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Actuators, Volume 7, Issue 3 (September 2018)

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Open AccessEditorial Pneumatic Actuators
Actuators 2018, 7(3), 62; https://doi.org/10.3390/act7030062
Received: 5 September 2018 / Accepted: 12 September 2018 / Published: 13 September 2018
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(This article belongs to the Special Issue Pneumatic Actuators)
Open AccessArticle High-Bending-Stiffness Connector (HBSC) and High-Authority Piezoelectric Actuator (HAPA) Made of Such
Actuators 2018, 7(3), 61; https://doi.org/10.3390/act7030061
Received: 30 July 2018 / Revised: 10 September 2018 / Accepted: 10 September 2018 / Published: 12 September 2018
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Abstract
High-authority piezoelectric actuator (HAPA) is a term used to describe high-performance piezoelectric actuators of relatively large displacement (≥50 μm) and high blocking force (≥100 N), but compact in size. One such piezoelectric actuator is described in this paper, which is made possible by
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High-authority piezoelectric actuator (HAPA) is a term used to describe high-performance piezoelectric actuators of relatively large displacement (≥50 μm) and high blocking force (≥100 N), but compact in size. One such piezoelectric actuator is described in this paper, which is made possible by means of high-bending-stiffness connector (HBSC) that connects multiple commercial piezoceramic stacks into a stable 2- (or multi-) level actuation configuration. Key design requirements for the HBSC are described. Computer simulation results and experimental verification are presented. A HAPA-(2 + 2) actuator was fabricated from such a HBSC, in which there are two commercial PZT stacks projecting upwards in the upper level and two projecting downwards in the lower lever, all of 5 × 5 mm2 in cross-section and 40 mm in length. The HAPA-(2 + 2) actuator prototype displays about twice the overall stroke and blocking force of individual stacks, being about 90 μm and >1600 N, respectively. This compares favorably with lever-arm, flextensional, and telescopic actuators, of which the blocking force is adversely affected. Using a similar concept, HBSCs and HAPAs of other designs are presented. In addition to being stand-alone actuators, the HAPAs can be used as the active material to drive existing displacement amplification schemes to produce piezoelectric actuators of exceptional performance characteristics. Full article
(This article belongs to the Special Issue Piezoelectric Actuators 2018)
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Open AccessArticle Hi-Fi Stake Piezo Single Crystal Actuator
Actuators 2018, 7(3), 60; https://doi.org/10.3390/act7030060
Received: 30 July 2018 / Revised: 23 August 2018 / Accepted: 27 August 2018 / Published: 12 September 2018
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Abstract
High fidelity (Hi-Fi) piezoelectric single crystal stake actuators are presented in this work. They are made of multiple rectangular d32 mode lead-based relaxor ferroelectric (notably Pb(Zn1/3Nb2/3)O3-PbTiO3 (PZN-PT) and Pb(In0.5Nb0.5)O3-Pb(Mg
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High fidelity (Hi-Fi) piezoelectric single crystal stake actuators are presented in this work. They are made of multiple rectangular d32 mode lead-based relaxor ferroelectric (notably Pb(Zn1/3Nb2/3)O3-PbTiO3 (PZN-PT) and Pb(In0.5Nb0.5)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT)) single crystals bonded along their long edges with the aid of compliant polymeric edge guides into a square or polygonal pipe-like construction. Due to the highly stable engineered domain structure and high piezoelectricity of single crystal active materials, the actuators exhibit large linear displacement responses with negligible (<1%) hysteresis. Prototypes of square-pipe stake actuators were first fabricated and their phase transformation curves under different applied voltages, axial compressive loads and temperatures were established. Based on the information obtained, a range of Hi-Fi stake actuators with external square cross-sections of 5 × 5 mm2, 7.5 × 7.5 mm2 and 10 × 10 mm2, each of 4 different overall lengths of 15, 28, 41 and 54 mm, were further designed and fabricated using either PZN-PT or PIN-PMN-PT single crystals (both with TRO ≈ 110–125 °C) of 0.4 mm in crystal thickness. The stroke for the longest stake actuator fabricated (L = 54 mm) reaches −58 µm at 240 V. The working conditions, over which these Hi-Fi stake actuators remain linear with negligible hysteresis, were established for a total load of up to 10 kg and use temperature of up to 40 °C. Full article
(This article belongs to the Special Issue Piezoelectric Actuators 2018)
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Open AccessArticle Measurements versus Numerical Simulations for Slotted Synthetic Jet Actuator
Actuators 2018, 7(3), 59; https://doi.org/10.3390/act7030059
Received: 25 July 2018 / Revised: 7 September 2018 / Accepted: 10 September 2018 / Published: 11 September 2018
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Abstract
In many studies concerning synthetic jet flow fields the analysis is usually restricted to simple configurations, such as a single diaphragm oscillating in a cylindrical cavity, which is linked to the external environment with only one orifice/slot. Nonetheless, in many applications the requirement
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In many studies concerning synthetic jet flow fields the analysis is usually restricted to simple configurations, such as a single diaphragm oscillating in a cylindrical cavity, which is linked to the external environment with only one orifice/slot. Nonetheless, in many applications the requirement of small sizes and weights leads to many implementation issues, such as asymmetric actuator geometries, presence of several slots and diaphragms and irregular cavity shapes. Therefore, the design of a synthetic jet actuator for a specific flow control problem requires a dedicated study in order to characterize its behavior even in quiescent conditions. The aim of this work is to investigate the behavior of a novel synthetic jet actuator, composed of three independent diaphragms, acting on a single cavity, and linked to the external environment through four slots per diaphragm. The device has been studied in quiescent conditions, both numerically and experimentally. The experimental investigation has been carried out by means of hot-wire measurements. In particular, the distribution of the phase-averaged streamwise velocity along the slot spanwise direction has been detected near the slot exit plane. From the computational side, incompressible direct numerical simulations have been carried out using the open-source OpenFOAM code. The diaphragm motion is mimicked by a inhomogeneous inlet boundary condition, whose amplitude is chosen to match the experimental velocity at the exit plane. A fair agreement between the numerical and the experimental results is achieved for both the velocity field at the slot exit and the main non-dimensional parameters of the synthetic jet. After the validation, the numerical results are finally processed, to obtain information about the vortex motion in the external environment. Full article
(This article belongs to the Special Issue Synthetic Jet Actuators)
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Open AccessArticle Experimental Measurement Benchmark for Compressible Fluidic Unsteady Jet
Actuators 2018, 7(3), 58; https://doi.org/10.3390/act7030058
Received: 23 July 2018 / Revised: 20 August 2018 / Accepted: 6 September 2018 / Published: 10 September 2018
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Abstract
A benchmark of different measurement techniques is presented to characterize the dynamic response of a synthetic jet actuator working in compressible regime. The setup involves a piston-based synthetic jet, as well as the benchmarked measurements are hot-wire, cold-wire, Laser Doppler Anemometry, pressure transducer,
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A benchmark of different measurement techniques is presented to characterize the dynamic response of a synthetic jet actuator working in compressible regime. The setup involves a piston-based synthetic jet, as well as the benchmarked measurements are hot-wire, cold-wire, Laser Doppler Anemometry, pressure transducer, and Schlieren visualization. Measured flow temperatures range from 20 °C to 150 °C, pressure ranges from 0.5 atm to 4 atm, and velocity are up to 300 m/s. The extreme values of these ranges are reached in an oscillating fashion at a frequency ranging from 30 to 100 Hz. The measurements are pointing out the limitation of cold-wire measurements, due to its high thermic inertia. The results show consistency in the velocity measurements, within 10% in the worst case, between all measurement techniques and the errors are traced back to the calibration ranges, whose sensitivity is also studied. Full article
