成排夹茎式大葱取苗机构优化设计与试验

Optimization Design and Experiment of Row Stem Clamped Scallion Seedling Harvesting Mechanism

摘要:

针对目前全自动大葱移栽机中投苗装置与接苗装置结构较复杂,取投苗效率不足的问题,本文开展一种基于非圆齿轮行星轮系成排夹茎双臂式大葱取苗机构研究。基于大葱夹茎式取送苗运动要求确定一种“8”字形取投苗轨迹与关键位姿,建立关键位姿和轨迹与机构参数的求解模型,求解获得机构运动学较优解,构建机构中非圆齿轮拓扑优化设计和取苗臂配重块模型,通过动力学分析软件进行机构动力学优化,得到拓扑优化后取苗臂配重块的质量和质心向径分别为439.8 g和20.35 mm,最后制作了大葱取苗机构样机并进行取苗试验与动力学性能对比试验。试验表明:在转速20 r/min时(取苗效率400株/min)葱苗的取苗成功率为87%;转速15 r/min下(取苗效率300株/min)葱苗的取苗成功率可达91%,表明机构具有高效取投苗性能。动力学优化后大葱取苗机构左、右侧转速幅值分别下降了17.29%、24.38%,方差分别减少了55.31%、60.70%;转速差幅值下降了42.63%,方差下降了34.91%,有效改善了机构动力学性能。

Abstract:

Regarding the current issues of complex structures and low efficiency in seedling feeding and receiving devices of fully automatic scallion transplanters, the research and design of an integrated seedling picking and feeding mechanism for scallions was presented based on a non-circular gear planetary gear system, featuring a row of clamped stems and dual arm structure. Based on the kinematic requirements for gripping-stem scallion seedling pickup and delivery, a figure-eight pickup-placement trajectory with key pose parameters was defined, solving models for mechanism parameters were established based on trajectory and pose constraints, and a near-optimal kinematic solution was obtained. Under the dynamic simulation and analysis based on Adams software, a topology optimization design of non-circular gears and a model of seedling arm counterweight were constructed. The mass and centroid radius of the non-circular gears and seedling arm counterweight after topology optimization were 439.8 g and 20.35 mm, respectively. The seedling picking mechanism of scallion was tested and compared with the dynamic performance optimization. The tests indicated that at 20 r/min (400 seedlings/min), the scallion seedling pickup success rate reached 87%, while at 15 r/min (300 seedlings/min), it achieved 91%, indicating that the mechanism had high performance in seedling retrieval. The left and right rotation speed amplitudes of the onion seedling picking mechanism were decreased by 17.29% and 24.38%, respectively compared with that before optimization. The variance of the left and right rotation speeds of the scallion seedling picking mechanism was decreased by 55.31% and 60.70%, respectively compared with that before optimization. The amplitude of the speed difference was decreased by 42.63% compared with that before optimization, and the variance of the speed difference was decreased by 34.91% compared with that before optimization, which verified the performance of the mechanism prototype.