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Actuators, Volume 6, Issue 1 (March 2017) – 11 articles

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6902 KiB  
Article
The Proposal of Magnetic Suspension using Laterally Control Flux-Path Mechanism
by Naoki Ishibashi, Takeshi Mizuno, Yuji Ishino, Daisuke Yamaguchi, Masayuki Hara, Masaya Takasaki and Kazuki Yamada
Actuators 2017, 6(1), 11; https://doi.org/10.3390/act6010011 - 21 Mar 2017
Cited by 6 | Viewed by 6933
Abstract
A novel flux control magnetic suspension system that places control plates beside the magnetic source (permanent magnet) is proposed. In a conventional flux-path control magnetic suspension system, the control plates were inserted between the magnetic source and the suspended object (floator). In contrast, [...] Read more.
A novel flux control magnetic suspension system that places control plates beside the magnetic source (permanent magnet) is proposed. In a conventional flux-path control magnetic suspension system, the control plates were inserted between the magnetic source and the suspended object (floator). In contrast, the control plates were placed beside the magnetic source in the proposed system. In such a configuration, the effective gap becomes larger than in the conventional system. Basic characteristics of the proposed magnetic suspension system were studied both numerically and experimentally. The numerical analyses show that the attractive force acting on the floator increases as the position of the lateral ring-shape control plate increases. The variation of the attractive force is sufficient for the stabilization of the suspension system. It is also shown that lateral force can be generated by dividing the plates into halves and moving them differentially. The predicted characteristics are confirmed experimentally in a fabricated apparatus with a three-axis force sensor and a gap adjustment mechanism. Full article
(This article belongs to the Special Issue Active Magnetic Bearing Actuators)
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5145 KiB  
Article
Design, Implementation and Evaluation of a Pump-Controlled Circuit for Single Rod Actuators
by Ahmed Imam, Moosa Rafiq, Ehsan Jalayeri and Nariman Sepehri
Actuators 2017, 6(1), 10; https://doi.org/10.3390/act6010010 - 20 Feb 2017
Cited by 27 | Viewed by 9256
Abstract
Pump-controlled hydraulic circuits are more efficient than valve-controlled circuits, as they eliminate the energy losses due to flow throttling in valves and require less cooling effort. Presently existing pump-controlled solutions for single rod cylinders encounter an undesirable performance during certain operating conditions. This [...] Read more.
Pump-controlled hydraulic circuits are more efficient than valve-controlled circuits, as they eliminate the energy losses due to flow throttling in valves and require less cooling effort. Presently existing pump-controlled solutions for single rod cylinders encounter an undesirable performance during certain operating conditions. This paper investigates the performance issues in common pump-controlled circuits for the single rod actuators. Detailed analysis is conducted that identifies these regions in a load-velocity plane and the factors affecting them. The findings are validated by experimental results. A new design is then proposed that employs a limited throttling valve alongside two pilot operated check valves for differential flow compensation to improve the performance. The valve is of the flow control type and is chosen to have a throttling effect over critical regions; it has the least throttling over other operating regions, thus maintaining efficiency. Experimental work demonstrates improved performance in a full operating range of the actuator as compared to a circuit that uses only the pilot-operated check valves. This circuit is energy efficient and capable of recuperating energy. Full article
(This article belongs to the Special Issue Hydraulic Actuators)
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2119 KiB  
Article
Transpermeance Amplifier Applied to Magnetic Bearings
by Jossana Ferreira, Eric Maslen and Roger Fittro
Actuators 2017, 6(1), 9; https://doi.org/10.3390/act6010009 - 15 Feb 2017
Cited by 8 | Viewed by 7489
Abstract
The most conventional approach of controlling magnetic forces in active magnetic bearings (AMBs) is through current feedback amplifiers: transconductance. This enables the operation of the AMB to be understood in terms of a relatively simple current-based model as has been widely reported on [...] Read more.
