夹茎式番茄钵苗取苗机构设计与试验

为避免取苗机构在夹取钵苗过程中对钵体与根系造成损伤,该研究针对夹茎取苗方式,提出一种基于二阶椭圆齿轮行星轮系以及凸轮摆杆机构的夹茎式番茄钵苗取苗机构。依据二阶椭圆齿轮传动特性与机构工作原理,建立机构运动学理论模型,并对凸轮轮廓曲线进行设计,结合番茄钵苗取苗作业要求及机构特点,基于MATLAB软件开发机构分析软件对机构参数进行优化,并进一步分析优化后取苗轨迹与凸轮各工作段的对应位置关系,建立了夹茎式取苗机构虚拟样机模型,利用ADAMS软件对取苗机构运动过程进行仿真分析,验证机构参数优化结果及零部件结构设计的准确性与合理性。试制取苗机构物理样机开展高速摄影试验,通过对比分析实际工作轨迹与理论分析及仿真轨迹的一致性,验证了取苗机构设计的正确性。搭建自动取苗试验台进行取苗试验。试验结果表明,取苗机构工作性能可靠、稳定,取苗频率为80株/min时,取苗成功率为92%,投苗成功率为94.2%,伤苗率为2.9%。研究结果可为番茄钵苗全自动移栽机自动取苗机构的研发提供参考。

Design and experiment of seedling picking mechanism by stem clipping for tomato plug seedling

Technology of seedling transplanting is widely used in the tomato planting in Xinjiang, Western China. In recent years, the demanding for the automatically transplanting machine increases rapidly, with the continuous expansion of planting scale. Nevertheless, most transplanting machines used in Xinjiang are semi-automatic transplanters, which still need the manual operation to complete seedling picking and dropping. Thus, it is very imperative to develop the automatic transplanter for the plug seedlings of tomato. As one of the key components in an automatic transplanter, the seedling picking device can pick plug seedlings and then drop them automatically with a preset movement trajectory. Since the stems of tomato plug seedlings have good mechanical properties in a suitable period, in this study, a novel seedling picking device in a stem clipping type was designed for the tomato plug seedlings, using the special mechanism of second-order elliptical planetary gear train and cam swinging rod. An automatic seedling picking test-bed was built for the tomato seedling picking experiment, which was carried out in the Key Laboratory of Northwest Agricultural Equipment of Ministry of Agriculture and Rural Affairs, China. The picking mechanism in a stem clipping type showed a good effect on reducing the damage rate of plug seedling, while improving the efficiency of seedling picking. 1) The kinematic model of seedling picking mechanism was established by analyzing the transmission characteristics of second-order elliptic gear, meanwhile, the actual contour curve of cam was also explored. A specific optimization objective of mechanism parameters was proposed, according to the requirements of picking tomato seedling, and the structural characteristics of seedling picking mechanism. A human-computer interaction optimization software was established on the MATLAB software to optimize the structure parameters for the stem clipping type in a seedling picking device. 2) A dataset on the optimal combination of mechanism parameters was obtained by the human-computer interaction analysis, indicating to satisfy the requirements of oblique clamping and straight pulling operation, when the seedling picking mechanism working. The virtual prototype of seedling picking mechanism in a stem clipping type was designed on the SOLIDWPORKS software, and then the physical prototype of mechanism was developed, according to the optimized structural parameters. 3) The virtual simulation of device and high-speed photography experiment were carried out, in order to verify the accuracy of the optimized structural parameters. The results showed that the relative trajectories at the endpoint of seedling clip captured from a high-speed camera were basically consistent with the theoretical trajectories and virtual prototype simulation. According to the picking experiment of tomato plug seedling, the success rate of seedling picking reached 92%, when the seedling frequency was set as80 plants/min, while, the damage rate of seedling was only 2.9%, and the success rate of dropping seedlings attained to 94.2%. The test results showed that the seedling picking mechanism was stable and reliable when working, indicating that the mechanism can perfectly meet the agronomic requirements of mechanical seedlings picking for tomato plug seedlings. The findings can provide an important reference and technical support for the development of automatically picking mechanism in plug seedling.