# Grasping Profile Control of a Soft Pneumatic Robotic Gripper for Delicate Gripping

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## Abstract

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## 1. Introduction

- The design of an actuator set for controlling the SPG, comprising an air compressor pump with digital regulators and a pneumatic cylinder actuator along with its associated accessories.
- The development of a control technique that is capable of estimating unknown inputs of the system and effectively regulating the pressure and volume within the system.

## 2. Materials and Methods

#### 2.1. The System Architecture of Soft Pneumatic Gripper

#### 2.2. Dynamic Model and Control Technique for the System

#### 2.2.1. Dynamic Model of the System

#### 2.2.2. Unknown Input Observer

#### 2.2.3. Control Technique

## 3. Experimental Results and Discussion

#### 3.1. The Simulation Results of Unknown Input Observer

#### 3.2. Experimental Results of the System

#### 3.3. Discussion

## 4. Conclusions

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 3.**Soft pneumatic gripper: (

**a**) example of soft pneumatic gripper mold; (

**b**) silicone soft pneumatic gripper.

**Figure 4.**The free body diagram of the components: (

**a**) free body diagram of the pneumatic cylinder; (

**b**) free body diagram of the SPG.

**Figure 6.**Variation in initial volumes in the SPG: (

**a**) the setup used to verify the initial volumes in the SPG with water; (

**b**) the relationship between pressure and SPG volume.

**Figure 12.**SPG volume tracking response with the target volume and different inertial pressures of the system. (Red: Initial Pressure = 0.00 Bars, Blue: Initial Pressure = 0.05 Bars, Green: Initial Pressure = 0.08 Bars, Black: Initial Pressure = 0.13 Bars: Cyan: Initial Pressure = 0.16 Bars).

Components | Parameters | Value | Unit |
---|---|---|---|

Pneumatic Cylinder | Volume, ${v}_{1}$ | 25.5 | $\mathrm{mL}$ |

Cross-Section Area of the Piston, ${A}_{1}$ | 16.67 | ${\mathrm{mm}}^{2}$ | |

Mass of the Piston, $m$ | 0.736 | $\mathrm{kg}$ | |

Stroke Length | 153 | $\mathrm{mm}$ | |

SPG | Volume, ${v}_{2}$ @1atm | 23.6 | $\mathrm{mL}$ |

Mass of the Gripper | 0.1 | kg | |

DC Motor | Moment of Inertia of the Rotor, $J$ | $4.73\times {10}^{-5}$ | $\mathrm{kg}\xb7{\mathrm{m}}^{2}$ |

Electric Resistance, $R$ | 0.9 | $\mathrm{ohm}$ | |

Electric Inductance, $L$ | $3.6\times {10}^{-3}$ | $\mathrm{H}$ | |

Electromotive Force Constant, ${K}_{e}$ | $80\times {10}^{-3}$ | $\mathrm{N}\xb7\mathrm{m}/\mathrm{A}$ | |

Motor Torque Constant, ${K}_{t}$ | $80\times {10}^{-3}$ | $\mathrm{N}\xb7\mathrm{m}/\mathrm{A}$ | |

Linear Stage | Pitch of the Ball Screw, $l$ | $\mathrm{mm}$ | |

Efficiencies of the Thread of Ball Screw, ${\eta}_{thread}$ | 0.9 | ||

Efficiencies of the Thrust Bearing of Ball Screw, ${\eta}_{thrust}$ | 0.9 | ||

Encoder | Pulse per Revolution | 4000 | $\mathrm{ppr}$ |

1 Pulse of Encoder | 0.006375 | $\mathrm{mm}$ | |

The System | Dead Volume | 17.15 | $\mathrm{mL}$ |

Atmospheric Pressure | 1 | $\mathrm{Bar}$ |

Gripper Volume Setting via a Syringe (mL) | Gripper Distance, D (mm) | ||||
---|---|---|---|---|---|

Gripper Distance with Syringe Pressure Control | $\mathbf{Initial}\mathit{p}=0\mathbf{bar}$ | $\mathbf{Initial}\mathit{p}=0.5\mathbf{bar}$ | $\mathbf{Initial}\mathit{p}=1\mathbf{bar}$ | $\mathbf{Initial}\mathit{p}=1.5\mathbf{bar}$ | |

24 | 48.5 | 42.0 | - | - | - |

25 | 30.0 | 33.1 | - | - | - |

27 | 23.4 | 22.3 | 22.2 | - | - |

29 | 16.9 | 14.4 | 15.8 | 17.3 | - |

31 | 9.7 | 6.2 | 9.3 | 9.7 | 10.5 |

33 | 3.7 | 0 | 3.2 | 2.6 | 3.7 |

36 | 0 | 0 | 0 | 0 | 0 |

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## Share and Cite

**MDPI and ACS Style**

Phanomchoeng, G.; Pitchayawetwongsa, P.; Boonchumanee, N.; Lin, S.; Chancharoen, R.
Grasping Profile Control of a Soft Pneumatic Robotic Gripper for Delicate Gripping. *Robotics* **2023**, *12*, 107.
https://doi.org/10.3390/robotics12040107

**AMA Style**

Phanomchoeng G, Pitchayawetwongsa P, Boonchumanee N, Lin S, Chancharoen R.
Grasping Profile Control of a Soft Pneumatic Robotic Gripper for Delicate Gripping. *Robotics*. 2023; 12(4):107.
https://doi.org/10.3390/robotics12040107

**Chicago/Turabian Style**

Phanomchoeng, Gridsada, Patchara Pitchayawetwongsa, Nattaphat Boonchumanee, Saravut Lin, and Ratchatin Chancharoen.
2023. "Grasping Profile Control of a Soft Pneumatic Robotic Gripper for Delicate Gripping" *Robotics* 12, no. 4: 107.
https://doi.org/10.3390/robotics12040107