The most conventional approach of controlling magnetic forces in active magnetic bearings (AMBs) is through current feedback amplifiers: transconductance. This enables the operation of the AMB to be understood in terms of a relatively simple current-based model as has been widely reported on in the literature. The alternative notion of using transpermeance amplifiers, which approximate the feedback of gap flux rather than current, has been in commercial use in some form for at least thirty years, however is only recently seeing more widespread acceptance as a commercial standard. This study explores how such alternative amplifiers should be modeled and then examines the differences in behavior between AMBs equipped with transconductance and transpermeance amplifiers. The focus of this study is on two aspects. The first is the influence of rotor displacement on AMB force, commonly modeled as a constant negative equivalent mechanical stiffness, and it is shown that either scheme actually leads to a finite bandwidth effect, but that this bandwidth is much lower when transpermeance is employed. The second aspect is the influence of eddy currents. Using a very simple model of eddy currents (a secondary short-circuited coil), it is demonstrated that transpermeance amplifiers can recover significant actuator bandwidth compared with transconductance, but at the cost of needing increased peak current headroom. Full article
(This article belongs to the Special Issue Active Magnetic Bearing Actuators)
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1128 KiB  
Review
Piezoelectric Inertia Motors—A Critical Review of History, Concepts, Design, Applications, and Perspectives
by Matthias Hunstig
Actuators 2017, 6(1), 7; https://doi.org/10.3390/act6010007 - 06 Feb 2017
Cited by 105 | Viewed by 15070
Abstract
Piezoelectric inertia motors—also known as stick-slip motors or (smooth) impact drives—use the inertia of a body to drive it in small steps by means of an uninterrupted friction contact. In addition to the typical advantages of piezoelectric motors, they are especially suited for [...] Read more.
Piezoelectric inertia motors—also known as stick-slip motors or (smooth) impact drives—use the inertia of a body to drive it in small steps by means of an uninterrupted friction contact. In addition to the typical advantages of piezoelectric motors, they are especially suited for miniaturisation due to their simple structure and inherent fine-positioning capability. Originally developed for positioning in microscopy in the 1980s, they have nowadays also found application in mass-produced consumer goods. Recent research results are likely to enable more applications of piezoelectric inertia motors in the future. This contribution gives a critical overview of their historical development, functional principles, and related terminology. The most relevant aspects regarding their design—i.e., friction contact, solid state actuator, and electrical excitation—are discussed, including aspects of control and simulation. The article closes with an outlook on possible future developments and research perspectives. Full article
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1335 KiB  
Article
Applying Standard Industrial Components for Active Magnetic Bearings
by Bert-Uwe Koehler, Joachim Denk, Gijs Van Maanen and Matthias Lang
Actuators 2017, 6(1), 8; https://doi.org/10.3390/act6010008 - 04 Feb 2017
Cited by 8 | Viewed by 8747
Abstract
With the increasing number of active magnetic bearing applications, satisfying additional requirements is becoming increasingly more important. As for every technology, moving away from being a niche product and achieving a higher level of maturity, these requirements relate to robustness, reliability, availability, safety, [...] Read more.
With the increasing number of active magnetic bearing applications, satisfying additional requirements is becoming increasingly more important. As for every technology, moving away from being a niche product and achieving a higher level of maturity, these requirements relate to robustness, reliability, availability, safety, security, traceability, certification, handling, flexibility, reporting, costs, and delivery times. Employing standard industrial components, such as those from flexible modular motion control drive systems, is an approach that allows these requirements to be satisfied while achieving rapid technological innovation. In this article, we discuss technical and non-technical aspects of using standard industrial components in magnetic bearing applications. Full article
(This article belongs to the Special Issue Active Magnetic Bearing Actuators)
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818 KiB  
Article
A Miniature Pneumatic Bending Rubber Actuator Controlled by Using the PSO-SVR-Based Motion Estimation Method with the Generalized Gaussian Kernel
by Kou Fujita, Mingcong Deng and Shuichi Wakimoto
Actuators 2017, 6(1), 6; https://doi.org/10.3390/act6010006 - 03 Feb 2017
Cited by 23 | Viewed by 7419
Abstract
Soft actuators have been employed in various fields recently. A miniature pneumatic bending rubber actuator is one of the soft actuators. This actuator will be used for medical and biological fields. Its flexibility and high safety are suitable for fragile objects. However, its [...] Read more.