(This article belongs to the Special Issue Synthetic Jet Actuators)
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Open AccessArticle Scalloping and Stress Concentration in DRIE-Manufactured Comb-Drives
Actuators 2018, 7(3), 57; https://doi.org/10.3390/act7030057
Received: 23 July 2018 / Revised: 30 August 2018 / Accepted: 4 September 2018 / Published: 5 September 2018
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Abstract
In the last decades, microelectromechanical systems have been increasing their number of degrees of freedom and their structural complexity. Hence, most recently designed MEMSs have required higher mobility than in the past and higher structural strength and stability. In some applications, device thickness
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In the last decades, microelectromechanical systems have been increasing their number of degrees of freedom and their structural complexity. Hence, most recently designed MEMSs have required higher mobility than in the past and higher structural strength and stability. In some applications, device thickness increased up to the order of tens (or hundred) of microns, which nowadays can be easily obtained by means of DRIE Bosch process. Unfortunately, scalloping introduces stress concentration regions in some parts of the structure. Stress concentration is a dangerous source of strength loss for the whole structure and for comb-drives actuators which may suffer from side pull-in. This paper presents an analytical approach to characterize stress concentrations in DRIE micro-machined MEMS. The method is based on the linear elasticity equations, the de Saint-Venant Principle, and the boundary value problem for the case of a torsional state of the beam. The results obtained by means of this theoretical method are then compared with those obtained by using two other methods: one based on finite difference discretization of the equations, and one based on finite element analysis (FEA). Finally, the new theoretical approach yields results which are in accordance with the known value of the stress concentration factor for asymptotically null radius notches. Full article
(This article belongs to the Special Issue Micromanipulation)
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Open AccessArticle Learning Micromanipulation, Part 2: Term Projects in Practice
Actuators 2018, 7(3), 56; https://doi.org/10.3390/act7030056
Received: 3 August 2018 / Revised: 30 August 2018 / Accepted: 31 August 2018 / Published: 3 September 2018
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Abstract
This paper describes the activities that have been necessary to design, fabricate, control and test some low-cost test stands independently developed by the students enrolled in the course of Micro-Nano sensors and actuators for the postgraduate course in Industrial Nanotechnologies Engineering of the
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This paper describes the activities that have been necessary to design, fabricate, control and test some low-cost test stands independently developed by the students enrolled in the course of Micro-Nano sensors and actuators for the postgraduate course in Industrial Nanotechnologies Engineering of the University of Rome La Sapienza. The construction and use of these test stands are an essential part of teaching and learning methods whose theoretical bases have been presented in the companion paper (Part 1). Each test stand is composed of a compliant structure and a control system, which consists of a programmable control micro-card equipped with sensors and actuators. The compliant structure consists of a compliant mechanism whose geometry is achieved by scaling some previously developed silicon micromanipuators and microactuators up to the macroscale by a factor of 20. This macroscale model offered a kinesthetic tool to improve the understanding of the original microsystems and their working principles. The original silicon micromechanisms have been previously presented in the literature by the research group after design and deep reactive-ion etching (DRIE) microfabrication. Scaling from micro to macro size was quite easy because the original DRIE masks were bestowed to the students in the form of CAD files. The samples at the macroscale have been fabricated by means of recently available low-cost 3D printers after some necessary modifications of the mask geometry. The purpose of the whole work (Parts 1 and 2) was the improvement of the efficiency of an educational process in the field of microsystem science. By combining the two companion papers, concerning, respectively, the theoretical basis of the teaching methods and the students’ achievements, it is possible to conclude that, in a given class, there may be some preferred activities that are more efficient than others in terms of advancements and satisfaction. Full article
(This article belongs to the Special Issue Micromanipulation)
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Open AccessArticle Learning Micromanipulation, Part 1: An Approach Based on Multidimensional Ability Inventories and Text Mining
Actuators 2018, 7(3), 55; https://doi.org/10.3390/act7030055
Received: 3 August 2018 / Revised: 28 August 2018 / Accepted: 31 August 2018 / Published: 3 September 2018
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Abstract
In the last decades, an effort has been made to improve the efficiency of high-level and academic education players. Nowadays, students’ preferences and habits are continuously evolving and so the educational institutions deal with important challenges, such as not losing attractiveness or preventing
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In the last decades, an effort has been made to improve the efficiency of high-level and academic education players. Nowadays, students’ preferences and habits are continuously evolving and so the educational institutions deal with important challenges, such as not losing attractiveness or preventing early abandonment during the programs. In many countries, some important universities are public, and so they receive national grants that are based on a variety of factors, on which the teaching efficiency has a great impact. This contribution presents a method to improve students commitment during traditional lessons and laboratory tests. The idea consists in planning some activities according to the students’ learning preferences, which were studied by means of two different approaches. The first one was based on Gardner’s multiple intelligence inventory, which is useful to highlight some peculiar characteristics of the students on the specific educational field. In the second method, direct interviews, voice recognition, and text mining were used to extract some interesting characteristics of the group of students who participated in the projects. The methods were applied in May 2018 to the students attending the course of Micro-Nano Sensors and Actuators for the postgraduate academic program dedicated to Industrial Nanotechnologies Engineering of the University of Rome La Sapienza. The present paper represents the first part of the investigation and it is dedicated essentially to the adopted methods. The second part of the work is presented in the companion paper dedicated to the presentation of the practical project that the students completed before the exam. Full article
(This article belongs to the Special Issue Micromanipulation)
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Open AccessArticle Effect of Optimal Placement of Permanent Magnets on the Electromagnetic Force in the Horizontal Direction
Actuators 2018, 7(3), 54; https://doi.org/10.3390/act7030054
Received: 15 June 2018 / Revised: 3 August 2018 / Accepted: 24 August 2018 / Published: 29 August 2018
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Abstract
The surface quality of steel plates is deteriorated as they contact rollers while being conveyed during manufacturing processes. To solve this problem, we previously proposed a hybrid electromagnetic levitation system comprising electromagnets, permanent magnets, and a horizontal positioning control system for steel plates.
