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Actuators, Volume 6, Issue 2 (June 2017)

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Research

Open AccessArticle Measuring the Temperature Increase of an Ultrasonic Motor in a 3-Tesla Magnetic Resonance Imaging System
Actuators 2017, 6(2), 20; doi:10.3390/act6020020
Received: 18 January 2017 / Revised: 29 May 2017 / Accepted: 29 May 2017 / Published: 6 June 2017
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Abstract
This paper aims to evaluate the temperature increase caused by a 3.0-T magnetic resonance imaging (MRI) system on an ultrasonic motor (USM) used to actuate surgical robots in the MRI environment. Four fiber-optic temperature sensors were attached to the USM. Temperature was monitored
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This paper aims to evaluate the temperature increase caused by a 3.0-T magnetic resonance imaging (MRI) system on an ultrasonic motor (USM) used to actuate surgical robots in the MRI environment. Four fiber-optic temperature sensors were attached to the USM. Temperature was monitored outside the five-Gauss boundary and then inside the bore for 20 min while the USM was powered on. The USM temperature was tested for two states of the scanner, “off” and “on”, by employing common clinical imaging sequences and echo planar imaging sequences. The USM showed a slight temperature increase while operating in the static field of the MRI. A considerable temperature increase (~10 °C) was observed when the scanner was on. The temperature increased to 60 °C, which is beyond the acceptable safe temperature and can result in thermal burns. Most of the temperature increase (80%) was due to effects of the static field on the motion of the rotating parts of the motor, while the remainder (20%) derived from heat deposited in the conductive components of the USM due to radiofrequency pulses and gradient field changes. To solve the temperature increase, the metal components of the USM’s case can be replaced by silicon carbide. Full article
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Open AccessFeature PaperArticle Modeling and Realization of a Bearingless Flux-Switching Slice Motor
Actuators 2017, 6(2), 12; doi:10.3390/act6020012
Received: 20 December 2016 / Revised: 10 March 2017 / Accepted: 22 March 2017 / Published: 27 March 2017
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Abstract
This work introduces a novel bearingless slice motor design: the bearingless flux-switching slice motor. In contrast to state-of-the-art bearingless slice motors, the rotor in this new design does not include any permanent rotor magnets. This offers advantages for disposable devices, such as those
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This work introduces a novel bearingless slice motor design: the bearingless flux-switching slice motor. In contrast to state-of-the-art bearingless slice motors, the rotor in this new design does not include any permanent rotor magnets. This offers advantages for disposable devices, such as those used in the medical industry, and extends the range of bearingless slice motors toward high-temperature applications. In this study, our focus is on the analytical modeling of the suspension force torque generation of a single coil and the bearingless motor. We assessed motor performance in relation to motor topology by applying performance factors. A prototype motor was optimized, designed, and manufactured. We also presented the state-of-the-art nonlinear feedback control scheme used. The motor was operated, and both static and dynamic measurements were taken on a test bench, thus successfully demonstrating the functionality and applicability of the novel bearingless slice motor concept. Full article
(This article belongs to the Special Issue Active Magnetic Bearing Actuators)
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Open AccessArticle A System Identification Technique Using Bias Current Perturbation for the Determination of the Magnetic Axes of an Active Magnetic Bearing
Actuators 2017, 6(2), 13; doi:10.3390/act6020013
Received: 14 December 2016 / Revised: 8 February 2017 / Accepted: 2 March 2017 / Published: 28 March 2017
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Abstract
Inherent in every Active Magnetic Bearing (AMB) are differences between the expected geometric axes and the actual magnetic axes due to a combination of discrepancies, including physical variation from manufacturing tolerances and misalignment from mechanical assembly, fringing and leakage effects, as well as
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Inherent in every Active Magnetic Bearing (AMB) are differences between the expected geometric axes and the actual magnetic axes due to a combination of discrepancies, including physical variation from manufacturing tolerances and misalignment from mechanical assembly, fringing and leakage effects, as well as variations in magnetic material properties within a single AMB. A method is presented here for locating the magnetic axes of an AMB that will facilitate the accurate characterization of the bearing air gaps for potential improvement in field tuning, performance analyses and certain shaft force measurement techniques. This paper presents an extension of the application of the bias current perturbation method for the determination of the magnetic center to the determination of magnetic axes for the further development of accurate current-based force measurement techniques. Full article
(This article belongs to the Special Issue Active Magnetic Bearing Actuators)
