# Monkeybot: A Climbing and Pruning Robot for Standing Trees in Fast-Growing Forests

^{1}

^{2}

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Mechanical Structure

#### 2.1. Clamping Mechanism

#### Clamping Force Estimation

_{1}is the pusher cylinder thrust; F

_{N}

_{3}is the clamping force of the clamping wheel.

_{1}and F

_{N}

_{3}can be obtained by solving for:

_{f}is the friction; μ is the friction coefficient, 0.1; F

_{N}is the clamping force; m is the mass of the whole machine, 41.25 kg; and g is gravitational acceleration, 9.8 m/s

^{2}.

_{1}= 2021.25 N can be found through the association of Equations (2)–(4), that is, the clamping force should be greater than 2021.25 N.

#### 2.2. Cutting Mechanism

#### Estimation of Cutting Force and Cutting Power

^{2}; h is the cutting thickness; δ is the cutting angle, 21°; v is the feed rate, 3 m/s; C

_{ρ}is the tool edge passivation coefficient, 1; k, A, B, and C

_{Z}are the correction factors.

_{Z}correction factors are derived from Equations (7)–(10), and each parameter can be obtained by consulting the literature [22].

_{1}= 1.46 N/mm, k

_{2}= 4.81 N/mm, A

_{1}= 0.196 N/mm

^{2}, A

_{2}= 0.549 N/mm

^{2}, B

_{1}= 0.069 N/mm

^{2}, B

_{2}= 0.200 N/mm

^{2}, C

_{1}= 5.396 N/mm

^{2}and C

_{2}= 19.620 N/mm

^{2}

_{x}can be derived from Equations (11) and (12).

_{c}can be derived from Equation (13).

_{x}= 2832.32 N, and P

_{c}= 8.50 kW.

#### 2.3. Traveling Mechanism

#### Estimation of Drive Power

_{d}required by the Monkeybot in the working process includes the power P

_{a}consumed by overcoming gravity, the power loss P

_{b}caused by the climbing resistance, and the power P

_{c}consumed by cutting, whose relationship is shown in Equation (14).

_{a}consumed to overcome gravity is given by Equation (15).

_{b}caused by the climbing resistance is given by Equation (16).

_{1}is the hydraulic motor and the main wheel transmission efficiency, 0.98; η

_{2}is the coupling transmission efficiency, 0.95; η

_{3}is the 1:1 bevel gear right-angle commutator transmission efficiency, 0.90.

#### 2.4. Barrier Avoidance Mechanism

## 3. Control System

#### 3.1. Hydraulic and Pneumatic System

#### 3.2. Ground Station

#### 3.3. Human-Machine Interaction Terminal

## 4. Optimized Design

#### 4.1. Experimental Principles and Methods

#### 4.2. Experimental Protocol and Analysis of Results

#### 4.2.1. Experimental Protocol

_{1}, the tool edge angle as X

_{2}, the cutting speed as X

_{3}, and the assessment index was the maximum shear stress p. Based on the Box–Behnken experimental design method [25,26], the test factor coding of the three-factor three-level orthogonal test is shown in Table 2.

#### 4.2.2. Analysis of Variance

^{2}= 0.9890, indicating that 98.90% of the variation in the maximum shear stress originates from the test factor. The model signal-to-noise ratio is 26.8119, which is greater than 4, indicating that the model is better and can be used for parameter optimization. Items x

_{1}, x

_{2}, x

_{3}, and x

_{22}were highly significant (p < 0.01), items x

_{1}x

_{2}, x

_{2}, and x

_{3}were significant (p < 0.05), and the remaining items were insignificant. The order of the effects of the test factors on the maximum shear stress was X

_{1}> X

_{2}> X

_{3}, and the simplified regression equation was obtained by eliminating the insignificant items in Equation (19) as in Equation (20).

#### 4.2.3. Analysis of the Influence Pattern of Interaction Factors on Indicators

#### 4.2.4. Parameter Optimization and Verification

## 5. Performance Evaluation

## 6. Conclusions

## 7. Patents

## Author Contributions

## Funding

## Data Availability Statement

## Conflicts of Interest

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**Figure 1.**Monkeybot: 1—frame; 2—walking mechanism; 3—clamping mechanism; 4—cutting mechanism; 5—obstacle avoidance mechanism.

**Figure 6.**Traveling mechanism: 1—rubber track; 2—main wheel; 3—support wheel; 4—tensioning wheel; 5—1:1 bevel gear right-angle commutator; 6—hydraulic motor.

**Figure 7.**Obstacle avoidance mechanism. (

**a**) Normal working conditions; (

**b**) working conditions when passing obstacles.

**Figure 9.**Hydraulic and pneumatic principles: 1—hydraulic Station; 2—pressure-reducing valve; 3— variable throttle valve; 4—PID control; 5—three-position four-way directional valve; 6—hydraulic lock; 7—hydraulic motor; 8—encoder; 9—air compressor; 10—one-way valve; 11—two-position four-way directional valve; 12—proportional pressure-reducing valve; 13—pressure sensors; 14—clamping cylinder; 15—barrier avoidance cylinder; 16—oscillating cylinder.

**Figure 10.**Ground station control principle: 1—Monkeybot; 2—electric hydraulic pneumatic integrated pipeline; 3—hydraulic station; 4—electric control box; 5—generator; 6—tree trunk.