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The surface quality of steel plates is deteriorated as they contact rollers while being conveyed during manufacturing processes. To solve this problem, we previously proposed a hybrid electromagnetic levitation system comprising electromagnets, permanent magnets, and a horizontal positioning control system for steel plates. Moreover, to increase stability, we proposed integrating these levitation systems. In this study, we aim to determine the optimal placement of permanent magnets in the levitation system to suppress the deflection of a levitated steel plate for cases where the magnetic field in the horizontal direction changes. Using a genetic algorithm, the optimal gap, number, and placement of permanent magnets in the system are obtained. Full article
(This article belongs to the Special Issue Modeling Smart Actuators and Their Applications)
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Open AccessArticle Novel Nozzle Shapes for Synthetic Jet Actuators Intended to Enhance Jet Momentum Flux
Actuators 2018, 7(3), 53; https://doi.org/10.3390/act7030053
Received: 27 July 2018 / Revised: 14 August 2018 / Accepted: 25 August 2018 / Published: 28 August 2018
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Abstract
An axisymmetric synthetic jet actuator based on a loudspeaker and five types of flanged nozzles were experimentally tested and compared. The first (reference) type of nozzle was a common sharp-edged circular hole. The second type had a rounded lip on the inside. The
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An axisymmetric synthetic jet actuator based on a loudspeaker and five types of flanged nozzles were experimentally tested and compared. The first (reference) type of nozzle was a common sharp-edged circular hole. The second type had a rounded lip on the inside. The third nozzle type was assembled from these two types of nozzles—it had a rounded lip on the inside and straight section on the outside. The fourth nozzle was assembled using orifice plates such that the rounded lips were at both inner and outer nozzle ends. The last nozzle was equipped with an auxiliary nozzle plate placed at a small distance downstream of the main nozzle. The actuators with particular nozzles were tested by direct measurement of the synthetic jet (SJ) time-mean thrust using precision scales. Velocity profiles at the actuator nozzle exit were measured by a hot-wire anemometer. Experiments were performed at eight power levels and at the actuator resonance frequency. The highest momentum flux was achieved by the nozzle equipped with an auxiliary nozzle plate. Namely, an enhancement was approximately 31% in comparison with an effect of the reference nozzle at the same input power. Furthermore, based on the cavity pressure and the experimental velocity profiles, parameters for a lumped element model (mass of moving fluid and pressure loss coefficient) were evaluated. These values were studied as functions of the dimensionless stroke length. Full article
(This article belongs to the Special Issue Synthetic Jet Actuators)
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Open AccessArticle Development and Implementation of a Multi-Channel Active Control System for the Reduction of Road Induced Vehicle Interior Noise
Actuators 2018, 7(3), 52; https://doi.org/10.3390/act7030052
Received: 8 July 2018 / Revised: 17 August 2018 / Accepted: 21 August 2018 / Published: 27 August 2018
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Abstract
An optimized driving comfort with a low interior noise level is an important intention in the passenger car development process. The interior noise level caused by the dynamic interaction between the rolling tyre and the rough road surface and transmitted via the car-body
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An optimized driving comfort with a low interior noise level is an important intention in the passenger car development process. The interior noise level caused by the dynamic interaction between the rolling tyre and the rough road surface and transmitted via the car-body is a significant component of the entire noise level. To reduce the road induced interior noise, in general, the chassis system has to be optimized. Passive measures often induces a trade-off between vehicle dynamics and driving comfort. To overcome this disadvantage in this paper, the development and realization of an active measure is proposed. For the purpose of active mechanical decoupling, an active control system is developed, the feasibility of the integration is investigated and its noise reduction potential is identified by vehicle tests. In a first step, a classical multi-channel and experimental-based structure-borne transfer path analysis of the full vehicle is realized to determine the dominant transfer paths. The concept for the active mount system (active mounts, multi-channel control system, sensors) is developed and parametrized by system level simulation. Mechanical components and power electronics of the active system are designed, manufactured and tested in the laboratory. Subsequently, the entire active system is integrated into the vehicle. The broadband adaptive feedforward algorithm is extended by certain measures in order to improve robustness and performance. Full vehicle tests are used to quantify the required specifications and the achieved effectiveness of the active vibration control system. Full article
(This article belongs to the Special Issue Piezoelectric Actuators 2018)
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Open AccessArticle Dielectric Elastomer Actuators with Carbon Nanotube Electrodes Painted with a Soft Brush
Actuators 2018, 7(3), 51; https://doi.org/10.3390/act7030051
Received: 5 July 2018 / Revised: 19 August 2018 / Accepted: 21 August 2018 / Published: 22 August 2018
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Abstract
We propose a simple methodology to paint carbon nanotube (CNT) powder with a soft brush onto an elastomer. A large deformation of dielectric elastomer actuator (DEA) occurs according to the small constraint of the electrodes. Uniform painting with a soft brush leads to
