium was 55%. The optimum initial position and structural parameters of the planter were obtained by optimizing the moving time of the seedling and optimizing the kinetic model of the seedling movement. By analyzing the result, a series of optimal parameters were obtained. The optimal initial position of the pot seedling was 40 and 350 mm for the x-and y-axis, respectively. The optimal angle between the vertical surface and the wall of the seedling cup on the duckbill planter was 40°. The optimal tilting angle of the duckbill on the planter was 82°. Maximum rotation speed of planting mechanism was under 80 r/min. The optimal initial phase angle of the planter was 25°. The motion time of pot seedling in the improved planter was analyzed by using a high speed camera. From the high speed camera test, it was found that when the rotation speed of planting mechanism was 80 r/min, the pot seedling had already left the planter before the planter moved to the lowest point. The time of the seedling falling was less than the time from the seedling beginning falling to the planting mechanism moving to the lowest point. It showed that the optimized planter was feasible to complete the seedling transplanting successfully. The improvement of the planting mechanism design was verified. A high speed post-processing software, PCC, was used to obtain the time of seedling beginning to fall and the time of leaving the planter. Under the optimum initial seedling drop position, the optimum initial phase angle of the planter and the optimum structural parameters of the planter, the drop time of the seedling was obtained. It was concluded that the time from the beginning falling to leaving the planter was basically consistent with the theoretical value. The seedling fell to the bottom of the planter before the planter moved to the planting position. The correctness of the theoretical model and the rationality of parameter optimization were verified. The research can provide reference for structure design and optimization of the high speed duckbilled transplanter.