基于FEM-SPH模型的番茄钵苗非圆行星轮系取苗机构设计与试验

Design and Experiment of Non-circular Planetary Gear Transplanting Mechanism for Tomato Pot Seedling Based on FEM-SPH Model

摘要:

针对配置探出式取钵执行装置的大田番茄钵苗取苗机构存在未能有效控制根系损伤和作业效率低的问题, 本文采用数值模拟与仿真分析方法,围绕取钵过程中的钵体损伤特性展开研究。 在此基础上,设计一种基于非圆齿轮行星轮系的番茄钵苗取苗机构。 首先建立番茄钵苗及探出式取钵执行装置 FEM-SPH 耦合模型, 结合 ANSYS / LS-DYNA 软件取钵互作过程数值模拟仿真结果,从取苗刀片接触力、钵苗应力变化分析钵体损伤规律与影响因素;提出配置探出式取钵执行装置的双臂式番茄钵苗非圆齿轮行星系取苗机构,开展基于 Catmull-Rom 样条曲线拟合方法的取苗机构反求设计研究,并通过所开发的 Matlab 计算机辅助设计软件完成机构参数优化。 新轨迹取苗过程数值模拟仿真结果表明,取苗刀片扎入瞬间等效应力较原轨迹减少 4. 4% ,应力变化更平缓,初步验证机构可降低基质破碎及根系损伤风险。 开展取苗机构物理样机台架测试与性能试验,力学传感器测试结果表明, 刀片与土钵最大接触力与数值模拟平均相对误差为 3. 76% ,4 种转速下成功率均在 94% 以上,验证了双臂式番茄钵苗非圆轮系取苗机构数值模拟模型的正确性及机构设计的可行性。

Abstract:

The in-field tomato seedling extraction mechanism equipped with a telescopic pot retrieval device suffers from issues of ineffective root damage control and low operational efficiency. Employing numerical simulation and computational analysis methods to investigate the pot damage characteristics during the extraction process, a novel tomato seedling extraction mechanism was designed, utilizing a planetary gear system with non-circular gears. Firstly, the FEM-SPH coupled model of tomato pot seedlings and the extensible type seedling pot picking device were established. Combined with the numerical simulation results of the pot-picking interaction process by using ANSYS / LS-DYNA software, the laws and influencing factors of pot damage were analyzed from the aspects of the contact force of the seedling picking blade and the stress change of the pot seedling. A double-arm non-circular gear planetary system seedling picking mechanism for tomato pot seedlings equipped with the extensible type seedling pot picking device was proposed. The reverse design research of the seedling picking mechanism based on the Catmull-Rom spline curve fitting method was carried out. The optimization of mechanism parameters was completed by using the self-developed Matlab computer-aided design software. The numerical simulation results of the seedling picking process with the trajectory showed that the equivalent stress at the moment the seedling picking blade penetrates was decreased by 4. 4% compared with the original trajectory, and the stress change was smoother, which initially verified that the mechanism can reduce the risk of substrate fragmentation and root damage. Bench tests and performance tests of the physical prototype of the seedling picking mechanism were carried out. The test results of the force sensor showed that the average relative error between the maximum contact force between the blade and the soil pot and the numerical simulation was 3. 76% , and the success rate was above 94% at four rotational speeds, which verified the correctness of the numerical simulation model and the feasibility of the mechanism design of the double-arm non-circular gear train seedling picking mechanism for tomato pot seedlings.