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We propose a simple methodology to paint carbon nanotube (CNT) powder with a soft brush onto an elastomer. A large deformation of dielectric elastomer actuator (DEA) occurs according to the small constraint of the electrodes. Uniform painting with a soft brush leads to a stable deformation, as demonstrated by the results of multiple trials. Unexpectedly, painting with a soft brush results in aligned materials on the elastomer. The oriented materials demonstrate anisotropic mechanical and electronic properties. This simple methodology should help realize innovative DEA applications. Full article
(This article belongs to the Special Issue Electroactive Polymer Actuators for Soft Robotics)
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Open AccessFeature PaperArticle Dielectric Electroactive Polymers with Chemical Pre-Strain: An Experimentally Validated Model
Actuators 2018, 7(3), 50; https://doi.org/10.3390/act7030050
Received: 15 June 2018 / Revised: 28 July 2018 / Accepted: 15 August 2018 / Published: 22 August 2018
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Abstract
Dielectric electroactive polymer materials represent a distinct group of smart materials that are capable of converting between electrical and mechanical energy. This research focuses on the modeling and testing of an industrial grade fluoropolymer material for its feasibility as a dielectric elastomer electroactive
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Dielectric electroactive polymer materials represent a distinct group of smart materials that are capable of converting between electrical and mechanical energy. This research focuses on the modeling and testing of an industrial grade fluoropolymer material for its feasibility as a dielectric elastomer electroactive polymer. Through this process, a novel chemical pre-strain method was tested, along with a one-step process for application of pre-strain and addition of an elastomer conductive layer. Modeled and experimental actuators produced approximately 1 mm displacements with 0.625 W of electrical power. The displacement of the actuators was characterized, and the effects of multiple parameters were modeled and analyzed. Full article
(This article belongs to the Special Issue Modeling Smart Actuators and Their Applications)
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Open AccessArticle A Fundamental Consideration of Active Noise Control System by Small Actuator for Ultra-Compact EV
Actuators 2018, 7(3), 49; https://doi.org/10.3390/act7030049
Received: 15 June 2018 / Revised: 4 August 2018 / Accepted: 13 August 2018 / Published: 16 August 2018
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Abstract
The ultra-compact electric vehicle has recently experienced increasing popularity for short-distance travel. However, one of the issues with ultra-compact electric vehicles is that although the engine is silent, exterior road and wind noise have a significant impact on the occupant’s comfort in the
[...] Read more.
The ultra-compact electric vehicle has recently experienced increasing popularity for short-distance travel. However, one of the issues with ultra-compact electric vehicles is that although the engine is silent, exterior road and wind noise have a significant impact on the occupant’s comfort in the interior space. We propose an ANC system whereby a kind of small actuator is installed on the roof of an ultra-compact electric vehicle. In this paper, we consider the noise control effects of using a giant magnetostrictive actuator and conduct an experimental study on feed-forward and feedback control systems. Full article
(This article belongs to the Special Issue Modeling Smart Actuators and Their Applications)
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Open AccessFeature PaperReview An Overview of Novel Actuators for Soft Robotics
Actuators 2018, 7(3), 48; https://doi.org/10.3390/act7030048
Received: 10 June 2018 / Revised: 24 July 2018 / Accepted: 9 August 2018 / Published: 16 August 2018
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Abstract
In this systematic survey, an overview of non-conventional actuators particularly used in soft-robotics is presented. The review is performed by using well-defined performance criteria with a direction to identify the exemplary and potential applications. In addition to this, initial guidelines to compare the
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In this systematic survey, an overview of non-conventional actuators particularly used in soft-robotics is presented. The review is performed by using well-defined performance criteria with a direction to identify the exemplary and potential applications. In addition to this, initial guidelines to compare the performance and applicability of these novel actuators are provided. The meta-analysis is restricted to five main types of actuators: shape memory alloys (SMAs), fluidic elastomer actuators (FEAs), shape morphing polymers (SMPs), dielectric electro-activated polymers (DEAPs), and magnetic/electro-magnetic actuators (E/MAs). In exploring and comparing the capabilities of these actuators, the focus was on eight different aspects: compliance, topology-geometry, scalability-complexity, energy efficiency, operation range, modality, controllability, and technological readiness level (TRL). The overview presented here provides a state-of-the-art summary of the advancements and can help researchers to select the most convenient soft actuators using the comprehensive comparison of the suggested quantitative and qualitative criteria. Full article
(This article belongs to the Special Issue Robotic Actuators)
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Open AccessArticle Noncontact Guide System for Traveling Continuous Steel Plate Using Electromagnet and Supplement of Permanent Magnets for Suppressing Vibration
Actuators 2018, 7(3), 47; https://doi.org/10.3390/act7030047
Received: 15 June 2018 / Revised: 7 August 2018 / Accepted: 9 August 2018 / Published: 13 August 2018
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Abstract
