# Design and Testing of an End-Effector for Tomato Picking

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Materials and Methods

#### 2.1. Mechanistic Analysis of the Motion Characteristics of Tomato Picking End-Effectors

#### 2.2. Tomato Picking End-Effector Mechanical Structure Design and Calibration

#### 2.2.1. Determining the Size of the Tomato Picking End-Effector

#### 2.2.2. Strength Checking of the Key Parts

^{3}. Finite element analysis was performed on the fingertip, middle joint and base joint. The results are shown in Figure 8.

^{−2}mm, and the maximum stress was 37.2 MPa; the maximum strain of the middle joint was 1.504 × 10

^{−2}mm, and the maximum stress was 46.2 MPa; the maximum strain of the base joint was 1.504 × 10

^{−2}mm, and the maximum stress was 46.2. The yield strength of the Future 8000 resin was 47 MPa. These results show that the maximum stress was reached only locally, and the maximum stress in all three joints was less than the yield strength of the resin. Therefore, the Future 8000 resin could meet the strength requirements of the parts in tomato picking operations.

#### 2.2.3. Motor Performance Checking

#### 2.3. Kinematic Simulation Analysis of Tomato Picking End-Effector

#### 2.3.1. Kinematic Analysis

#### 2.3.2. Forward Kinematic Analysis

- Rotation of ${\alpha}_{i-1}$ angles around the ${X}_{i}$ axis;
- Translation along the ${X}_{i}$ axis by ${a}_{i-1}$ lengths;
- Rotation of ${\theta}_{i}$ angles around the ${Z}_{i}$ axis;
- Translation along the ${Z}_{i}$ axis by ${d}_{i}$ lengths.

#### 2.3.3. Inverse Kinematic Analysis

#### 2.3.4. Kinematic Simulation Verification

#### 2.4. Tomato Picking End-Effector Trajectory Planning and Workspace Simulation Verification

#### 2.4.1. Trajectory Planning

#### 2.4.2. Workspace Simulation Verification

## 3. Results

#### 3.1. Test Platform Construction

#### 3.2. Test and Result Analysis

## 4. Discussion

- Flexible joints could be added for the finger structure of the tomato picking end-effector. A suitable integrated driven joint motor could be selected to improve the compactness of the end-effector structure, yielding more of a bionic shape, size and movement.
- More accurate pressure sensors for contact force collection and more sensors on the end-effector, such as tactile sensors, joint displacement sensors, joint torque sensors, etc., could render the end-effector capable of humanoid picking in the greenhouse environment.
- The control algorithm of the end-effector could be optimized to equip the end-effector with multiple picking modes while also improving the picking efficiency and enhancing the flexibility and stability of the end-effector when grasping. The control system could also be optimized by adding the human–computer interaction interface for the convenience of user debugging.

## 5. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

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Serial Number | ${\mathit{\theta}}_{1}/\xb0$ | ${\mathit{\theta}}_{2}/\xb0$ | ${\mathit{\theta}}_{3}/\xb0$ | x | y | z |
---|---|---|---|---|---|---|

1 | 0 | 0 | 0 | 160.000 | 0 | 0 |

2 | 35 | 20 | 60 | 66.6590 | 119.8160 | 0 |

3 | 20 | 30 | 40 | 94.9488 | 106.4839 | 0 |

4 | 40 | 10 | 20 | 98.2107 | 122.1176 | 0 |

Given Angle | Forward Kinematics/mm | Inverse Kinematics/° | Inverse Kinematics/mm | ||||||||
---|---|---|---|---|---|---|---|---|---|---|---|

${\theta}_{1}$ | ${\theta}_{2}$ | ${\theta}_{3}$ | x | y | z | ${\theta}_{1}$ | ${\theta}_{2}$ | ${\theta}_{3}$ | x | y | z |

0 | 0 | 0 | 160.00 | 0 | 0 | 0 | 0 | 0 | 160.00 | 0 | 0 |

35 | 20 | 60 | 66.659 | 119.816 | 0 | 35.000 | 20.000 | 60.000 | 66.659 | 119.8160 | 0 |

20 | 30 | 40 | 94.949 | 106.484 | 0 | 20.000 | 30.000 | 40.000 | 94.949 | 106.484 | 0 |

40 | 10 | 20 | 98.211 | 122.117 | 0 | 39.999 | 10.000 | 19.999 | 98.211 | 122.118 | 0 |

Parameter | ${\mathit{d}}_{\mathit{i}0}$ | ${\mathit{\theta}}_{\mathit{i}0}$ | ${\mathit{\alpha}}_{\mathit{i}0}$ | ${\mathit{a}}_{\mathit{i}0}$ |
---|---|---|---|---|

Z_{10} | 0 | −120° | 90° | 40 |

Z_{20} | 0 | 120° | 90° | 40 |

Z_{30} | 0 | 0° | 90° | 40 |

Number | Large Diameter/mm | Small Diameter/mm | Height/mm | Weight/g |
---|---|---|---|---|

1 | 82.4 | 75.2 | 66.7 | 230 |

2 | 68.2 | 65.4 | 56.5 | 189 |

3 | 58.9 | 56.1 | 52.6 | 128 |

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## Share and Cite

**MDPI and ACS Style**

Wang, T.; Du, W.; Zeng, L.; Su, L.; Zhao, Y.; Gu, F.; Liu, L.; Chi, Q.
Design and Testing of an End-Effector for Tomato Picking. *Agronomy* **2023**, *13*, 947.
https://doi.org/10.3390/agronomy13030947

**AMA Style**

Wang T, Du W, Zeng L, Su L, Zhao Y, Gu F, Liu L, Chi Q.
Design and Testing of an End-Effector for Tomato Picking. *Agronomy*. 2023; 13(3):947.
https://doi.org/10.3390/agronomy13030947

**Chicago/Turabian Style**

Wang, Tianchi, Weiwei Du, Lingshen Zeng, Long Su, Yiming Zhao, Fang Gu, Li Liu, and Qian Chi.
2023. "Design and Testing of an End-Effector for Tomato Picking" *Agronomy* 13, no. 3: 947.
https://doi.org/10.3390/agronomy13030947