Actuators

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27 pages, 4360 KiB

Open AccessArticle

Photogrammetric Measurement and Analysis of the Shape Profile of Pneumatic Artificial Muscles

by Jonathan M. Chambers and Norman M. Wereley

Actuators 2021, 10(4), 72; https://0-doi-org.brum.beds.ac.uk/10.3390/act10040072 - 06 Apr 2021

Cited by 5 | Viewed by 2921

Abstract

Inaccuracies in modeling of the geometric shape of PAMs has long been cited as a probable source of error in modeling and design efforts. The geometric shape and volume of PAMs is commonly approximated using a cylindrical shape profile, even though its shape [...] Read more.

Inaccuracies in modeling of the geometric shape of PAMs has long been cited as a probable source of error in modeling and design efforts. The geometric shape and volume of PAMs is commonly approximated using a cylindrical shape profile, even though its shape is non-cylindrical. Correction factors—based on qualitative observations of the PAM’s general shape—are often implemented to compensate for error in this cylindrical shape approximation. However, there is little evidence or consensus on the accuracy and form of these correction factors. Approximations of the shape profile are also used to calculate the internal volume of PAMs, as experimental measurements of the internal volume require intrusive testing methods and specialized equipment. This research presents a photogrammetric method for measuring the shape profile and internal volume of PAMs. A test setup, method of image data acquisition, and a preliminary analysis of the image data, is presented in this research. A 22.2 mm (7/8 in) diameter PAM is used to demonstrate the photogrammetric procedure and test its accuracy. Analysis of the tested PAM characterizes trends of the shape profile with respect to pressure and contraction. The common method of estimating the diameter—through the use of the cylindrical approximation and initial geometry of the PAM—is tested by comparison to the measured shape profile data. Finally, a simple method of calculating the internal volume using the measured shape profile data is developed. The presented method of acquiring photogrammetric measurements of PAM shape produces an accurate characterization of its shape profile, thereby mitigating uncertainty in PAM shape in analysis and other efforts. Full article

(This article belongs to the Special Issue Pneumatic Soft Actuators)

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25 pages, 3066 KiB

Open AccessArticle

Characterization and Analysis of Extensile Fluidic Artificial Muscles

by Jacek Garbulinski, Sai C. Balasankula and Norman M. Wereley

Actuators 2021, 10(2), 26; https://0-doi-org.brum.beds.ac.uk/10.3390/act10020026 - 30 Jan 2021

Cited by 10 | Viewed by 4871

Abstract

Extensile fluidic artificial muscles (EFAMs) are soft actuators known for their large ranges of extension, low weight, and blocked forces comparable to those of pneumatic cylinders. EFAMs have yet to be studied in a way that thoroughly focuses on their manufacturing, experimental characterization, [...] Read more.

Extensile fluidic artificial muscles (EFAMs) are soft actuators known for their large ranges of extension, low weight, and blocked forces comparable to those of pneumatic cylinders. EFAMs have yet to be studied in a way that thoroughly focuses on their manufacturing, experimental characterization, and modeling. A fabrication method was developed for production of two EFAMs. The quasi-static axial force response of EFAMs to varying displacement was measured by testing two specimens under isobaric conditions over a pressure range of 103.4–517.1 kPa (15–75 psi) with

103.4

kPa (15 psi) increments. The muscles were characterized by a blocked force of 280 N and a maximum stroke of 98% at

517.1

kPa (75 psi). A force-balance model was used to analyze EFAM response. Prior work employing the force-balance approach used hyper-elastic constitutive models based on polynomial expressions. In this study, these models are validated for EFAMs, and new constitutive models are proposed that better represent the measured stress values of rubber as a function of strain. These constitutive models are compared in terms of accuracy when estimating pressure-dependent stress–strain relationships of the bladder material. The analysis demonstrates that the new hyper-elastic stress models have an error 5% smaller than models previously employed for EFAMs for the same number of coefficients. Finally, the analysis suggests that the new stress functions have smaller errors than the polynomial stress model with the same number of coefficients, guarantee material stability, and are more conservative about the stress values for strains outside of the testing range. Full article

