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13 pages, 5636 KiB

Open AccessArticle

Fabrication of a Polyimide Film Pneumatic Actuator by Molding and Welding Processes

by Daisuke Yamaguchi, Tatsuya Hanaki, Yuji Ishino, Masaya Takasaki and Takeshi Mizuno

Actuators 2021, 10(8), 177; https://doi.org/10.3390/act10080177 - 30 Jul 2021

Cited by 3 | Viewed by 2604

Abstract

The bellows pneumatic actuator, which is made by folding a non-stretch film, has been proposed for various applications because it is easy to fabricate and is extremely thin and light. However, it has subpar durability performance, especially in the folded part of the film. In this study, we propose an actuator with a pod structure that possesses high design flexibility and is free from folding. A method of molding a pod structure on a polyimide film was established and a pneumatic actuator was successfully fabricated by using PI films. Two types of PI film pneumatic actuators with the same curvature, bellows type, and pod type were fabricated. Both were confirmed to have equivalent output characteristics. The bending angle and generated torque of the pod-structure actuator were 34° and 3.3 mNm, respectively. In addition, the pod structure has approximately twice the durability of the bellows structure. By using the fabrication method proposed in this paper, it is possible to realize an air chamber (i.e., an actuator) that has both high durability and bending motion. Full article

(This article belongs to the Special Issue Artificial Muscles and Soft Actuation)

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24 pages, 6930 KiB

Open AccessArticle

Modeling of Resistive Forces and Buckling Behavior in Variable Recruitment Fluidic Artificial Muscle Bundles

by Jeong Yong Kim, Nicholas Mazzoleni and Matthew Bryant

Actuators 2021, 10(3), 42; https://doi.org/10.3390/act10030042 - 26 Feb 2021

Cited by 13 | Viewed by 3200

Abstract

Fluidic artificial muscles (FAMs), also known as McKibben actuators, are a class of fiber-reinforced soft actuators that can be pneumatically or hydraulically pressurized to produce muscle-like contraction and force generation. When multiple FAMs are bundled together in parallel and selectively pressurized, they can act as a multi-chambered actuator with bioinspired variable recruitment capability. The variable recruitment bundle consists of motor units (MUs)—groups of one of more FAMs—that are independently pressurized depending on the force demand, similar to how groups of muscle fibers are sequentially recruited in biological muscles. As the active FAMs contract, the inactive/low-pressure units are compressed, causing them to buckle outward, which increases the spatial envelope of the actuator. Additionally, a FAM compressed past its individual free strain applies a force that opposes the overall force output of active FAMs. In this paper, we propose a model to quantify this resistive force observed in inactive and low-pressure FAMs and study its implications on the performance of a variable recruitment bundle. The resistive force behavior is divided into post-buckling and post-collapse regions and a piecewise model is devised. An empirically-based correction method is proposed to improve the model to fit experimental data. Analysis of a bundle with resistive effects reveals a phenomenon, unique to variable recruitment bundles, defined as free strain gradient reversal. Full article

(This article belongs to the Special Issue Artificial Muscles and Soft Actuation)

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19 pages, 7219 KiB

Open AccessArticle

Position Control of the Dielectric Elastomer Actuator Based on Fractional Derivatives in Modelling and Control

by Timi Karner and Janez Gotlih

Actuators 2021, 10(1), 18; https://doi.org/10.3390/act10010018 - 19 Jan 2021

Cited by 6 | Viewed by 3134

Abstract

Successful control of a dielectric elastomer actuator (DEA) can be a challenging task, especially if no overshoot is desired. The work presents the first use of the

P I^{λ} D^{μ}

control for a dielectric elastomer actuator to eliminate the overshoot. The [...] Read more.

Successful control of a dielectric elastomer actuator (DEA) can be a challenging task, especially if no overshoot is desired. The work presents the first use of the

P I^{λ} D^{μ}

control for a dielectric elastomer actuator to eliminate the overshoot. The mathematical model of the dielectric elastomer was established using the fractional Kelvin-Voigt model. Step responses are first tested in the Laplace domain, which gave the most satisfactory results. However, they did not represent the real model. It cannot have negative force acting on the dielectric elastomer actuator. Simulations in Matlab/Simulink were performed to obtain more realistic responses, where output of the

P I^{λ} D^{μ}

controller was limited. Initial parameters for a PID control were obtained by the Wang–Juang–Chan algorithm for the first order plus death time function approximation to the step response of the model, and reused as the basis for the

P I^{λ} D^{μ}

actuator control. A quasi-anti-windup method was introduced to the final control algorithm. Step responses of the PID and the

P I^{λ} D^{μ}

in different domains were verified by simulation and validated by experiments. Experiments proved that the fractional calculus

P I^{λ} D^{μ}

step responses exceeded performance of the basic PID controller for DEA in terms of response time, settling time, and overshoot elimination. Full article

(This article belongs to the Special Issue Artificial Muscles and Soft Actuation)

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