椭圆夹爪剪切式火龙果采摘末端执行器设计

doi:10.13304/j.nykjdb.2023.0937

摘要/Abstract

摘要：

针对火龙果生长环境复杂、生长姿态多样、枝条内茎剪切强度大、果蒂附近果皮易损伤等采摘难题，设计了一种椭圆夹爪剪切式火龙果采摘末端执行器，能够对不同生长姿态下的火龙果进行无损采摘。椭圆夹爪可以将火龙果果实与枝条分隔，保护果实的完整；通过在椭圆夹爪上开V型槽来适应不同倾角的火龙果，防止枝条对夹持动作的阻碍；采用先剪后拉的方法采摘火龙果。对夹持和剪切机构进行力学分析，通过剪切试验测得最小剪切力为33.5 N，对动力源进行选型。建立了剪切后火龙果拉力采摘模型，经过有限元分析和果园人工剪切后的拉力试验对比，测得平均拉力为20 N，不会对果实造成损伤。构建了物理样机，并对其进行了15次夹持试验和25次果园实地剪切试验，结果表明，末端执行器的可采摘范围远大于现有火龙果定位精度，采摘火龙果倾角为50°~90°，平均采摘时间为3.1 s，采摘成功率为92%，切下的叶片平均长度为55.3 mm，能够满足采摘需求。

关键词: 末端执行器, 火龙果, 椭圆夹爪, 剪切式, 性能试验

Abstract:

Aiming at the difficultly picking problems of dragon fruit， such as complex growing environment， diverse growth posture， high shear strength of stems in branches and easily damaging peel near fruit pedicle， a kind of cutting end effector of dragon fruit picking based on oval claw was designed to pick dragon fruit in different growing posture without damage. The elliptical grippers were capable of separating the fruit from the branches， thus protecting the integrity of the fruit. By incorporating V-shaped grooves on the elliptical grippers， it accommodated dragon fruits with different inclinations， preventing obstacles from branches during gripping actions. The dragon fruit harvesting method adopted a pre-cut and pull approach. Mechanical analysis of the gripping and cutting mechanism determined the minimum cutting force to be 33.5 N， and appropriate power sources were selected accordingly. A model for the pulling force during dragon fruit harvesting after cutting was established. Through finite element analysis and comparison with manual cutting force tests in the orchard， an average pulling force of 20 N was measured， which did not damage the fruit. A physical prototype was constructed and subjected to 15 gripping experiments and 25 field cutting trials in the orchard. Experimental results demonstrated that the harvesting range of the end effector surpasses the existing dragon fruit positioning accuracy significantly. The end effector can harvest dragon fruits with inclinations ranging from 50° to 90° with an average inclination of 75°， the average harvesting time is 3.1 s with a success rate of 92%， the average length of the cut leaves was 55.3 mm， which could meet the picking demand.

Key words: end effector, dragon fruit, elliptical grippers, shear-type, performance testing

中图分类号:

TP242.6

陈桥, 肖明玮, 罗陈迪, 高嘉正, 欧阳春凡, 曾春林, 李文涛, 周学成. 椭圆夹爪剪切式火龙果采摘末端执行器设计[J]. 中国农业科技导报, 2025, 27(5): 113-121.

Qiao CHEN, Mingwei XIAO, Chendi LUO, Jiazheng GAO, Chunfan OUYANG, Chunlin ZENG, Wentao LI, Xuecheng ZHOU. Design of Shear End Effector for Dragon Fruit Picking Based on Oval Claw[J]. Journal of Agricultural Science and Technology, 2025, 27(5): 113-121.

图/表 11

图1 火龙果采摘末端执行器机构注：1—剪刀；2—连杆；3—剪切驱动齿轮；4—剪切驱动舵机；5—手腕连接件；6—夹持驱动舵机；7—剪切驱动齿轮；8—椭圆夹爪。

Fig. 1 Structure of the end effector of dragon fruit pickingNote：1—Scissors； 2—Connecting rod； 3—Gear wheel； 4—Steering engine； 5—Mechanical arm connector； 6—Steering engine； 7—Gear wheel； 8—Oval jaw.

图2 椭圆夹爪结构

Fig. 2 Oval claw structure

图3 夹持机构力学分析

Fig. 3 Mechanical analysis of clamping mechanism

图4 剪切机构力学分析

Fig. 4 Mechanical analysis diagram of shear mechanism

图5 火龙果与夹爪相对位置

Fig. 5 Relative position of dragon fruit and claw

图6 剪刀水平速度和角速度变化曲线

Fig. 6 Horizontal and angular velocity curves of scissors

图7 剪刀水平加速度和角加速度变化曲线

Fig. 7 Curve of horizontal and angularacceleration of scissors

表1 火龙果单刀剪切试验结果

Table 1 Results of single knife shear test of dragon fruit

序号 Number	果梗直径 Stem diameter/mm	加载速度Loading speed/ （mm·min^-1）	最大剪切力 Maximum shear force/N
1	4.24	10	35.64
2	5.24	10	46.67
3	5.47	10	44.89
4	4.56	10	67.10
5	4.05	10	38.03
6	4.5	10	34.56
7	4.05	20	38.17
8	5.23	20	63.82
9	5.10	20	46.38
10	4.65	20	47.12
11	4.70	20	51.89
12	4.53	20	44.23
13	4.10	50	32.06
14	4.93	50	61.29
15	5.04	50	45.78
16	4.91	50	43.84
17	4.83	50	39.37
18	4.48	50	48.46
19	4.11	80	35.04
20	4.90	80	46.97
21	4.95	80	43.54
22	5.10	80	41.60
23	4.63	80	44.44
24	4.20	80	48.46

图8 剪切后的火龙果受拉的应力应变分布A：等效应变分布；B：垂直受拉应力分布

Fig. 8 Stress-strain distribution of the strained dragon fruit after shearA： Equivalent strain distribution； B：Vertical tensile stress

表2 切后火龙果拉力测量试验结果

Table 2 Test results of cutting dragon fruit tension

序号 Number	果实尺寸 Fruit size/mm	切痕长度 Cut length/mm	拉力 Tension/N	叶片组织长度 Leaf tissue length/mm
1	63.7×81.0	43.3	16.0	58.4
2	67.3×76.3	45.4	25.5	40.7
3	61.0×73.6	49.0	25.5	40.8
4	73.4×90.3	54.2	22.0	54.1
5	66.2×93.1	47.2	18.0	33.1
6	70.8×81.1	50.1	22.5	58.9
7	62.0×78.4	46.8	18.0	41.6
8	64.5×77.0	54.2	17.0	38.3
9	61.0×71.1	46.5	20.0	45.4
10	71.5×79.8	58.0	23.0	63.7
11	83.0×100.5	47.4	21.0	43.1
12	86.0×104.0	51.3	19.0	53.6
13	87.0×105.1	55.2	23.5	59.4
14	89.0×107.3	48.1	22.0	55.3
15	78.3×99.4	45.3	16.5	32.5
16	75.8×94.2	40.6	20.5	41.7
17	70.0×90.0	52.1	17.5	53.7
18	73.0×92.0	46.2	15.5	32.1
19	67.0×88.1	44.3	17.0	47.6
20	64.5×84.3	43.5	19.5	46.3

表3 采摘范围试验结果

Table 3 Clamp test results

尺寸

Size/mm

数量

Quantity

+x方向

+x direction/mm

+y方向

+y direction/mm

+z方向 +z direction/ mm

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