**Figure 13.**Response surface of interaction factors to maximum shear stress. (

**a**) $\sigma =f\left({X}_{1},{X}_{2},3.25\right)$; (

**b**) $\sigma =f\left({X}_{1},22.5,{X}_{3}\right)$; (

**c**) $\sigma =f\left(2,{X}_{2},{X}_{3}\right)$.

Geometrical Structures | Density/ (kg·m ^{−3}) | Young’s Modulus (GPa) | Poisson’s Ratio |
---|---|---|---|

Cutting tool | 7850 | 200 | 0.3 |

Twig | 605 | 1.6 | 0.3 |

Tree trunk | 639 | 2.0 | 0.3 |

Level | Factor | ||
---|---|---|---|

Tool–Trunk Clearance X _{1} (cm) | Cutting Edge Angle X_{2} (°) | Cutting Speed X _{3} (m·s^{−1}) | |

−1 | 1.00 | 15.00 | 2.50 |

0 | 2.00 | 22.50 | 3.25 |

1 | 3.00 | 30.00 | 4.00 |

No. | X_{1} | X_{2} | X_{3} | η |
---|---|---|---|---|

1 | −1 | 0 | −1 | 1.1763 |

2 | −1 | −1 | 0 | 1.4849 |

3 | 0 | 0 | 0 | 1.3372 |

4 | 0 | 1 | 1 | 1.7973 |

5 | 0 | 1 | −1 | 1.6884 |

6 | 0 | -1 | 1 | 1.7228 |

7 | 0 | 0 | 0 | 1.3677 |

8 | 1 | 1 | 0 | 1.7053 |

9 | −1 | 0 | 1 | 1.4313 |

10 | −1 | 1 | 0 | 1.6611 |

11 | 0 | 0 | 0 | 1.3594 |

12 | 0 | 0 | 0 | 1.3452 |

13 | 1 | −1 | 0 | 1.6837 |

14 | 1 | 0 | −1 | 1.2611 |

15 | 0 | −1 | −1 | 1.4287 |

16 | 1 | 0 | 1 | 1.5023 |

17 | 0 | 0 | 0 | 1.3116 |

Variance Sources | Some of Deviations Squares | Freedom of Degree | Mean Square | F | P |
---|---|---|---|---|---|

Model | 0.5610 | 9 | 0.0623 | 69.72 | <0.0001 ** |

x_{1} | 0.0199 | 1 | 0.0199 | 22.24 | 0.0022 ** |

x_{2} | 0.0354 | 1 | 0.0354 | 39.57 | 0.0004 ** |

x_{3} | 0.1011 | 1 | 0.1011 | 113.06 | <0.0001 ** |

x_{1} x_{2} | 0.0060 | 1 | 0.0060 | 6.68 | 0.0362 * |

x_{1} x_{3} | 0.0000 | 1 | 0.0000 | 0.0533 | 0.8241 |

x_{2} x_{3} | 0.0086 | 1 | 0.0086 | 9.59 | 0.0174 * |

x_{12} | 0.0008 | 1 | 0.0008 | 0.8596 | 0.3847 |

x_{22} | 0.3867 | 1 | 0.3867 | 432.52 | <0.0001 ** |

x_{32} | 0.0006 | 1 | 0.0006 | 0.6827 | 0.4359 |

Residual | 0.0063 | 7 | 0.0009 | ||

Lack of fit | 0.0044 | 3 | 0.0015 | 3.07 | 0.1536 |

Pure Error | 0.0019 | 4 | 0.0005 | ||

Total | 0.5672 | 16 |

_{1}, x

_{2}, and x

_{3}are the level values of X

_{1}, X

_{2}, and X

_{3}. * means the influence is significant, p < 0.05; ** means the influence is highly significant, p < 0.01.

Diameter at Breast Height /cm | Number of Tests | Average Operating Time for a Single Tree (s) | Maximum Climbing Height (m) | Maximum Pruning Diameter (cm) | Overall Pruning Effect | |||||
---|---|---|---|---|---|---|---|---|---|---|

Late Spring | Winter | Late Spring | Winter | Late Spring | Winter | Late Spring | Winter | Late Spring | Winter | |

10~12 | 5 | 5 | 25.42 | 22.32 | 4.32 | 5.88 | 1.95 | 2.21 | Flattening | Flattening |

12~14 | 5 | 5 | 26.51 | 23.98 | 4.73 | 6.32 | 2.13 | 2.34 | Flattening | Flattening |

14~16 | 5 | 5 | 28.33 | 27.11 | 5.82 | 6.83 | 2.33 | 2.58 | Slight Splitting | Flattening |

16~18 | 5 | 5 | 28.90 | 26.74 | 6.03 | 7.18 | 2.61 | 2.79 | Slight Splitting | Slight Splitting |

18~20 | 5 | 5 | 26.87 | 24.83 | 5.23 | 6.40 | 2.31 | 2.49 | Splitting | Splitting |

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## Share and Cite

**MDPI and ACS Style**

Ban, Y.; Lyu, K.; Ba, S.; Wen, J.; Kang, F.; Li, W.
Monkeybot: A Climbing and Pruning Robot for Standing Trees in Fast-Growing Forests. *Actuators* **2022**, *11*, 287.
https://doi.org/10.3390/act11100287

**AMA Style**

Ban Y, Lyu K, Ba S, Wen J, Kang F, Li W.
Monkeybot: A Climbing and Pruning Robot for Standing Trees in Fast-Growing Forests. *Actuators*. 2022; 11(10):287.
https://doi.org/10.3390/act11100287

**Chicago/Turabian Style**

Ban, Yichen, Kun Lyu, Shihong Ba, Jian Wen, Feng Kang, and Wenbin Li.
2022. "Monkeybot: A Climbing and Pruning Robot for Standing Trees in Fast-Growing Forests" *Actuators* 11, no. 10: 287.
https://doi.org/10.3390/act11100287