胡萝卜缨果拉拽式分离损伤机理及实现机构设计方法研究

When working, the traditional trolley that separates the carrot tassel and theroots is the sine regular movement，leading to the problem of incomplete and poorconsistency separation of carrot. At the same time the rod and carrot collision,friction caused carrots injury.. In this project, we propose a non-circular gear-driven carrot system with anti-friction rods, and carry out theoretical modeling, parameter optimization and experimental study to achieve low injury, good consistency and thorough separation.Specific research content: The injury mechanism of Carrot 's tassel and fleshy root separation is explored; The injury model of the carrot - pulling process was established and tested; To reduce the injury of carrots as the goal,the friction reduction structure is designed and the parameters are optimized; The servo motor - driven carrot - pulling separation test bench was developed and the ideal kinematic characteristics of the drawbar were studied; The kinematic characteristics of the carrot rods driven by the non-circular gear are modeled, and parameter optimization and experimental study are carried out to realize the ideal kinematic characteristics.. In this project, the injury model and the carrot separation mechanism of the pull carrots were established, and provides technical support for the development of new carrot harvester. The general model for the design of high-order free-section curve non-circular gears for specific non-uniform speed transmission is of general significance in the field of mechanics.

传统胡萝卜拉拽式缨果分离机构工作时拉拽杆做正弦规律运动，存在胡萝卜缨果分离不彻底和一致性差的问题；同时拉拽杆与胡萝卜碰撞、摩擦导致胡萝卜损伤大。本项目拟提出非圆齿轮驱动的带减摩拉拽杆的胡萝卜缨果分离机构，并进行理论建模、参数优化和试验研究，以达到损伤低、一致性好、分离彻底的效果。具体研究内容：探索胡萝卜缨果拉拽式分离损伤机理，建立胡萝卜拉拽式缨果分离过程的损伤模型并试验；以减少胡萝卜损伤为目标的减摩拉拽杆结构创新和参数优化；研制伺服电机驱动的拉拽式胡萝卜缨果分离试验台并研究拉拽杆理想运动学特性；建立非圆齿轮驱动的胡萝卜拉拽杆运动学特性分析模型，进行参数优化和试验研究，以实现理想运动学特性。本项目所建立的拉拽式胡萝卜缨果分离损伤模型及研制的胡萝卜缨果分离机构，为开发新型胡萝卜收获机提供技术支撑；建立的针对特定非匀速传动要求的高阶自由节曲线非圆齿轮优化设计通用模型在机构学领域具有普遍意义。

胡萝卜是一种具有较高营养价值的伞形科植物，原产于中亚细亚一带，我国是世界上最大的胡萝卜生产国之一，目前，我国针对缨果分离阶段的研究相对较少。本研究的核心内容是胡萝卜缨果拉拽式分离的损伤机理研究与缨果分离装置的研制，从测量并统计胡萝卜的外观尺寸及力学材料特性开始，完成了基于Abaqus/Explicit建立胡萝卜与拉拽杆的碰撞模型，并通过摆锤试验验证有限元模型的可靠性；进行胡萝卜与拉拽杆碰撞损伤因素分析，并提出减损措施；建立减损措施后的仿真模型，求解胡萝卜的损伤临界相对速度；通过建立缨果拉拽式分离机构的运动学和动力学模型，导出拉拽杆运动与胡萝卜损伤的关系，计算拉拽杆的临界转速；根据拉拽杆非匀速运动特性设计设计非圆齿轮传动装置，最后研制出样机，通过试验完成对样机性能进行检验。完成的主要工作如下：.1）对胡萝卜的外形尺寸进行测量及统计，试验获得了胡萝卜果心层和果肉层的弹塑性参数，粘弹性参数。.2）通过高速摄像观察胡萝卜缨果拉拽式分离下，胡萝卜与拉拽杆主要相互作用主要为碰撞。基于Abaqus/Explicit建立胡萝卜与拉拽杆的碰撞模型，预测胡萝卜碰撞损伤的临界冲击力为45.2 N，并设计摆锤冲击装置在相同条件下试验，验证仿真结果与试验结果误差为4.87%；提出减损措施，求解拉拽杆在减损前和减损后胡萝卜的损伤临界速度分别为1.3 m/s和1.58 m/s。.3）建立缨果拉拽式分离机构的运动学模型，计算圆盘临界转速为183 r/min；建立缨果拉拽式分离机构的动力学模型，计算所需最小的输入扭矩。.4）设计缨果拉拽式分离机构的非圆齿轮传动装置，完成样机研制并试验，胡萝卜缨果分离成功率为90%。