Special Issue "Feature Papers"

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A special issue of Actuators (ISSN 2076-0825).

Deadline for manuscript submissions: closed (15 October 2015)

Special Issue Editor

Guest Editor
Prof. Dr. Delbert Tesar (Website)

Robotics Research Group, The University of Texas at Austin, 1 University Station, R9925, Austin, TX 78712, USA
Phone: +1 512 471 3039
Interests: robotics, electro-mechanical actuators, embedded intelligence; open architecture vehicles, ships, aircraft, machinery for manufacturing; human rehabilitation systems; long duration lunar base habitat operation

Special Issue Information

Dear Colleagues,

We plan to publish a Special Issue on "Feature Papers" in order to give a broad overview of our area. We are looking for top quality papers which will be published free of charge in Open Access form. Authors will be the editorial board members and researchers invited by the editorial office and the Editor-in-Chief. Papers could be both long research papers and papers describing the current state of the art in one of the areas covered by the journal.

Prof. Dr. Delbert Tesar
Guest Editor

Submission

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Actuators is an international peer-reviewed Open Access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 300 CHF (Swiss Francs). English correction and/or formatting fees of 250 CHF (Swiss Francs) will be charged in certain cases for those articles accepted for publication that require extensive additional formatting and/or English corrections.


Keywords

  • actuator applications
  • survey of suppliers
  • survey of research programs
  • standardization
  • domain-specific minimum sets
  • certification
  • actuator architecture
  • internal sensors
  • prime movers
  • gear reducers
  • actuator intelligence
  • electronic controllers/power supplies
  • actuator design process
  • recommended manufacture
  • actuator forecasts

Published Papers (10 papers)

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Research

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Open AccessArticle The UC Softhand: Light Weight Adaptive Bionic Hand with a Compact Twisted String Actuation System
Actuators 2016, 5(1), 1; doi:10.3390/act5010001
Received: 20 October 2015 / Revised: 14 December 2015 / Accepted: 17 December 2015 / Published: 23 December 2015
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Abstract
In this paper, we present the design and development of the UC-Softhand. The UC Softhand is a low cost, Bionic and adaptive hand that takes advantage of compliant joints. By optimization of the actuation strategy as well as the actuation mechanism, we [...] Read more.
In this paper, we present the design and development of the UC-Softhand. The UC Softhand is a low cost, Bionic and adaptive hand that takes advantage of compliant joints. By optimization of the actuation strategy as well as the actuation mechanism, we could develop an anthropomorphic hand that embeds three actuators, transmission mechanisms, controllers and drivers in the palm of the hand, and weighs only 280 g, making it one of the lightest bionic hands that has been created so far. The key aspect of the UC Softhand is utilization of a novel compact twisted string actuation mechanism, that allows a considerable weight and cost reduction compared to its predecessor. Full article
(This article belongs to the Special Issue Feature Papers)
Figures

