摘要
穴盘草莓的长苗、大苗株特点和弓背向外的特殊移栽要求,使其自动化移栽存在困难。首先进行了草莓苗坨的单指刺入力和拔苗阻力试验,进而提出并开展了有约束苗坨的双指夹拔破坏试验。试验发现双针取苗指的苗坨刺入阻力与刺入速度、深度、含水率相关,50 mm和100 mm深度的最大刺入阻力分别可达21.47 N和57.09 N。双指的夹茎拔苗阻力可达9.64 N,而当取苗针滑移量为20 mm和40 mm时约束夹拔力分别可达10.85 N和42.5 N,但过大滑移量对精准可靠移栽极为不利。根据草莓穴盘苗的物理特性、苗坨的力学特性,设计了带双爪可同步换向变距的四针式移栽末端执行器。以有效缩减取苗爪宽度和摆动传动角为双重目标进行了多连杆定角斜插式双指四针取苗爪的非线性规划,得到了优化的机构参数。换向变距装置通过微型行程开关与微型电磁吸盘配合,实现了双取苗爪的快速同步换向变距和可靠定位。验证试验表明,在加速度不大于0.20 mm/s2时取出率和取苗成功率分别在93%和90%以上,加速度过大则可能造成取苗针滑脱和苗坨下部断裂,换向变距装置有效解决了弓背朝外问题和相邻两列同时移栽的间距调整问题,栽苗试验中放苗顺利且直立度和深度均达到移栽要求,且移栽后10 d草莓苗完全成活,该末端执行器可满足草莓穴盘苗的移栽作业需要。
Automatic transplanting of strawberry plug seedlings is difficult since both the plant and root lumps are much bigger and their arches must be kept outward when they are inserted into the soil and root. The inserting forces and extraction forces were tested, then a novel test of constrained extraction and the root lump rupture were designed and carried out. It was found that the inserting forces were related to speed, depth and moisture content, and the maximum inserting forces were 21.47 N and 57.09 N when the inserting depths were 50 mm and 100 mm, respectively. The maximum extraction force was 9.64 N, while the constrained extraction forces reached 10.85 N and 42.5 N when the fingers' sliding displacements were 20 mm and 40 mm, respectively, but big sliding displacement was not ideal for transplanting precisely. Based on physical and mechanical characteristics of strawberry plug seedlings got from the above tests, an end-effector for automatic transplanting was developed. The end-effector was composed of two grippers and one arch reversing mechanism. The gripper had two double-needle fingers and the inserting angle was fixed, which was helpful to realize large inserting depth in limited mechanism dimensions and avoid bruise and tearing of plants and root lumps, respectively. Taking reducing of gripper width and swing range of connecting rod as dual objectives, optimal mechanism parameters of the gripper were obtained by performing linear programming. The arch reversing mechanism transformed distance between seedlings form picking to placing and changed the arch orientation simultaneously with cooperated limit switches and electromagnets. The experiments showed that the successful rates of extraction and non-damage picking were above 93% and 90%, respectively, when the picking acceleration was no more than 0.20 m/s2. Otherwise,larger picking acceleration may lead to root lumps broken and fingers slid out. It was found that the arch reversing mechanism was able to transform distance between seedlings and change the arch orientation precisely. Finally, all seedlings were inserted into pre- punched holes successfully and depth and upright degree were qualified, and survival rate reached 100% after 10 d of transplanting. This novel end-effector was proved to be able to satisfy the need of automatic transplanting of strawberry plug seedlings.
出处
《农业机械学报》
EI
CAS
CSCD
北大核心
2016年第11期49-58,共10页
Transactions of the Chinese Society for Agricultural Machinery
基金
江苏省农业科技支撑重点项目(BE2014406)
中国博士后科学基金项目(2012M521013)
江苏省农业科技自主创新资金项目(CX16-1044)
江苏高校优势学科建设工程项目(PAPD)
关键词
草莓
穴盘苗
移栽
末端执行器
strawberry
plug seedling
transplant
end-effector