二次探出护钵式水稻钵苗移栽机构设计与试验

Design and Experiment of the Secondary Extension Pot-protecting Rice Pot Seedling Transplanting Mechanism

摘要:

为提升取栽一体式钵苗移栽机构的定植立苗效果,本文提出了一种二次探出护钵式移栽机构,通过对取栽一体式移栽臂进行功能解耦设计,借助推秧杆的两次递进式探出与夹爪的协同作业,依次实现钵苗的夹取、护钵与定植。该机构以平面凸轮和端面凸轮为核心驱动单元:平面凸轮驱动推秧杆两次递进式探出,依次完成护苗与植苗动作;端面凸轮控制夹爪开合,实现钵苗的夹取与释放。为达成凸轮机构低冲击、低磨损的设计目标,结合移栽运动技术要求与移栽臂结构参数,建立了凸轮机构运动学模型,基于曲线包络理论完成了凸轮轮廓设计。针对平面 凸轮机构,通过构建弹性动力学方程并制定接触力学优化策略,将凸轮与拨叉的接触形式优化为面接触,有效降低 了运动冲击;针对端面凸轮机构,引入了基于曲率约束的轮廓优化函数,优化了其压力角峰值特性。通过虚拟样机运动学仿真与物理样机田间试验对设计方案进行双重验证,结果表明:该移栽臂可显著降低钵苗栽插直立度对行星轮系转速的敏感性,在250 株/ (min · 行)作业工况下,钵苗直立度合格率达87. 50% ,较原移栽臂机构实现显著提升,适用于高速高质钵苗移栽作业场景。

Abstract:

Aiming to improve the seedling planting and establishment performance of the integrated seedling taking and planting pot seedling transplanting mechanism, a secondary extension pot-protecting transplanting mechanism was proposed. Through the functional decoupling design of the integrated seedling taking and planting arm, and with the cooperative operation of the two progressive extensions of the seedling pushing rod and the clamping jaws, the mechanism sequentially achieved pot seedling clamping, pot protection, and planting. The mechanism adopted planar cam and end cam as the core driving units: the planar cam drove the seedling pushing rod to perform two progressive extensions, sequentially completing seedling protection and planting actions; the end cam controlled the opening and closing of the clamping jaws to realize the clamping and releasing of pot seedlings. To achieve the design goals of low impact and low wear for the cam mechanism, combined with the technical requirements of transplanting movement and the structural parameters of the transplanting arm, a kinematic model of the cam mechanism was established, and the cam profile design was completed based on the curve envelope theory. For the planar cam mechanism, by constructing an elastodynamic equation and formulating a contact mechanics optimization strategy, the contact form between the cam and the fork was optimized into surface contact, which effectively reduced kinematic impact. For the end cam mechanism, a profile optimization function based on curvature constraint was introduced to optimize its peak pressure angle characteristics. The design scheme was double-verified through virtual prototype kinematic simulation and physical prototype field tests. The results showed that the transplanting arm can significantly reduce the sensitivity of pot seedling planting uprightness to the rotational speed of the planetary gear train. At a working speed of 250 plants/ (min · row), the qualified rate of uprightness reached 87. 50% , which was significantly higher than that of the original mechanism, making it suitable for high-speed and high- quality pot seedling transplanting scenarios.