Soft actuators have been employed in various fields recently. A miniature pneumatic bending rubber actuator is one of the soft actuators. This actuator will be used for medical and biological fields. Its flexibility and high safety are suitable for fragile objects. However, its modeling is difficult due to its nonlinearity. There are no suitable sensors to measure the output of this actuator. In this paper, the particle swarm optimization-support vector regression (PSO-SVR)-based estimation method with the generalized Gaussian kernel is proposed. An experimental result with the operator-based robust nonlinear control system is employed to verify the effectiveness of the proposed method. Full article
(This article belongs to the Special Issue MEMS-based Actuators)
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4018 KiB  
Article
Re-Engineering a High Performance Electrical Series Elastic Actuator for Low-Cost Industrial Applications
by Kenan Isik, Shunde He, Joseph Ho and Luis Sentis
Actuators 2017, 6(1), 5; https://doi.org/10.3390/act6010005 - 22 Jan 2017
Cited by 12 | Viewed by 11579
Abstract
Cost is an important consideration when transferring a technology from research to industrial and educational use. In this paper, we introduce the design of an industrial grade series elastic actuator (SEA) performed via re-engineering a research grade version of it. Cost-constrained design requires [...] Read more.
Cost is an important consideration when transferring a technology from research to industrial and educational use. In this paper, we introduce the design of an industrial grade series elastic actuator (SEA) performed via re-engineering a research grade version of it. Cost-constrained design requires careful consideration of the key performance parameters for an optimal performance-to-cost component selection. To optimize the performance of the new design, we started by matching the capabilities of a high-performance SEA while cutting down its production cost significantly. Our posit was that performing a re-engineering design process on an existing high-end device will significantly reduce the cost without compromising the performance drastically. As a case study of design for manufacturability, we selected the University of Texas Series Elastic Actuator (UT-SEA), a high-performance SEA, for its high power density, compact design, high efficiency and high speed properties. We partnered with an industrial corporation in China to research the best pricing options and to exploit the retail and production facilities provided by the Shenzhen region. We succeeded in producing a low-cost industrial grade actuator at one-third of the cost of the original device by re-engineering the UT-SEA with commercial off-the-shelf components and reducing the number of custom-made parts. Subsequently, we conducted performance tests to demonstrate that the re-engineered product achieves the same high-performance specifications found in the original device. With this paper, we aim to raise awareness in the robotics community on the possibility of low-cost realization of low-volume, high performance, industrial grade research and education hardware. Full article
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4052 KiB  
Article
Fractional Order PID Control of Rotor Suspension by Active Magnetic Bearings
by Parinya Anantachaisilp and Zongli Lin
Actuators 2017, 6(1), 4; https://doi.org/10.3390/act6010004 - 13 Jan 2017
Cited by 37 | Viewed by 12628
Abstract
One of the key issues in control design for Active Magnetic Bearing (AMB) systems is the tradeoff between the simplicity of the controller structure and the performance of the closed-loop system. To achieve this tradeoff, this paper proposes the design of a fractional [...] Read more.