(This article belongs to the Special Issue Pneumatic Soft Actuators)

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13 pages, 3468 KiB

Open AccessArticle

A Novel Computer-Controlled Maskless Fabrication Process for Pneumatic Soft Actuators

by Luke J. Tinsley and Russell A. Harris

Actuators 2020, 9(4), 136; https://0-doi-org.brum.beds.ac.uk/10.3390/act9040136 - 11 Dec 2020

Cited by 4 | Viewed by 3738

Abstract

Template-based and additive manufacturing techniques have demonstrated some fabrication routes for creating pneumatic soft actuators. However, as the complexity and capability of the actuators continue to develop, the limitations of these approaches are becoming evident. These include difficulties for design variations, process speed [...] Read more.

Template-based and additive manufacturing techniques have demonstrated some fabrication routes for creating pneumatic soft actuators. However, as the complexity and capability of the actuators continue to develop, the limitations of these approaches are becoming evident. These include difficulties for design variations, process speed and resolution, material compatibility and scalability, which hinder and restrict both the possible capabilities of the technology and its transition from research to industry. This body of work presents a computer-controlled, maskless manufacturing process with a different approach to allow for high-speed, low-cost and flexible creation of pneumatic soft actuation networks comprising multi-material construction. This was investigated through a bespoke fabrication platform that provides computer-controlled localised plasma treatment to selectively modify the chemical behaviour on the surface of silicone and polyethylene terephthalate (PET) bodies. The altered surface chemistry facilitated selective bond formation between the treated parts of the surface and, consequently, greater design variation and control over the pneumatic chambers that were formed. Selective treatment patterns allowed nonlinear pneumatic chamber designs to be created, and the strength of bonded silicone structures was shown to facilitate large deformations in the actuators. Furthermore, the different interactions between the plasma and silicone were leveraged to achieve feature sizes of <1 mm and treatment speeds of 20 mm² per second of exposure. Two multi-material pneumatic soft actuators were then fabricated to demonstrate the potential of the platform as an automated manufacturing route for soft actuators. Full article

(This article belongs to the Special Issue Pneumatic Soft Actuators)

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18 pages, 4215 KiB

Open AccessArticle

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

by Yinglong Chen, Junhao Zhang and Yongjun Gong

Actuators 2020, 9(4), 107; https://0-doi-org.brum.beds.ac.uk/10.3390/act9040107 - 21 Oct 2020

Cited by 11 | Viewed by 6527

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Pneumatic Soft Actuators)

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14 pages, 5046 KiB

Open AccessArticle

Experimental Research on the Hysteretic Behaviour of Pressurized Artificial Muscles Made from Elastomers with Aramid Fibre Insertions

by Ovidiu Filip, Andrea Deaconescu and Tudor Deaconescu

Actuators 2020, 9(3), 83; https://0-doi-org.brum.beds.ac.uk/10.3390/act9030083 - 11 Sep 2020

Cited by 2 | Viewed by 3294

Abstract

Inherent hysteresis behaviour of pressurized artificial muscles is complicated to understand and handle, calling for experimental research that allows the modelling of this phenomenon. The paper presents the results of the experimental study of the hysteretic behaviour of a small-size pneumatic muscle. The [...] Read more.

Inherent hysteresis behaviour of pressurized artificial muscles is complicated to understand and handle, calling for experimental research that allows the modelling of this phenomenon. The paper presents the results of the experimental study of the hysteretic behaviour of a small-size pneumatic muscle. The specific hysteresis loops were revealed by isotonic and isometric tests. Starting from hypothesis according to that the tube used for the pneumatic muscle is made entirely of aramid fibres enveloped by an elastomer material that merely ensures their airtightness, the paper presents the hysteresis curves that describe the radial and axial dimensional modifications as well as the variation of the developed forces for different feed pressures. The obtained third-degree polynomial equations underlie the configuration of high-performance positioning systems. Full article

(This article belongs to the Special Issue Pneumatic Soft Actuators)