In a plating process, the steel plate is conveyed 20–50 m in the vertical direction for drying, during which it is negligibly supported by rollers and other mechanisms. This produces plating without uniformity owing to the generation of vibration and other factors, which
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In a plating process, the steel plate is conveyed 20–50 m in the vertical direction for drying, during which it is negligibly supported by rollers and other mechanisms. This produces plating without uniformity owing to the generation of vibration and other factors, which prevent the increase in productivity. We have developed a noncontact guide system for a high-speed traveling elastic steel plate in which electromagnetic forces are applied by actuators at the edges of the plate to control the plate’s position. In this study, we investigated the vibration phenomenon when changing the steady current value of the electromagnet used for controlling the position. In addition, we conducted mode analysis of the steel plate to enable stable control even at low steady current values and verified whether stable guide can be provided by using it together with a permanent magnet. As a result, by arranging the permanent magnets, stable guidance was possible even at a low steady current value. In addition, it became clear that vibration damping performance is also improved. Full article
(This article belongs to the Special Issue Modeling Smart Actuators and Their Applications)
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Open AccessArticle Offset-Free Model Predictive Control for Active Magnetic Bearing Systems
Actuators 2018, 7(3), 46; https://doi.org/10.3390/act7030046
Received: 9 July 2018 / Revised: 1 August 2018 / Accepted: 6 August 2018 / Published: 7 August 2018
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Abstract
This paper presents the study of linear Offset-Free Model Predictive Control (OF-MPC) for an Active Magnetic Bearing (AMB) application. The method exploits the advantages of classical MPC in terms of stability and control performance and, at the same time, overcomes the effects of
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This paper presents the study of linear Offset-Free Model Predictive Control (OF-MPC) for an Active Magnetic Bearing (AMB) application. The method exploits the advantages of classical MPC in terms of stability and control performance and, at the same time, overcomes the effects of the plant-model mismatch on reference tracking. The proposed approach is based on a disturbance observer with an augmented plant model including an input disturbance estimation. Besides the abovementioned advantages, this architecture allows a real-time estimation of low-frequency disturbance, such as slow load variations. This property can be of great interest for a variety of AMB systems, particularly where the knowledge of the external load is important to regulate the behavior of the controlled plant. To this end, the paper describes the modeling and design of the OF-MPC architecture and its experimental validation for a one degree of freedom AMB system. The effectiveness of the method is demonstrated in terms of the reference tracking performance, cancellation of plant-model mismatch effects, and low-frequency disturbance estimation. Full article
(This article belongs to the Special Issue Magnetic Bearing Actuators)
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Open AccessArticle Modelling of a Partially Loaded Road Tanker during a Braking-in-a-Turn Maneuver
Actuators 2018, 7(3), 45; https://doi.org/10.3390/act7030045
Received: 27 June 2018 / Revised: 25 July 2018 / Accepted: 1 August 2018 / Published: 1 August 2018
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Abstract
Road safety depends on several factors associated with the vehicle, to the infrastructure, as well as to the environment and experience of vehicle drivers. Concerning the vehicle factors influencing the safety level of an infrastructure, it has been shown that the dynamic interaction
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Road safety depends on several factors associated with the vehicle, to the infrastructure, as well as to the environment and experience of vehicle drivers. Concerning the vehicle factors influencing the safety level of an infrastructure, it has been shown that the dynamic interaction between the carried liquid cargo and the vehicle influences the operational safety limits of the vehicle. A combination of vehicle and infrastructure factors converge when a vehicle carrying liquid cargo at a partial fill level performs a braking maneuver along a curved road segment. Such a maneuver involves both longitudinal and lateral load transfers that potentially affect both the braking efficiency and the lateral stability of the vehicle. In this paper, a series of models are set together to simulate the effects of a sloshing cargo on the braking efficiency and load transfer rate of a partially filled road tanker. The model assumes the superposition of the roll and pitch independent responses, while the vehicle is equipped with Anti-lock braking System brakes (ABS) in the four wheels. Results suggest that cargo sloshing can affect the performance of the vehicle on the order of 2% to 9%, as a function of the performance measure considered. A dedicated ABS system could be considered to cope with such diminished performance. Full article
(This article belongs to the Special Issue Novel Braking Control Systems)
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Open AccessArticle Driving Assist System for Ultra-Compact EVs―Fundamental Consideration of Muscle Burden Owing to Differences in the Drivers’ Physiques
Actuators 2018, 7(3), 44; https://doi.org/10.3390/act7030044
Received: 15 June 2018 / Revised: 20 July 2018 / Accepted: 24 July 2018 / Published: 27 July 2018
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Abstract
With recent advances in technologies such as those of semiconductors and actuators, easy-to-control compact actuators have been actively applied in various fields such as factory automation and precision machining. In the automobile industry, major manufacturers and venture companies are also concentrating on electric
[...] Read more.