Open AccessArticle What Is an Artificial Muscle? A Systemic Approach.
Actuators 2015, 4(4), 336-352; doi:10.3390/act4040336
Received: 24 October 2015 / Revised: 28 November 2015 / Accepted: 9 December 2015 / Published: 11 December 2015
Cited by 1 | PDF Full-text (696 KB) | HTML Full-text | XML Full-text
Abstract
Artificial muscles define a large category of actuators we propose to analyze in a systemic framework by considering any artificial muscle as an open-loop stable system for any output which represents an artificial muscle dimension resulting from its “contraction”, understood in a [...] Read more.
Artificial muscles define a large category of actuators we propose to analyze in a systemic framework by considering any artificial muscle as an open-loop stable system for any output which represents an artificial muscle dimension resulting from its “contraction”, understood in a broad meaning. This approach makes it possible to distinguish the artificial muscle from other actuators and to specify an original model for a linear artificial muscle, according to the theory of linear systems. Such a linear artificial muscle concept exhibits a constant stiffness independent on its control value. It is shown that a biomimetic actuator, made of two antagonist artificial muscles, requires that artificial muscle static characteristic, even in its most simplified form, is non-linear in the meaning of systems theory, to make possible the control of both actuator position and stiffness. However, we also attempt to show that a linear viscous damping can be a practical way for the dynamic behavior of the artificial muscle to be in relatively good accordance with the so-called Hill curve, interpreted as the dynamic characteristic linking the maximum contraction velocity of the artificial muscle to varying loads lifted against gravity. Full article
(This article belongs to the Special Issue Feature Papers)
Open AccessArticle Hybrid Multi-Physics Modeling of an Ultra-Fast Electro-Mechanical Actuator
Actuators 2015, 4(4), 314-335; doi:10.3390/act4040314
Received: 29 September 2015 / Revised: 20 November 2015 / Accepted: 24 November 2015 / Published: 8 December 2015
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Abstract
The challenges of an HVDC breaker are to generate impulsive forces in the order of hundreds of kilonewtons within fractions of a millisecond, to withstand the arising internal mechanical stresses and to transmit these forces via an electrically-insulating device to the contact [...] Read more.
The challenges of an HVDC breaker are to generate impulsive forces in the order of hundreds of kilonewtons within fractions of a millisecond, to withstand the arising internal mechanical stresses and to transmit these forces via an electrically-insulating device to the contact system with minimum time delay. In this work, several models were developed with different levels of complexity, computation time and accuracy. Experiments were done with two mushroom-shaped armatures to validate the developed simulation models. It was concluded that although the electromagnetic force generation mechanism is highly sensitive to the mechanical response of the system, the developed first order hybrid model is able to predict the performance of the breaker with good accuracy. Full article
(This article belongs to the Special Issue Feature Papers)
Open AccessArticle Elastic Cube Actuator with Six Degrees of Freedom Output
Actuators 2015, 4(3), 203-216; doi:10.3390/act4030203
Received: 8 July 2015 / Revised: 20 August 2015 / Accepted: 26 August 2015 / Published: 7 September 2015
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Abstract
Unlike conventional rigid actuators, soft robotic technologies possess inherent compliance, so they can stretch and twist along every axis without the need for articulated joints. This compliance is exploited here using dielectric elastomer membranes to develop a novel six degrees of freedom [...] Read more.
Unlike conventional rigid actuators, soft robotic technologies possess inherent compliance, so they can stretch and twist along every axis without the need for articulated joints. This compliance is exploited here using dielectric elastomer membranes to develop a novel six degrees of freedom (6-DOF) polymer actuator that unifies ordinarily separate components into a simple cubic structure. This cube actuator design incorporates elastic dielectric elastomer membranes on four faces which are coupled by a cross-shaped end effector. The inherent elasticity of each membrane greatly reduces kinematic constraint and enables a 6-DOF actuation output to be produced via the end effector. An electro-mechanical model of the cube actuator is presented that captures the non-linear hyperelastic behaviour of the active membranes. It is demonstrated that the model accurately predicts actuator displacement and blocking moment for a range of input voltages. Experimental testing of a prototype 60 mm device demonstrates 6-DOF operation. The prototype produces maximum linear and rotational displacements of ±2.6 mm (±4.3%) and ±4.8° respectively and a maximum blocking moment of ±76 mNm. The capacity for full 6-DOF actuation from a compact, readily scalable and easily fabricated polymeric package enables implementation in a range of mechatronics and robotics applications. Full article
(This article belongs to the Special Issue Feature Papers)
Open AccessArticle Design, Manufacturing and Test of a High Lift Secondary Flight Control Surface with Shape Memory Alloy Post-Buckled Precompressed Actuators
Actuators 2015, 4(3), 156-171; doi:10.3390/act4030156
Received: 8 October 2014 / Revised: 1 July 2015 / Accepted: 8 July 2015 / Published: 28 July 2015
Cited by 1 | PDF Full-text (816 KB) | HTML Full-text | XML Full-text
Abstract
The use of morphing components on aerospace structures can greatly increase the versatility of an aircraft. This paper presents the design, manufacturing and testing of a new kind of adaptive airfoil with actuation through Shape Memory Alloys (SMA). The developed adaptive flap [...] Read more.
The use of morphing components on aerospace structures can greatly increase the versatility of an aircraft. This paper presents the design, manufacturing and testing of a new kind of adaptive airfoil with actuation through Shape Memory Alloys (SMA). The developed adaptive flap system makes use of a novel actuator that employs SMA wires in an antagonistic arrangement with a Post-Buckled Precompressed (PBP) mechanism. SMA actuators are usually used in an antagonistic arrangement or are arranged to move structural components with linearly varying resistance levels similar to springs. Unfortunately, most of this strain energy is spent doing work on the passive structure rather than performing the task at hand, like moving a flight control surface or resisting air loads. A solution is the use of Post-Buckled Precompressed (PBP) actuators that are arranged so that the active elements do not waste energy fighting passive structural stiffnesses. One major problem with PBP actuators is that the low tensile strength of the piezoelectric elements can often result in tensile failure of the actuator on the convex face. A solution to this problem is the use of SMA as actuator material due to their tolerance of tensile stresses. The power consumption to hold deflections is reduced by approximately 20% with the Post-Buckled Precompressed mechanism. Conventional SMAs are essentially non-starters for many classes of aircraft due to the requirement of holding the flight control surfaces in a given position for extremely long times to trim the vehicle. For the reason that PBP actuators balance out air and structural loads, the steady-state load on the SMAs is essentially negligible, when properly designed. Simulations and experiments showed that the SMAPBP actuator shows tip rotations on the order of 45°, which is nearly triple the levels achieved by piezoelectric PBP actuators. The developed SMAPBP actuator was integrated in a NACA0012 airfoil with a flexible skin to carry out wind tunnel tests. Full article
(This article belongs to the Special Issue Feature Papers)
Open AccessArticle Characterization and Testing of an Electrorheological Fluid Valve for Control of ERF Actuators
Actuators 2015, 4(3), 135-155; doi:10.3390/act4030135
Received: 24 April 2015 / Revised: 15 June 2015 / Accepted: 23 June 2015 / Published: 26 June 2015
Cited by 1 | PDF Full-text (2141 KB) | HTML Full-text | XML Full-text
Abstract
Previous studies of electrorheological fluids (ERFs) were motivated by brake, clutch, damping, haptic and resistive applications, but never motivated towards developing an ERF based-hydraulic rotary actuator. One design to make such an actuator is to use ERF-based valves. To fully understand the [...] Read more.
Previous studies of electrorheological fluids (ERFs) were motivated by brake, clutch, damping, haptic and resistive applications, but never motivated towards developing an ERF based-hydraulic rotary actuator. One design to make such an actuator is to use ERF-based valves. To fully understand the performance of such an actuator, it is imperative to study ERF valves. For this reason, this paper presents a summary of design considerations for creating ERF-based actuators, an ERF-based valve design for an ERF actuator and a new experimental test-bed to obtain viscosity and yield characteristics of the ERF at flow rates as low as 0.049 L/min, an order of magnitude lower than industrial rheometers. The new test-bed successfully measured the dynamic viscosity of the ERF to be at 0.6 Pa-s for low flow rates and 0.2 Pa-s for higher flow rates. The presented valve design can successfully resist 1 MPa of fluid pressure, which is an operation mode higher than any haptic and damping applications in the literature. The experiments also shows that higher flow rates negatively affect the ERF’s yield characteristics for the first time in a situation where the ERF valve completely blocks flow. When the flow rates are increased, the response time to a fully-closed valve increases, the effective yield capability of the ERF decreases and the conductivity of the ERF increases. Full article
(This article belongs to the Special Issue Feature Papers)
Figures