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17 pages, 7104 KiB

Open AccessEditor’s ChoiceArticle

Self-Healing and High Interfacial Strength in Multi-Material Soft Pneumatic Robots via Reversible Diels–Alder Bonds

by Seppe Terryn, Ellen Roels, Joost Brancart, Guy Van Assche and Bram Vanderborght

Actuators 2020, 9(2), 34; https://0-doi-org.brum.beds.ac.uk/10.3390/act9020034 - 30 Apr 2020

Cited by 37 | Viewed by 7777

Abstract

In new-generation soft robots, the actuation performance can be increased by using multiple materials in the actuator designs. However, the lifetime of these actuators is often limited due to failure that occurs at the weak multi-material interfaces that rely almost entirely on physical [...] Read more.

In new-generation soft robots, the actuation performance can be increased by using multiple materials in the actuator designs. However, the lifetime of these actuators is often limited due to failure that occurs at the weak multi-material interfaces that rely almost entirely on physical interactions and where stress concentration appears during actuation. This paper proposes to develop soft pneumatic actuators out of multiple Diels–Alder polymers that can generate strong covalent bonds at the multi-material interface by means of a heat–cool cycle. Through tensile testing it is proven that high interfacial strength can be obtained between two merged Diels–Alder polymers. This merging principle is exploited in the manufacturing of multi-material bending soft pneumatic actuators in which interfaces are no longer the weakest links. The applicability of the actuators is illustrated by their operation in a soft hand and a soft gripper demonstrator. In addition, the use of Diels–Alder polymers incorporates healability in bending actuators. It is experimentally illustrated that full recovery of severe damage can be obtained by subjecting the multi-material actuators to a healing cycle. Full article

(This article belongs to the Special Issue Pneumatic Soft Actuators)

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17 pages, 5495 KiB

Open AccessArticle

The Design, Kinematics and Torque Analysis of the Self-Bending Soft Contraction Actuator

by Alaa Al-Ibadi, Samia Nefti-Meziani and Steve Davis

Actuators 2020, 9(2), 33; https://0-doi-org.brum.beds.ac.uk/10.3390/act9020033 - 29 Apr 2020

Cited by 9 | Viewed by 5358

Abstract

This article presents the development of a self-bending contraction actuator (SBCA) through the analysis of its structure, kinematics, and torque formulas, and then explores its applications. The proposed actuator has been fabricated by two methods to prove the efficiency of the human body [...] Read more.

This article presents the development of a self-bending contraction actuator (SBCA) through the analysis of its structure, kinematics, and torque formulas, and then explores its applications. The proposed actuator has been fabricated by two methods to prove the efficiency of the human body inspiration, which represents the covering of human bones by soft tissues to protect the bone and give the soft texture. The SBCA provides bending behaviour along with a high force-to-weight ratio. As with the simple pneumatic muscle actuator (PMA), the SBCA is soft and easy to implement. Both the kinematics and the torque formula presented for the SBCA are scalable and can be used with different actuator sizes. The bending actuator has been tested under an air pressure of up to 500 kPa, and the behaviour of its bending angle, parameters, dimensions, and the bending torques have been illustrated. On the other hand, the experiments showed the efficient performances of the actuator and validate the proposed kinematics. Therefore, the actuator can be used in many different applications, such as soft grippers and continuum arms. Full article

(This article belongs to the Special Issue Pneumatic Soft Actuators)

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13 pages, 3897 KiB

Open AccessArticle

A Crawling Soft Robot Driven by Pneumatic Foldable Actuators Based on Miura-Ori

by Meng Yu, Weimin Yang, Yuan Yu, Xiang Cheng and Zhiwei Jiao

Actuators 2020, 9(2), 26; https://0-doi-org.brum.beds.ac.uk/10.3390/act9020026 - 09 Apr 2020

Cited by 35 | Viewed by 9884

Abstract

Origami structures are highly demanded for engineering applications. Using origami folding to design and actuate mechanisms and machines offers attractive opportunities. In this paper, we design a crawling robot driven by pneumatic foldable actuators (PFAs) based on Miura-ori, according to the parallel foldable [...] Read more.