One of the key issues in control design for Active Magnetic Bearing (AMB) systems is the tradeoff between the simplicity of the controller structure and the performance of the closed-loop system. To achieve this tradeoff, this paper proposes the design of a fractional order Proportional-Integral-Derivative (FOPID) controller. The FOPID controller consists of only two additional parameters in comparison with a conventional PID controller. The feasibility of FOPID for AMB systems is investigated for rotor suspension in both the radial and axial directions. Tuning methods are developed based on the evolutionary algorithms for searching the optimal values of the controller parameters. The resulting FOPID controllers are then tested and compared with a conventional PID controller, as well as with some advanced controllers such as Linear Quadratic Gausian (LQG) and H controllers. The comparison is made in terms of various stability and robustness specifications, as well as the dimensions of the controllers as implemented. Lastly, to validate the proposed method, experimental testing is carried out on a single-stage centrifugal compressor test rig equipped with magnetic bearings. The results show that, with a proper selection of gains and fractional orders, the performance of the resulting FOPID is similar to those of the advanced controllers. Full article
(This article belongs to the Special Issue Active Magnetic Bearing Actuators)
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165 KiB  
Editorial
Acknowledgement to Reviewers of Actuators in 2016
by Actuators Editorial Office
Actuators 2017, 6(1), 3; https://doi.org/10.3390/act6010003 - 11 Jan 2017
Cited by 68 | Viewed by 5243
Abstract
The editors of Actuators would like to express their sincere gratitude to the following reviewers for assessing manuscripts in 2016.[...] Full article
2354 KiB  
Article
Active Magnetic Bearing Online Levitation Recovery through μ-Synthesis Robust Control
by Alexander H. Pesch and Jerzy T. Sawicki
Actuators 2017, 6(1), 2; https://doi.org/10.3390/act6010002 - 08 Jan 2017
Cited by 22 | Viewed by 8312
Abstract
A rotor supported on active magnetic bearings (AMBs) is levitated inside an air gap by electromagnets controlled in feedback. In the event of momentary loss of levitation due to an acute exogenous disturbance or external fault, reestablishing levitation may be prevented by unbalanced [...] Read more.
A rotor supported on active magnetic bearings (AMBs) is levitated inside an air gap by electromagnets controlled in feedback. In the event of momentary loss of levitation due to an acute exogenous disturbance or external fault, reestablishing levitation may be prevented by unbalanced forces, contact forces, and the rotor’s dynamics. A novel robust control strategy is proposed for ensuring levitation recovery. The proposed strategy utilizes model-based μ-synthesis to find the requisite AMB control law with unique provisions to account for the contact forces and to prevent control effort saturation at the large deflections that occur during levitation failure. The proposed strategy is demonstrated experimentally with an AMB test rig. First, rotor drop tests are performed to tune a simple touchdown-bearing model. That model is then used to identify a performance weight, which bounds the contact forces during controller synthesis. Then, levitation recovery trials are conducted at 1000 and 2000 RPM, in which current to the AMB coils is momentarily stopped, representing an external fault. The motor is allowed to drive the rotor on the touchdown bearings until coil current is restored. For both cases, the proposed control strategy shows a marked improvement in relevitation transients. Full article
(This article belongs to the Special Issue Active Magnetic Bearing Actuators)
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461 KiB  
Article
A Generalized Unbiased Control Strategy for Radial Magnetic Bearings
by David Meeker
Actuators 2017, 6(1), 1; https://doi.org/10.3390/act6010001 - 08 Jan 2017
Cited by 13 | Viewed by 7509
Abstract
The present work extends a method of unbiased control originally developed for three-pole radial magnetic bearings into a generalized unbiased control strategy that encompasses bearings with an arbitrary number of poles. By allowing the control of bearings with more than three poles, the [...] Read more.
The present work extends a method of unbiased control originally developed for three-pole radial magnetic bearings into a generalized unbiased control strategy that encompasses bearings with an arbitrary number of poles. By allowing the control of bearings with more than three poles, the applicability of the approach is broadened to the case of large rotors. Other ramifications of this generalized unbiased control strategy are fault tolerant unbiased bearings, control of bearings with more than three poles using 3-phase drives, and a novel approach to the unbiased control of eight-pole magnetic bearings. Full article
(This article belongs to the Special Issue Active Magnetic Bearing Actuators)
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