蔬菜嫁接机器人柔性夹持搬运机构设计与试验

Design and Experiment on Flexible Clamping and Conveying Mechanism of Vegetable Grafting Robot

针对现有蔬菜嫁接机器人单手爪夹持搬运机构作业时需要在上苗、切削和对接工位往复旋转作业,限制了机器嫁接生产效率,存在夹持伤苗、操作人员上苗等待时间过长、易疲劳等问题,设计了一种四手爪柔性夹持搬运机构,能够实现上苗、切削和对接工位同步作业,以及秧苗柔性夹持与快速搬运,有助于提高机器嫁接效率。提出了基于缓冲材料的柔性夹持手爪和夹持力调节方法,分析了不同厚度EVA缓冲材料的压缩力学特性,得到缓冲垫完全闭合夹持条件下对不同秧苗的夹持力。利用ADAMS软件建立夹持搬运机构动力学仿真模型,分析了秧苗不同夹持力与旋转位移的变化规律,得出当夹持力小于0.4 N时秧苗脱离了夹持手的束缚,夹持力大于3.5 N时秧苗夹持与旋转作业稳定。机构性能试验结果表明:选取白籽南瓜苗和黄瓜苗为测试对象,柔性夹持手爪平均夹苗成功率为98.5%,比弧形夹持手提高4.5个百分点,伤苗率降低3.5个百分点,柔性夹苗效果显著;该机构嫁接平均速度为1052株/h,是同类型单手爪嫁接机作业效率的1.72倍,嫁接成功率为96.67%,大幅提高了嫁接机器人生产效率,能够满足工厂化嫁接育苗生产需求。本文研究结果可为高速嫁接机器人的夹持搬运机构设计和优化提供技术参考。

The disadvantages of artificial grafting are low efficiency and nonstandard quality of grafted seedlings.Therefore,this method cannot meet the needs of mass production of factory seedlings.Mechanical grafting can improve the quality of grafted seedlings and promote the standardization of grafting seedlings.At present,most of the grafting machines adopt the artificial method to carry on the seedling,and the single hand grafting limits the improvement of the production efficiency.Through the development of automatic seedling device to replace artificial seedling,the device has high requirements for seedling standardization,the success rate of seedling is only about 80%,and it cannot be used in actual production.Through the study of multi claw synchronous grafting process flow and reasonable optimization of grafting mechanism layout,grafting efficiency can be improved steadily.In the process of mechanical grafting,the clamping and conveying mechanism is the key part of seedling transportation,which is used to grasp and transport seedlings from the seedling loading station to the cutting and docking station.In view of the existing single gripper clamping and handling mechanism,it needs to rotate back and forth at the seedling loading,cutting and docking positions during operation,which limits the grafting production efficiency of the machine,and there are some problems such as clamping injured seedlings,too long waiting time for operators to load seedlings,and easy to fatigue.A four gripper flexible clamping and conveying mechanism was designed.This mechanism can realize synchronous operation of seedling loading,cutting and docking,and realize flexible clamping and rapid transportation of seedlings.It was helpful to improve the grafting efficiency of the machine.The transfer mechanism can complete one grafting seedling every 90°rotation.At the same time,the flexible gripper based on buffer material and the adjustment method of clamping force were also proposed.The compression mechanical properties of EVA cushion material with different thickness were analyzed,and the clamping force of EVA cushion on different seedlings under the condition of completely closed clamping was obtained.By using ADAMS software,the dynamic simulation model of clamping and conveying mechanism was constructed,and the variation rules of different clamping force and rotation displacement of seedlings were analyzed.It was concluded that when the clamping force was less than 0.4 N,the seedlings were free from the bondage of the clamping hand.When the clamping force was greater than 3.5 N,the seedling clamping and rotating operation was stable.Based on the experimental results of mechanism performance,taking cucurbita moschata and cucumber as the test objects,the average success rate of the flexible gripper was 98.5%,which was 4.5 percentage points higher than that of the arc-shaped gripper,and the injury rate was reduced by 3.5 percentage points.The grafting speed of the mechanism was 1052 plants/h,which was 1.72 times of the production efficiency of the same type of single claw grafting machine.The grafting success rate was 96.67%,which greatly improved the production efficiency of grafting robot and met the needs of industrial grafting seedling production.The results can provide a technical reference for the design and optimization of the clamping and conveying mechanism of the high-speed grafting robot.