With recent advances in technologies such as those of semiconductors and actuators, easy-to-control compact actuators have been actively applied in various fields such as factory automation and precision machining. In the automobile industry, major manufacturers and venture companies are also concentrating on electric vehicle development. Ultra-compact mobility vehicles, which exhibit an excellent environmental performance and are highly convenient for short-distance movement, are becoming popular. However, owing to cabin space limitations, it is difficult to mount systems such as power steering for assisting steering operations, and such systems are currently not installed in most ultra-compact mobility vehicles. Our research group focused on a steer-by-wire system that does not require a physical connection between the steering wheel and the wheels. Using this system, the steering wheel can be installed without any constraints, and the cabin layout can be easily changed. The reaction torque applied to the steering wheel can be expected to provide an optimum steering feel to each driver by controlling the reaction-force-generating actuator output. Drivers with different heights and arm lengths were then grouped, and arm model calculation and electromyogram measurements obtained during steering operations were used to examine the muscle burden experienced during driving owing to differences in the drivers’ physiques. Full article
(This article belongs to the Special Issue Modeling Smart Actuators and Their Applications)
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Open AccessArticle Electromagnetic Levitation Control for Bending Flexible Steel Plate: Experimental Consideration on Disturbance Cancellation Control
Actuators 2018, 7(3), 43; https://doi.org/10.3390/act7030043
Received: 15 June 2018 / Revised: 20 July 2018 / Accepted: 24 July 2018 / Published: 27 July 2018
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Abstract
When an ultrathin and flexible steel plate is to be levitated, levitation control becomes difficult because the ultrathin steel plate undergoes increased flexure. We herein propose a levitation method for an ultrathin steel plate that is bent to an extent that does not
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When an ultrathin and flexible steel plate is to be levitated, levitation control becomes difficult because the ultrathin steel plate undergoes increased flexure. We herein propose a levitation method for an ultrathin steel plate that is bent to an extent that does not induce plastic deformation. In this study, to investigate the levitation stability of an ultrathin steel plate, we applied disturbance cancellation control in the bending levitation system. The object of electromagnetic levitation was a rectangular zinc-coated ultrathin steel plate (SS400) of length 800 mm, 600 mm, and thickness 0.19 mm. The vibrator was attached below the three frames, in which the electromagnet unit was installed so that the frames could be vibrated up and down. We conducted experiments on the levitation performance when the electromagnet was displaced by the frame vibration in the bending levitation system. The results showed that a stable levitation can be achieved even with an input of external disturbance when levitating at the optimum bending angle. Full article
(This article belongs to the Special Issue Modeling Smart Actuators and Their Applications)
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Open AccessArticle Ride Comfort Control System Considering Physiological and Psychological Characteristics: Effect of Masking on Vertical Vibration on Passengers
Actuators 2018, 7(3), 42; https://doi.org/10.3390/act7030042
Received: 15 June 2018 / Revised: 16 July 2018 / Accepted: 20 July 2018 / Published: 23 July 2018
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Abstract
Active seat suspension has been proposed to improve ride comfort for ultra-compact mobility. Regarding the ride comfort of passengers due to vertical vibration, the authors have confirmed from biometry measurements that reduction of the vibration acceleration does not always produce the best ride
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Active seat suspension has been proposed to improve ride comfort for ultra-compact mobility. Regarding the ride comfort of passengers due to vertical vibration, the authors have confirmed from biometry measurements that reduction of the vibration acceleration does not always produce the best ride comfort for passengers. Therefore, heart rate variability that can quantitatively reflect stress is measured in real time, and a control method was proposed that feeds back to active suspension and confirms its effectiveness by fundamental verification. In this paper, we will confirm the influence of the vibration stress on the psychological state of the occupant by the masking method. Full article
(This article belongs to the Special Issue Modeling Smart Actuators and Their Applications)
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Open AccessFeature PaperArticle Passive Damping of Rotationally Periodic Structures with Tuned Piezoelectric Inductive Shunt
Actuators 2018, 7(3), 41; https://doi.org/10.3390/act7030041
Received: 28 May 2018 / Revised: 20 June 2018 / Accepted: 18 July 2018 / Published: 19 July 2018
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Abstract
This paper considers the piezoelectric resistive and inductive RL shunt damping applied to rotationally periodic structures equipped with an array of regularly spaced piezoelectric patches. A method for simplifying the hardware, by reducing the size of the inductors and eliminating the use of
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This paper considers the piezoelectric resistive and inductive RL shunt damping applied to rotationally periodic structures equipped with an array of regularly spaced piezoelectric patches. A method for simplifying the hardware, by reducing the size of the inductors and eliminating the use of synthetic inductors, is described. The paper compares two different ways of using the piezoelectric array: independent loops and parallel loops. It shows that, if a specific mode with n nodal diameters is targeted, mounting 4n piezoelectric patches in two parallel loops is as efficient as mounting them in 4n independent loops, while considerably reducing the demand on the inductors, L, (by 4n2). The method takes advantage of the mode shapes of rotationally periodic structures. The proposed method is validated numerically and experimentally on a rotationally periodic circular plate (nearly axisymmetric). The proposed technique is aimed at turbomachinery applications. Full article
(This article belongs to the Special Issue Piezoelectric Actuators 2018)
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Open AccessFeature PaperArticle Sleeved Bending Actuators for Soft Grippers: A Durable Solution for High Force-to-Weight Applications
Actuators 2018, 7(3), 40; https://doi.org/10.3390/act7030040
Received: 6 June 2018 / Revised: 12 July 2018 / Accepted: 13 July 2018 / Published: 17 July 2018
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Abstract
Soft grippers are known for their ability to interact with objects that are fragile, soft or of an unknown shape, as well as humans in collaborative robotics applications. However, state-of-the-art soft grippers lack either payload capacity or durability, which limits their use in
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Soft grippers are known for their ability to interact with objects that are fragile, soft or of an unknown shape, as well as humans in collaborative robotics applications. However, state-of-the-art soft grippers lack either payload capacity or durability, which limits their use in industrial applications. In fact, high force density pneumatic soft grippers require high strain and operating pressure, both of which impair their durability. This work presents a new sleeved bending actuator for soft grippers that is capable of high force density and durability. The proposed actuator is based on design principles previously proven to improve the life of pneumatic artificial muscles, where a sleeve provides a uniform reinforcement that reduces local stresses and strains in the inflated membrane. The sleeved bending actuator features a silicone membrane and an external two-material sleeve that can support high pressures while providing a flexible grip. The proposed sleeved bending actuators are validated through two grippers, sized according to foreseen soft gripper applications: A small gripper for drone perching and lightweight food manipulation, and a larger one for the manipulation of heavy material (>5 kg) of various weights and sizes. Performance assessment shows that these grippers have payloads up to 5.2 kg and 20 kg, respectively. Durability testing of the grippers demonstrates that the grippers have an expected lifetime ranging from 263,000 cycles to more than 700,000 cycles. The grippers are tested in various settings, including the integration of a gripper into a Phantom 2 quadcopter, a perching demonstration, as well as the gripping of light and heavy food items. Experiments show that sleeved bending actuators constitute a promising avenue for durable and strong soft grippers. Full article