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Open AccessFeature PaperArticle Development of a Compact Axial Active Magnetic Bearing with a Function of Two-Tilt-Motion Control
Actuators 2017, 6(2), 14; doi:10.3390/act6020014
Received: 15 December 2016 / Revised: 9 March 2017 / Accepted: 28 March 2017 / Published: 30 March 2017
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Abstract
A compact axial active magnetic bearing with a function of two-tilt-motion control is fabricated which has a new configuration of magnetic poles. They consist of four cylindrical poles with coils and a single common pole whose opposite plane of the rotor has a
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A compact axial active magnetic bearing with a function of two-tilt-motion control is fabricated which has a new configuration of magnetic poles. They consist of four cylindrical poles with coils and a single common pole whose opposite plane of the rotor has a permanent magnet to achieve multi-degree-of-freedom zero power control. Modal control is applied because local zero power control may make the whole system unstable when the number of control channels is larger than the number of freedoms of motion to be controlled. In the developed system, a disk-shape rotor is sandwiched between two axial magnetic bearing stators that are operated differentially. Such a configuration makes it possible to rotate the rotor without disturbing the axial motion. The characteristics of the fabricated magnetic bearing system including rotation are studied experimentally. Full article
(This article belongs to the Special Issue Active Magnetic Bearing Actuators)
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Open AccessArticle Power Split Based Dual Hemispherical Continuously Variable Transmission
Actuators 2017, 6(2), 15; doi:10.3390/act6020015
Received: 26 February 2017 / Revised: 17 March 2017 / Accepted: 29 March 2017 / Published: 10 April 2017
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Abstract
In this work, we present a new continuously variable transmission concept: the Dual-Hemi Continuously Variable Transmission (CVT). It is designed to have properties we believe are required to apply continuously variable transmissions in robotics to their full potential. These properties are a transformation
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In this work, we present a new continuously variable transmission concept: the Dual-Hemi Continuously Variable Transmission (CVT). It is designed to have properties we believe are required to apply continuously variable transmissions in robotics to their full potential. These properties are a transformation range that includes both positive and negative ratios, back-drivability under all conditions, kinematically decoupled reconfiguration, high efficiency of the transmission, and a reconfiguration mechanism requiring little work for changing the transmission ratio. The design of the Dual-Hemi CVT and a prototype realisation are discussed in detail. We show that the Dual-Hemi CVT has the aforementioned desired properties. Experiments show that the efficiency of the CVT is above 90% for a large part of the range of operation of the CVT. Significant stiction in the transmission, combined with a relatively low bandwidth for changing the transmission ratio, may cause problems when applying the DH-CVT as part of an actuator in a control loop. Full article
(This article belongs to the Special Issue Variable Stiffness and Variable Impedance Actuators)
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Open AccessArticle Design and Evaluation of a Semi-Active Magneto-rheological Mount for a Wheel Loader Cabin
Actuators 2017, 6(2), 16; doi:10.3390/act6020016
Received: 2 January 2017 / Revised: 3 April 2017 / Accepted: 18 April 2017 / Published: 20 April 2017
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Abstract
In this study, a semi-active magneto-rheological (MR) mount is designed and manufactured to minimize unwanted vibrations for the cabin of heavy vehicles. Normally, working conditions in heavy vehicles are extremely rugged. Usually, the heavy vehicles use passive rubber mounts for the reduction of
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In this study, a semi-active magneto-rheological (MR) mount is designed and manufactured to minimize unwanted vibrations for the cabin of heavy vehicles. Normally, working conditions in heavy vehicles are extremely rugged. Usually, the heavy vehicles use passive rubber mounts for the reduction of vibrations from road. However, the passive mount has definite performance limitations because the passive mount has a fixed resonance frequency when the design is finished. An MR application is one of the solutions because the viscosity of MR fluid can be controlled. As a first step, an experimental apparatus was established for performance evaluation of the mounts. The apparatus has hydraulic excitatory, force, and displacement sensors. Performance of two different passive mounts used in industrial fields were evaluated. The passive mount data of force-displacement, force-velocity, and displacement transmissibility were collected and tested. After that, an MR mount was designed and manufactured that provides better performance using the passive mount data. The MR mount uses two different flow paths, annular duct and radial channels, for generating the required damping force. The field-dependent damping forces were then evaluated with respect to the moving stroke and input current. In this work, in order to control the damping force, an on-off controller associated with the fast Fourier transform (FFT) was used. The control results of the MR mount were compared with the results of passive rubber mounts. It was shown that the semi-active MR mount can attenuate vibrations more effectively at all frequency ranges compared with the passive rubber mount. Full article
