基于钵苗运动动力学模型的鸭嘴式移栽机结构优化

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

为了探究鸭嘴式移栽机因栽植速度提升,导致钵苗倒伏率和漏栽率升高的根本原因,该文试制了纯透明有机玻璃质的鸭嘴式栽植器,并采用高速摄像对钵苗从导苗筒下落至栽植器底部的运动过程进行了试验研究。根据研究结果将钵苗在鸭嘴栽植器内的运动过程分为6个运动阶段,并建立了各运动阶段的动力学模型,得到了钵苗下落过程中与鸭嘴栽植器间的运动受力方程。选取苗龄为40 d,基质成分为草炭:蛭石:珍珠岩=3∶1∶2,钵苗土钵含水率为55%的辣椒钵苗为研究分析及试验对象,以钵苗栽植运动时间为优化目标,对钵苗运动过程动力学模型进行优化,得出了栽植器最佳初始位置及结构参数为:钵苗下落初始位置为(40 mm,350 mm),鸭嘴栽植器上苗杯壁面与竖直面间的夹角为40°,栽植器鸭嘴部分倾角为82°;栽植机构最高转速不超过80 r/min,栽植器初始相位角为25°。通过高速摄像试验对钵苗在改进后栽植器中的运动时间进行了分析,得出钵苗从开始下落至离开栽植器的时间与理论时间基本吻合,且在栽植器运动至栽植位置前钵苗已落至栽植器底部,验证了理论模型的正确性以及参数优化的合理性。该研究可为鸭嘴式移栽机高速栽植转速和结构设计提供参考。

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.