Force Analysis and Experiment of Variable Stiffness Soft Actuator Based on Particle Jamming

Actuators with variable stiffness have vast potential in the field of compliant robotics. Morphological shape changes in the actuators are possible, while they retain their structural strength. They can shift between a rigid load-carrying state and a soft flexible state in a short transition period. This work presents a hydraulically actuated soft actuator fabricated by a fully 3D printing of shape memory polymer (SMP). The actuator shows a stiffness of 519 mN/mm at 20 ∘C and 45 mN/mm at 50 ∘C at the same pressure (0.2 MPa). This actuator demonstrates a high stiffness variation of 474 mN/mm (10 times the baseline stiffness) for a temperature change of 30 ∘C and a large variation (≈1150%) in average stiffness. A combined variation of both temperature (20–50 ∘C) and pressure (0–0.2 MPa) displays a stiffness variation of 501 mN/mm. The pressure variation (0–0.2 MPa) in the actuator also shows a large variation in the output force (1.46 N) at 50 ∘C compared to the output force variation (0.16 N) at 20 ∘C. The pressure variation is further utilized for bending the actuator. Varying the pressure (0–0.2 MPa) at 20 ∘C displayed no bending in the actuator. In contrast, the same variation of pressure at 50 ∘C displayed a bending angle of 80∘. A combined variation of both temperature (20–50 ∘C) and pressure (0–0.2 MPa) shows the ability to bend 80∘. At the same time, an additional weight (300 g) suspended to the actuator could increase its bending capability to 160∘. We demonstrated a soft robotic gripper varying its stiffness to carry objects (≈100 g) using two individual actuators.

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A Programmable Mechanical Freedom and Variable Stiffness Soft Actuator with Low Melting Point Alloy

Intelligent Robotics and Applications - Lecture Notes in Computer Science ◽

10.1007/978-3-319-65289-4_15 ◽

2017 ◽

pp. 151-161 ◽

Cited By ~ 6

Author(s):

Yufei Hao ◽

Tianmiao Wang ◽

Li Wen

Keyword(s):

Melting Point ◽

Variable Stiffness ◽

Soft Actuator

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Soft Actuator Model for a Soft Robot With Variable Stiffness by Coupling Pneumatic Structure and Jamming Mechanism

IEEE Access ◽

10.1109/access.2020.2968928 ◽

2020 ◽

Vol 8 ◽

pp. 26356-26371 ◽

Cited By ~ 1

Author(s):

Feng-Yu Xu ◽

Feng-You Jiang ◽

Quan-Sheng Jiang ◽

Yu-Xuan Lu

Keyword(s):

Variable Stiffness ◽

Soft Robot ◽

Soft Actuator

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Design and Characterisation of a Variable Stiffness Soft Actuator Based on Tendon Twisting

10.1007/978-3-030-89177-0_42 ◽

2021 ◽

pp. 402-407

Author(s):

William King ◽

Luke Pooley ◽

Philip Johnson ◽

Khaled Elgeneidy

Keyword(s):

Variable Stiffness ◽

Soft Actuator

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Echinoderm Inspired Variable Stiffness Soft Actuator with Connected Ossicle Structure

2019 International Conference on Robotics and Automation (ICRA) ◽

10.1109/icra.2019.8793545 ◽

2019 ◽

Cited By ~ 1

Author(s):

Hwayeong Jeong ◽

Jung Kim

Keyword(s):

Variable Stiffness ◽

Soft Actuator

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Novel Design and Modeling of a Soft Pneumatic Actuator Based on Antagonism Mechanism

Actuators ◽

10.3390/act9040107 ◽

2020 ◽

Vol 9 (4) ◽

pp. 107

Author(s):

Yinglong Chen ◽

Junhao Zhang ◽

Yongjun Gong

Keyword(s):

Mechanical Characteristics ◽

Artificial Muscle ◽

Variable Stiffness ◽

Pneumatic Artificial Muscle ◽

Human Machine Interaction ◽

Soft Actuator ◽

Stiffness Characteristics ◽

Machine Interaction ◽

Novel Design ◽

Compound Action

The soft actuator possesses the characteristics of flexibility, environmental adaptability, and human–machine interaction. Firstly, aiming to resolve the limitation of variable stiffness performance of a traditional pneumatic artificial muscle (PAM) actuator, based on the antagonistic mechanism of extensor and contractor muscles, a novel pneumatic soft actuator coupled of extensor and contractor muscles is proposed in this paper. The actuator can perform the compound action of elongation/contraction, and the stiffness of it can be controlled by adjusting the elongation and contraction forces. Secondly, based on the deformation principle of woven and elastic fabric layers, the mechanical characteristics model of the actuator is established and simulated. The mechanical properties of the actuator are tested under different pressures and deformation displacement and the variable stiffness characteristics of the actuator are verified. Finally, actuators are utilized to manufacture a soft mechanical manipulator, which can achieve variable stiffness in a fixed bending attitude.

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