Origami structures are highly demanded for engineering applications. Using origami folding to design and actuate mechanisms and machines offers attractive opportunities. In this paper, we design a crawling robot driven by pneumatic foldable actuators (PFAs) based on Miura-ori, according to the parallel foldable structure and different control patterns, which can perform different movements. The PFA inspired from Miura-ori is composed of a folding part, transition part, and sealing part, made by flexible materials and a paper skeleton. This actuator can obtain a large deformation by folding under negative pressure due to its own characteristics, and the relationship between deformation and pressure is analyzed. According to the different folding and unfolding times of left and right actuators, the crawling robot can perform both linear and turning movements. The speed of the robot is about 5 mm/s and it can turn at a speed of about 15°/s. The crawling robot uses the ability of the foldable structure to cope with the challenges of different environments and tasks. Full article

(This article belongs to the Special Issue Pneumatic Soft Actuators)

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Review

Jump to: Research, Other

26 pages, 14023 KiB

Open AccessReview

Soft Robotics: A Review of Recent Developments of Pneumatic Soft Actuators

by James Walker, Thomas Zidek, Cory Harbel, Sanghyun Yoon, F. Sterling Strickland, Srinivas Kumar and Minchul Shin

Actuators 2020, 9(1), 3; https://0-doi-org.brum.beds.ac.uk/10.3390/act9010003 - 10 Jan 2020

Cited by 193 | Viewed by 30785

Abstract

This paper focuses on the recent development of soft pneumatic actuators for soft robotics over the past few years, concentrating on the following four categories: control systems, material and construction, modeling, and sensors. This review work seeks to provide an accelerated entrance to [...] Read more.

This paper focuses on the recent development of soft pneumatic actuators for soft robotics over the past few years, concentrating on the following four categories: control systems, material and construction, modeling, and sensors. This review work seeks to provide an accelerated entrance to new researchers in the field to encourage research and innovation. Advances in methods to accurately model soft robotic actuators have been researched, optimizing and making numerous soft robotic designs applicable to medical, manufacturing, and electronics applications. Multi-material 3D printed and fiber optic soft pneumatic actuators have been developed, which will allow for more accurate positioning and tactile feedback for soft robotic systems. Also, a variety of research teams have made improvements to soft robot control systems to utilize soft pneumatic actuators to allow for operations to move more effectively. This review work provides an accessible repository of recent information and comparisons between similar works. Future issues facing soft robotic actuators include portable and flexible power supplies, circuit boards, and drive components. Full article

(This article belongs to the Special Issue Pneumatic Soft Actuators)

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Other

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11 pages, 3162 KiB

Open AccessPerspective

Recycling-Oriented Design in Soft Robotics

by Anh Minh Nguyen and Arthur Seibel

Actuators 2019, 8(3), 62; https://0-doi-org.brum.beds.ac.uk/10.3390/act8030062 - 12 Aug 2019

Cited by 7 | Viewed by 6784

Abstract

Soft robotics is a novel approach in the field of robotics. Soft robots or soft actuators are typically polymer-based and are characterized by their flexibility and adaptability, which brings new far-reaching applications. Soft robotics is currently at the peak of its research. One [...] Read more.

Soft robotics is a novel approach in the field of robotics. Soft robots or soft actuators are typically polymer-based and are characterized by their flexibility and adaptability, which brings new far-reaching applications. Soft robotics is currently at the peak of its research. One circumstance that is also present in this age is constant climate change; there is a demand for sustainability. This goes hand in hand with the design of products that are suitable for recycling. Today, more is expected of an engineer than just function-oriented design. This article looks at soft robotics from the point of view of sustainability. Since nature operates in cycles, the aim is to design products in such a way that they can be introduced into cycles. Three recycling cycles for products can be distinguished, which take place during production, during product use, and after product life. Within the framework of this work, special design measures are reviewed for fluidic elastomer actuators—a characteristic type of soft actuators—so that they can be integrated into the recycling process. Full article

(This article belongs to the Special Issue Pneumatic Soft Actuators)

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