(This article belongs to the Special Issue Pneumatic Actuators)
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Open AccessArticle Coevolution of the Features of the Dynamics of the Accelerator Pedal and Hyperparameters of the Classifier for Emergency Braking Detection
Actuators 2018, 7(3), 39; https://doi.org/10.3390/act7030039
Received: 26 June 2018 / Revised: 12 July 2018 / Accepted: 13 July 2018 / Published: 16 July 2018
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Abstract
We investigate the feasibility of inferring the intention of the human driver of road motor vehicles to apply emergency braking solely by analyzing the dynamics of lifting the accelerator pedal. Focusing on building the system that reliably classifies the emergency braking situations, we
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We investigate the feasibility of inferring the intention of the human driver of road motor vehicles to apply emergency braking solely by analyzing the dynamics of lifting the accelerator pedal. Focusing on building the system that reliably classifies the emergency braking situations, we employed evolutionary algorithms (EA) to coevolve both (i) the set of features that optimally characterize the movement of accelerator pedal and (ii) the values of the hyperparameters of the classifier. The experimental results demonstrate the superiority of the coevolutionary approach over the analogical approaches that rely on an a priori defined set of features and values of hyperparameters. By using simultaneous evolution of both features and hyperparameters, the learned classifier inferred the emergency braking situations in previously unforeseen dynamics of the accelerator pedal with an accuracy of about 95%. We consider the obtained results as a step towards the development of a brake-assisting system, which would perceive the dynamics of the accelerator pedal in a real-time and in case of a foreseen emergency braking situation, would apply the brakes automatically well before the human driver would have been able to apply them. Full article
(This article belongs to the Special Issue Novel Braking Control Systems)
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Open AccessArticle The Effects of Structure Thickness, Air Gap Thickness and Silicon Type on the Performance of a Horizontal Electrothermal MEMS Microgripper
Actuators 2018, 7(3), 38; https://doi.org/10.3390/act7030038
Received: 20 June 2018 / Revised: 9 July 2018 / Accepted: 11 July 2018 / Published: 15 July 2018
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Abstract
The ongoing development of microelectromechanical systems (MEMS) over the past decades has made possible the achievement of high-precision micromanipulation within the micromanufacturing, microassembly and biomedical fields. This paper presents different design variants of a horizontal electrothermally actuated MEMS microgripper that are developed as
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The ongoing development of microelectromechanical systems (MEMS) over the past decades has made possible the achievement of high-precision micromanipulation within the micromanufacturing, microassembly and biomedical fields. This paper presents different design variants of a horizontal electrothermally actuated MEMS microgripper that are developed as microsystems to micromanipulate and study the deformability properties of human red blood cells (RBCs). The presented microgripper design variants are all based on the U-shape ‘hot and cold arm’ actuator configuration, and are fabricated using the commercially available Multi-User MEMS Processes (MUMPs®) that are produced by MEMSCAP, Inc. (Durham, NC, USA) and that include both surface micromachined (PolyMUMPs™) and silicon-on-insulator (SOIMUMPs™) MEMS fabrication technologies. The studied microgripper design variants have the same in-plane geometry, with their main differences arising from the thickness of the fabricated structures, the consequent air gap separation between the structure and the substrate surface, as well as the intrinsic nature of the silicon material used. These factors are all inherent characteristics of the specific fabrication technologies used. PolyMUMPs™ utilises polycrystalline silicon structures that are composed of two free-standing, independently stackable structural layers, enabling the user to achieve structure thicknesses of 1.5 μm, 2 μm and 3.5 μm, respectively, whereas SOIMUMPs™ utilises a 25 μm thick single crystal silicon structure having only one free-standing structural layer. The microgripper design variants are presented and compared in this work to investigate the effect of their differences on the temperature distribution and the achieved end-effector displacement. These design variants were analytically studied, as well as numerically modelled using finite element analysis where coupled electrothermomechanical simulations were carried out in CoventorWare® (Version 10, Coventor, Inc., Cary, NC, USA). Experimental results for the microgrippers’ actuation under atmospheric pressure were obtained via optical microscopy studies for the PolyMUMPs™ structures, and they were found to be conforming with the predictions of the analytical and numerical models. The focus of this work is to identify which one of the studied design variants best optimises the microgripper’s electrothermomechanical performance in terms of a sufficient lateral tip displacement, minimum out-of-plane displacement at the arm tips and good heat transfer to limit the temperature at the cell gripping zone, as required for the deformability study of RBCs. Full article
(This article belongs to the Special Issue Micromanipulation)
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Open AccessArticle A Bouc–Wen Model-Based Compensation of the Frequency-Dependent Hysteresis of a Piezoelectric Actuator Exhibiting Odd Harmonic Oscillation
Actuators 2018, 7(3), 37; https://doi.org/10.3390/act7030037
Received: 30 April 2018 / Revised: 4 July 2018 / Accepted: 4 July 2018 / Published: 6 July 2018
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Abstract
This paper proposes an enhancement of the Bouc–Wen hysteresis model to capture the frequency-dependent hysteretic behavior of a thin bimorph-type piezoelectric actuator which also exhibits odd harmonic oscillation (OHO) at specific input frequencies. The odd harmonic repetitive controller has recently been proposed to
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This paper proposes an enhancement of the Bouc–Wen hysteresis model to capture the frequency-dependent hysteretic behavior of a thin bimorph-type piezoelectric actuator which also exhibits odd harmonic oscillation (OHO) at specific input frequencies. The odd harmonic repetitive controller has recently been proposed to compensate for the hysteresis, and attenuates the OHO of the piezoelectric actuator for which the hysteresis nonlinearity is regarded as a disturbance. This paper proposes an alternate treatment of the hysteresis compensation with the attenuation of the OHO observed at some input frequencies. It will be shown that the proposed compensator fully utilizes the mathematical structure of the enhanced Bouc–Wen model proposed in this paper to compensate the hysteresis and to attenuate the OHO. The results of the hysteresis compensation experiment illustrate the excellent performance of the proposed control system, especially at the frequencies where OHO is conspicuous. Full article
(This article belongs to the Special Issue Piezoelectric Actuators 2018)
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Open AccessArticle Control of Pneumatic Artificial Muscles Using Local Cyclic Inputs and Genetic Algorithm
Actuators 2018, 7(3), 36; https://doi.org/10.3390/act7030036
Received: 26 April 2018 / Revised: 29 June 2018 / Accepted: 29 June 2018 / Published: 3 July 2018
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Abstract
Recently, lightweight and flexible soft actuators have attracted interest from robotics researchers. We focused on pneumatic rubber artificial muscle (PAM) as a high-output soft actuator. The high compliance of PAM allows a robot to adapt flexibly to the environment without many external sensors.
