扦插钵苗顶夹式取苗装置优化设计与试验

Optimization Design and Experiment on Top-clamping Seedling Extraction Mechanism for Cutting Plug Seedling

摘要:

针对扦插钵苗因根系固结力不足及冠层扩展性显著引发的基质破碎率高、取苗成功率低等机械化移栽难题,提出一种基于顶夹式取苗方案的低损伤高效取苗装置。通过结合非圆齿轮行星轮系传动特性与“平夹直拔”的轨迹原理构建夹取机构运动学模型,经参数优化获得关键结构参数:行星架长度为100mm、取苗臂长度为130mm、锁止弧基准半径为35mm、接触角为44.43°,使传动比波动范围降低59.31%。在此基础上,基于两杆转角映射关系推导非圆齿轮节曲线。以红叶石楠扦插钵苗为试验对象,结合离散元仿真与试验验证,确定顶杆直径6mm、行程6mm、速度28mm/s、取苗效率60株/min为最优作业参数组合,试验结果表明,在此作业条件下,取投苗成功率为94.33%,基质破碎率小于等于3%,茎秆损伤率小于等于1.67%,且无明显伤苗现象。该装置通过楔形块推动顶杆以降低基质-穴盘界面粘附强度,结合“蚕豆”形取苗轨迹的夹取机构实现低损高效取苗,满足扦插苗自动化移栽的要求。

Abstract:

Aiming to address mechanical transplantation challenges of vegetative cutting plug seedlings caused by insufficient root anchorage strength and significant canopy expansion, leading to high substrate fragmentation rates and low seedling extraction success, a low-damage high-efficiency seedling extractor was proposed based on a top-clamping mechanism. By establishing a kinematic model of the clamping mechanism based on non-circular gear planetary transmission characteristics and a “ linear clamping- vertical extraction” trajectory principle, key structural parameters were optimized through parameter optimization to minimize transmission ratio fluctuations: planetary carrier length (100 mm), extraction arm length (130 mm), locking arc base radius (35 mm), and contact angle (44. 43°), achieving a 59. 31% reduction in transmission ratio fluctuation. The non-circular gear pitch curve was derived based on the angular mapping relationship of a two-bar linkage mechanism. Combining discrete element method (EDEM) simulations with experimental validation using Photinia × fraseri cutting plug seedlings, optimal operational parameters were determined: ejector diameter (6 mm), stroke (6 mm), speed (28 mm/ s). At a seedling extraction rate of 60 seedlings/ min, the extraction and delivery success rate reached 94. 33% , substrate fragmentation rate remained below 3% , and stem damage rate was under 1. 67% , with no observable seedling injury. The device employed a wedge-shaped actuator to reduce adhesion between the substrate and seedling trays, combined with a kidney-shaped clamping trajectory for low- damage and high-efficiency seedling extraction, meeting the requirements for automated transplantation of cutting seedlings.