Research on Flexible End-Effectors with Humanoid Grasp Function for Small Spherical Fruit Picking

Fu Zhang (), Zijun Chen, Yafei Wang, Ruofei Bao, Xingguang Chen, Sanling Fu, Mimi Tian and Yakun Zhang
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Fu Zhang: College of Agricultural Equipment Engineering, Henan University of Science and Technology, Luoyang 471003, China
Zijun Chen: College of Agricultural Equipment Engineering, Henan University of Science and Technology, Luoyang 471003, China
Yafei Wang: Key Laboratory of Modern Agricultural Equipment and Technology, Ministry of Education, Jiangsu University, Zhenjiang 212013, China
Ruofei Bao: College of Agricultural Equipment Engineering, Henan University of Science and Technology, Luoyang 471003, China
Xingguang Chen: College of Agricultural Equipment Engineering, Henan University of Science and Technology, Luoyang 471003, China
Sanling Fu: College of Physical Engineering, Henan University of Science and Technology, Luoyang 471023, China
Mimi Tian: College of Agricultural Equipment Engineering, Henan University of Science and Technology, Luoyang 471003, China
Yakun Zhang: College of Agricultural Equipment Engineering, Henan University of Science and Technology, Luoyang 471003, China

Agriculture, 2023, vol. 13, issue 1, 1-18

Abstract: The rapid, stable, and undamaged picking of small-sized spherical fruits are one of the key technologies to improve the level of intelligent picking robots and reduce grading operations. Cherry tomatoes were selected as the research object in this work. Picking strategies of two-stage “Holding-Rotating” and finger-end grasping were determined. The end-effector was designed to separate the fruit from the stalk based on the linear motion of the constraint part and the rotating gripper. This work first studied the human hand-grasping of cherry tomatoes and designed the fingers with sinusoidal characteristics. The mathematical model of a single finger of the gripper was established. The structural parameters of the gripper were determined to meet the requirements of the grabbing range from 0 to 61.6 mm. Based on the simulation model, the constraint part was set to 6 speeds, and the fruit sizes were set to 20 mm, 30 mm, and 40 mm, respectively. When the speed was 0.08m/s, the results showed that the grabbing time was 0.5381 s, 0.387 s, and 0.2761 s, respectively, and the maximum grabbing force was 0.9717 N, 3.5077 N, and 4.0003 N now of clamping, respectively. It met the picking requirements of high speed and low loss. The criterions of two-index stability and undamaged were proposed, including the grasping index of the fixed value and the slip detection of variance to mean ratio. Therefore, the control strategy and algorithm based on two-stage and two-index for rapid, stable, and non-destructive harvesting of small fruit were proposed. The results of the picking experiment for seventy-two cherry tomatoes showed that the picking success rate was 95.82%, the average picking time was 4.86 s, the picking damage rate was 2.90%, the browning rate was 2.90% in 72 h, and the wrinkling rate was 1.49% in 72 h, which can meet the actual small spherical fruit picking requirements. The research will provide an idea for the flexible end-effectors with humanoid grasp function and provides a theoretical reference for small spherical fruit picking.

Keywords: small spherical fruits; end-effector; design; mathematical model; 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: 2023
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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