Open AccessArticle Ultrasonic Transducer Fabricated Using Lead-Free BFO-BTO+Mn Piezoelectric 1-3 Composite
Actuators 2015, 4(2), 127-134; doi:10.3390/act4020127
Received: 1 April 2015 / Revised: 12 May 2015 / Accepted: 27 May 2015 / Published: 29 May 2015
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Abstract
Mn-doped 0.7BiFeO3-0.3BaTiO3 (BFO-0.3BTO+Mn 1% mol) lead-free piezoelectric ceramic were fabricated by traditional solid state reaction. The phase structure, microstructure, and ferroelectric properties were investigated. Additionally, lead-free 1–3 composites with 60% volume fraction of BFO-BTO+Mn ceramic were fabricated for ultrasonic [...] Read more.
Mn-doped 0.7BiFeO3-0.3BaTiO3 (BFO-0.3BTO+Mn 1% mol) lead-free piezoelectric ceramic were fabricated by traditional solid state reaction. The phase structure, microstructure, and ferroelectric properties were investigated. Additionally, lead-free 1–3 composites with 60% volume fraction of BFO-BTO+Mn ceramic were fabricated for ultrasonic transducer applications by a conventional dice-and-fill method. The BFO-BTO+Mn 1-3 composite has a higher electromechanical coupling coefficient (kt = 46.4%) and lower acoustic impedance (Za ~ 18 MRayls) compared with that of the ceramic. Based on this, lead-free piezoelectric ceramic composite, single element ultrasonic transducer with a center frequency of 2.54 MHz has been fabricated and characterized. The single element transducer exhibits good performance with a broad bandwidth of 53%. The insertion loss of the transducer was about 33.5 dB. Full article
(This article belongs to the Special Issue Feature Papers)
Open AccessArticle A Compact Ionic Polymer Metal Composite (IPMC) System with Inductive Sensor for Closed Loop Feedback
Actuators 2015, 4(2), 114-126; doi:10.3390/act4020114
Received: 13 March 2015 / Revised: 13 May 2015 / Accepted: 14 May 2015 / Published: 19 May 2015
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Abstract
Ionic polymer metal composite (IPMC), of which a low actuating voltage (<5 V), high power efficiency and biocompatibility makes it a proven candidate for low power devices. However, due to its inherent nonlinear behaviour and time-variance, feedback control, as well as reliable [...] Read more.
Ionic polymer metal composite (IPMC), of which a low actuating voltage (<5 V), high power efficiency and biocompatibility makes it a proven candidate for low power devices. However, due to its inherent nonlinear behaviour and time-variance, feedback control, as well as reliable sensing means, are required for accurate operations. This paper presents an IPMC actuator implemented with an inductive sensor to enhance the reliability and compactness of the overall device. A practical, low cost and importantly, compact inductive sensor fabricated on a printed circuit board (PCB) is proposed here. Target material selections and coil design considerations are discussed. It is experimentally determined that the inductive sensor has comparable performance to a laser sensor. Based on a proportional-integral-derivative (PID) control results the inductive sensor has demonstrated to be an alternative to a laser sensor allowing devices using IPMC actuators to be compact. Full article
(This article belongs to the Special Issue Feature Papers)
Open AccessArticle Ferroelectric KNNT Fibers by Thermoplastic Extrusion Process: Microstructure and Electromechanical Characterization
Actuators 2015, 4(2), 99-113; doi:10.3390/act4020099
Received: 20 March 2015 / Revised: 30 April 2015 / Accepted: 5 May 2015 / Published: 8 May 2015
Cited by 2 | PDF Full-text (699 KB) | HTML Full-text | XML Full-text
Abstract
B-site substitution in KNN with tantalum results in a higher d33 and dielectric constant. This higher value makes KNNT interesting for lead-free actuator applications. KNNT fibers with diameters of 300 and 500 μm have been extruded and sintered at 1200 °C [...] Read more.
B-site substitution in KNN with tantalum results in a higher d33 and dielectric constant. This higher value makes KNNT interesting for lead-free actuator applications. KNNT fibers with diameters of 300 and 500 μm have been extruded and sintered at 1200 °C in a KNNT-enriched atmosphere. Subsequently, the influence of fiber diameter on the microstructure (porosity and grain size) was investigated. The measurements revealed that with decreasing fiber diameter, the porosity increases, whereas the grain size decreases. The influence of these microstructural differences on the piezoelectric properties was evaluated using a novel characterization procedure for single fibers. The larger diameter fibers show an increase in the electromechanical properties measured, i.e., d33, tanδ, Pr, Ec and the free longitudinal fiber displacement, when compared to smaller diameter fibers. The lower alkali losses result in a larger grain size, a higher density during sintering and lead to higher electromechanical properties. Full article
(This article belongs to the Special Issue Feature Papers)

