A Soft Gripper Design for Apple Harvesting with Force Feedback and Fruit Slip Detection

Kaiwen Chen, Tao Li (), Tongjie Yan, Feng Xie, Qingchun Feng, Qingzhen Zhu and Chunjiang Zhao ()
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Kaiwen Chen: School of Agricultural Equipment Engineering, Jiangsu University, Zhenjiang 212013, China
Tao Li: Intelligent Equipment Research Center, Beijing Academy of Agriculture and Forestry Sciences, Beijing 100097, China
Tongjie Yan: School of Agricultural Equipment Engineering, Jiangsu University, Zhenjiang 212013, China
Feng Xie: School of Agricultural Equipment Engineering, Jiangsu University, Zhenjiang 212013, China
Qingchun Feng: Intelligent Equipment Research Center, Beijing Academy of Agriculture and Forestry Sciences, Beijing 100097, China
Qingzhen Zhu: School of Agricultural Equipment Engineering, Jiangsu University, Zhenjiang 212013, China
Chunjiang Zhao: National Engineering Research Center for Information Technology in Agriculture, Beijing 100097, China

Agriculture, 2022, vol. 12, issue 11, 1-26

Abstract: This research presents a soft gripper for apple harvesting to provide constant-pressure clamping and avoid fruit damage during slippage, to reduce the potential danger of damage to the apple pericarp during robotic harvesting. First, a three-finger gripper based on the Fin Ray structure is developed, and the influence of varied structure parameters during gripping is discussed accordingly. Second, we develop a mechanical model of the suggested servo-driven soft gripper based on the mappings of gripping force, pulling force, and servo torque. Third, a real-time control strategy for the servo is proposed, to monitor the relative position relationship between the gripper and the fruit by an ultrasonic sensor to avoid damage from the slip between the fruit and fingers. The experimental results show that the proposed soft gripper can non-destructively grasp and separate apples. In outdoor orchard experiments, the damage rate for the grasping experiments of the gripper with the force feedback system turned on was 0%; while the force feedback system was turned off, the damage rate was 20%, averaged for slight and severe damage. The three cases of rigid fingers and soft fingers with or without slip detection under the gripper structure of this study were tested by picking 25 apple samples for each set of experiments. The picking success rate for the rigid fingers was 100% but with a damage rate of 16%; the picking success rate for soft fingers with slip detection was 80%, with no fruit skin damage; in contrast, the picking success rate for soft fingers with slip detection off increased to 96%, and the damage rate was up to 8%. The experimental results demonstrated the effectiveness of the proposed control method.

Keywords: apple harvesting; soft gripper; Fin Ray effect; finite element analysis; constant-pressure feedback; slip detection (search for similar items in EconPapers)
JEL-codes: Q1 Q10 Q11 Q12 Q13 Q14 Q15 Q16 Q17 Q18 (search for similar items in EconPapers)
Date: 2022
References: View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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