(This article belongs to the Special Issue Magnetorheological Fluids, Devices, and Integrated Adaptive Systems)
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Open AccessArticle Environmental Effects on the Polypyrrole Tri-layer Actuator
Actuators 2017, 6(2), 17; doi:10.3390/act6020017
Received: 16 February 2017 / Revised: 10 April 2017 / Accepted: 23 April 2017 / Published: 26 April 2017
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Abstract
Electroactive polymer actuators such as polypyrrole (PPy) are exciting candidates to drive autonomous devices that require low weight and low power. A simple PPy tri-layer bending type cantilever which operates in the air has been demonstrated previously, but the environmental effect on this
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Electroactive polymer actuators such as polypyrrole (PPy) are exciting candidates to drive autonomous devices that require low weight and low power. A simple PPy tri-layer bending type cantilever which operates in the air has been demonstrated previously, but the environmental effect on this actuator is still unknown. The major obstacle in the development of the PPy tri-layer actuator is to create proper packaging that reduces oxidation of the electrolyte and maintains constant displacement. Here, we report the variation in the displacement as well as the charge transfer at the different environmental condition. PPy trilayer actuators were fabricated by depositing polypyrrole on gold-coated porous poly(vinylidene fluoride) (PVDF) using the electro-synthesis method. It has been demonstrated that the charge transfer of tri-layer actuators is more in an inert environment than in open air. In addition, tri-layer actuators show constant deflection and enhancement of life due to the negligible oxidation rate of the electrolyte in an inert environment. Full article
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Open AccessFeature PaperArticle Static and Dynamic Studies of Electro-Active Polymer Actuators and Integration in a Demonstrator
Actuators 2017, 6(2), 18; doi:10.3390/act6020018
Received: 30 January 2017 / Revised: 9 April 2017 / Accepted: 27 April 2017 / Published: 4 May 2017
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Abstract
Nowadays, the haptic effect is used and developed for many applications—particularly in the automotive industry, where the mechanical feedback induced by a haptic system enables the user to receive information while their attention is kept on the road and on driving. This article
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Nowadays, the haptic effect is used and developed for many applications—particularly in the automotive industry, where the mechanical feedback induced by a haptic system enables the user to receive information while their attention is kept on the road and on driving. This article presents the development of a vibrotactile button based on printed piezoelectric polymer actuation. Firstly, the characterization of the electro-active polymer used as the actuator and the development of a model able to predict the electromechanical behavior of this device are summarized. Then, the design of circular membranes and their dynamic characterization are presented. Finally, this work is concluded with the construction of a fully functional demonstrator, integrating haptic buttons leading to a clear haptic sensation for the user. Full article
(This article belongs to the Special Issue MEMS-based Actuators)
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Open AccessArticle Design and Characterization of In-Plane Piezoelectric Microactuators
Actuators 2017, 6(2), 19; doi:10.3390/act6020019
Received: 28 February 2017 / Revised: 30 May 2017 / Accepted: 1 June 2017 / Published: 3 June 2017
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Abstract
In this paper, two different piezoelectric microactuator designs are studied. The corresponding devices were designed for optimal in-plane displacements and different high flexibilities, proven by electrical and optical characterization. Both actuators presented two dominant vibrational modes in the frequency range below 1 MHz:
[...] Read more.
In this paper, two different piezoelectric microactuator designs are studied. The corresponding devices were designed for optimal in-plane displacements and different high flexibilities, proven by electrical and optical characterization. Both actuators presented two dominant vibrational modes in the frequency range below 1 MHz: an out-of-plane bending and an in-plane extensional mode. Nevertheless, the latter mode is the only one that allows the use of the device as a modal in-plane actuator. Finite Element Method (FEM) simulations confirmed that the displacement per applied voltage was superior for the low-stiffness actuator, which was also verified through optical measurements in a quasi-static analysis, obtaining a displacement per volt of 0.22 and 0.13 nm/V for the low-stiffness and high-stiffness actuator, respectively. In addition, electrical measurements were performed using an impedance analyzer which, in combination with the optical characterization in resonance, allowed the determination of the electromechanical and stiffness coefficients. The low-stiffness actuator exhibited a stiffness coefficient of 5 × 104 N/m, thus being more suitable as a modal actuator than the high-stiffness actuator with a stiffness of 2.5 × 105 N/m. Full article
(This article belongs to the Special Issue MEMS-based Actuators)
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