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Recently, lightweight and flexible soft actuators have attracted interest from robotics researchers. We focused on pneumatic rubber artificial muscle (PAM) as a high-output soft actuator. The high compliance of PAM allows a robot to adapt flexibly to the environment without many external sensors. Although PAM has these characteristics, it is difficult to control because of the nonlinearity between the input and output and the delay of air response. This limits the accuracy of artificial muscles and complicates motion planning. Therefore, we considered that PAM can be driven by simplified control laws, so that the entire system shows emergent motion guided by metaheuristics. We developed a legged robot with two joints driven by PAMs. Each PAM was controlled with a cyclic signal, and the genetic algorithm was applied to optimize these signals. We tested to check whether the behavior of the PAMs is changed by the genetic algorithm using three simple performance indexes. We found out that although the genetic algorithm adjusted the local cyclic inputs appropriately according to each performance index, the time-varying characteristic of PAMs disturbed the monotonic increment of the evaluation values. We also discovered that by only adjusting the input timing, the leg develops a limitation in robustness. Full article
(This article belongs to the Special Issue Pneumatic Actuators)
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Open AccessArticle The Flux-Based Sensorless Field-Oriented Control of Permanent Magnet Synchronous Motors without Integrational Drift
Actuators 2018, 7(3), 35; https://doi.org/10.3390/act7030035
Received: 16 May 2018 / Revised: 26 June 2018 / Accepted: 29 June 2018 / Published: 3 July 2018
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Abstract
The magnitude of the rotor magnetic flux linkage and its spatial orientation within a permanent magnet synchronous motor directly define the angular position of the rotor and are thus used in many sensorless applications as the governing variables. The rotor magnetic flux linkage
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The magnitude of the rotor magnetic flux linkage and its spatial orientation within a permanent magnet synchronous motor directly define the angular position of the rotor and are thus used in many sensorless applications as the governing variables. The rotor magnetic flux linkage in the stator reference frame is represented by two orthogonal sinusoids whose amplitudes and phases are determined by the integration of the orthogonal components of the corresponding voltage, which, due to DC offsets and initial conditions at transient states, result in an integrational drift. This paper proposes a solution to the problem of such integrational drift in the form of a compensation based only on orthogonal properties of waveforms in the stator reference frame. That makes it completely independent of electrical parameters of the motor. As a result, the proposed compensation of the integrational drift does not require any optimization by the user and it is functional from a standstill. The effectiveness of the proposed compensation is demonstrated analytically, by a simulation, and an experiment on a real motor by a simple observer for the sensorless field-oriented control based on the voltage model in the stator reference frame. Full article
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Open AccessArticle Mathematical Simulations and Analyses of Proportional Electro-Hydraulic Brakes and Anti-Lock Braking Systems in Motorcycles
Actuators 2018, 7(3), 34; https://doi.org/10.3390/act7030034
Received: 21 May 2018 / Revised: 16 June 2018 / Accepted: 28 June 2018 / Published: 30 June 2018
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Abstract
In the motorcycle industry, the safety of motorcycles operating at high speeds has received increasing attention. If a motorcycle is equipped with an anti-lock braking system (ABS), it can automatically adjust the size of the brake force to prevent the wheels from locking
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In the motorcycle industry, the safety of motorcycles operating at high speeds has received increasing attention. If a motorcycle is equipped with an anti-lock braking system (ABS), it can automatically adjust the size of the brake force to prevent the wheels from locking and achieve an optimal braking effect, ensuring operation stability. In an ABS, the brake force is controlled by an electro-hydraulic brake (EHB). The control valve inside the EHB was replaced with a proportional valve in this study, which differed from the general use of a solenoid valve. The purpose for this change was to precisely control the brake force and prevent hydraulic pressure oscillating in the piping. This study employed MATLAB/Simulink and block diagrams to establish a complete motorcycle ABS simulation model, including a proportional electro-hydraulic brake (PEHB), motorcycle motion, tire, and controller models. In an analysis of ABS simulation results, when traveling on different road surfaces, the PEHB could effectively reduce braking distance and solve the problem of hydraulic pressure oscillation during braking. The research demonstrated that this proportional pressure control valve can substitute the general solenoid valve in commercial braking systems. This can assist the ABS in achieving more precise slip control and improved motorcycle safety. Full article
(This article belongs to the Special Issue Novel Braking Control Systems)
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Open AccessFeature PaperArticle Simple Controller Design Based on Internal Model Control for Twisted and Coiled Polymer Actuator
Actuators 2018, 7(3), 33; https://doi.org/10.3390/act7030033
Received: 25 May 2018 / Revised: 19 June 2018 / Accepted: 21 June 2018 / Published: 25 June 2018
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Abstract
A twisted and coiled polymer actuator (TCPA) is a novel soft actuator. TCPA is fabricated by twisting nylon fibers. The TCPA extends and contracts by heating and cooling. By applying conductive nylon fibers to the actuator, the electroactive TCPA can be driven by
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A twisted and coiled polymer actuator (TCPA) is a novel soft actuator. TCPA is fabricated by twisting nylon fibers. The TCPA extends and contracts by heating and cooling. By applying conductive nylon fibers to the actuator, the electroactive TCPA can be driven by the Joule heating of the applied voltage. It has noteworthy properties such as a high power/mass ratio, large deformation, and low hysteresis. By applying conductive nylon fibers to the actuator, it can be driven by the electrical input. From these properties, many soft robots using the electroactive TCPA have been demonstrated, such as robotic hands, locomotion robots, robot skins, biomimetic robots, and so on. In this paper, to realize a simple controller design, an internal model control based on the identified model is applied. The applied controller can be designed easily without experience in parameter-tuning based on controls theory. The validity of the applied method is investigated through experiments. Full article
(This article belongs to the Special Issue Electroactive Polymer Actuators for Soft Robotics)
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