Review

Jump to: Research

Open AccessReview Self-Sensing Ionic Polymer Actuators: A Review
Actuators 2015, 4(1), 17-38; doi:10.3390/act4010017
Received: 26 December 2014 / Revised: 19 January 2015 / Accepted: 17 February 2015 / Published: 2 March 2015
Cited by 8 | PDF Full-text (987 KB) | HTML Full-text | XML Full-text
Abstract
Ionic electromechanically active polymers (IEAP) are laminar composites that can be considered attractive candidates for soft actuators. Their outstanding properties such as low operating voltage, easy miniaturization, and noiseless operation are, however, marred by issues related to the repeatability in the production [...] Read more.
Ionic electromechanically active polymers (IEAP) are laminar composites that can be considered attractive candidates for soft actuators. Their outstanding properties such as low operating voltage, easy miniaturization, and noiseless operation are, however, marred by issues related to the repeatability in the production and operation of these materials. Implementing closed-loop control for IEAP actuators is a viable option for overcoming these issues. Since IEAP laminates also behave as mechanoelectrical sensors, it is advantageous to combine the actuating and sensing functionalities of a single device to create a so-called self-sensing actuator. This review article systematizes the state of the art in producing self-sensing ionic polymer actuators. The IEAPs discussed in this paper are conducting (or conjugated) polymers actuators (CPA), ionic polymer-metal composite (IPMC), and carbonaceous polymer laminates. Full article
(This article belongs to the Special Issue Feature Papers)

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