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Obtaining the effective gripper dimensions for a kiwifruit harvesting robot using kinematic calibration procedures
Industrial Robot ( IF 1.8 ) Pub Date : 2021-12-01 , DOI: 10.1108/ir-09-2021-0198
Chi Kit Au 1 , Michael Redstall 1 , Mike Duke 1 , Ye Chow Kuang 1 , Shen Hin Lim 1
Affiliation  

Purpose

A harvesting robot is developed as part of kiwifruit industry automation in New Zealand. This kiwifruit harvester is currently not economically viable, as it drops and damages too many kiwifruit in the harvesting task due to the positional inaccuracy of the gripper. This is due to the difficulties in measuring the exact effective dimensions of the gripper from the manipulator. The purpose of this study is to obtain the effective gripper dimensions using kinematic calibration procedures.

Design/methodology/approach

A setup of a constraint plate with a dial gauge is proposed to acquire the calibration data. The constraint plate is positioned above the robot. The data is obtained by using a dial gauge and a permanent marker. The effective dimensions of the gripper are used as error parameters in the calibration process. Calibration is exercised by minimizing the difference between target positions and measured positions iteratively.

Findings

The robot with the obtained effective dimensions is tested in the field. It is found that the fruit drops due to positional inaccuracy of the gripper are greatly reduced after calibration.

Practical implications

The kiwifruit industry in New Zealand is growing rapidly and announced plans in 2017 to double global sales by 2025. This growth will put extra pressure on the labour supply for harvesting. Furthermore, the Covid pandemic and resulting border restrictions have dramatically reduced seasonal imported labour availability. A robotic system is a potential solution to address the labour shortages for harvesting kiwifruit.

Originality/value

For kiwifruit harvesting, the picking envelope is well above the robot; the experimental data points obtained by placing a constraint plate above the robot are at similar positions to the target positions of kiwifruit. Using this set of data points for calibration yields a good effect of obtaining the effective dimension of the gripper, which reduces the positional inaccuracy as shown in the field test results.



中文翻译:

使用运动学校准程序获得猕猴桃收获机器人的有效夹持器尺寸

目的

作为新西兰猕猴桃产业自动化的一部分,开发了一种收获机器人。这种奇异果收割机目前在经济上不可行,因为在收获任务中,由于夹持器的位置不准确,它会掉落并损坏太多奇异果。这是由于难以从机械手测量夹具的准确有效尺寸。本研究的目的是使用运动学校准程序获得有效的夹具尺寸。

设计/方法/方法

提出了一种带有百分表的约束板的设置来获取校准数据。约束板位于机器人上方。数据是通过使用千分表和永久性标记获得的。夹具的有效尺寸用作校准过程中的误差参数。通过反复最小化目标位置和测量位置之间的差异来进行校准。

发现

对获得的有效尺寸的机器人进行了现场测试。校准后发现,由于夹持器位置不准确导致的果滴大大减少。

实际影响

新西兰的奇异果产业发展迅速,并在 2017 年宣布计划到 2025 年将全球销量翻一番。这种增长将给收获的劳动力供应带来额外压力。此外,Covid 大流行和由此产生的边境限制大大减少了季节性进口劳动力的供应。机器人系统是解决猕猴桃收获劳动力短缺的潜在解决方案。

原创性/价值

对于猕猴桃收获,采摘信封远高于机器人;通过在机器人上方放置约束板获得的实验数据点与猕猴桃的目标位置相似。使用这组数据点进行标定,可以很好地获得夹具的有效尺寸,降低了现场测试结果所示的位置不准确度。

更新日期:2021-12-01
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