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Machines, Volume 2, Issue 4 (December 2014) – 6 articles , Pages 219-324

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521 KiB

Open AccessArticle

Contactless Mechanical Components: Gears, Torque Limiters and Bearings

by Jose Luis Perez-Diaz, Efren Diez-Jimenez, Ignacio Valiente-Blanco, Cristian Cristache, Marco-Antonio Alvarez-Valenzuela and Juan Sanchez-Garcia-Casarrubios

Machines 2014, 2(4), 312-324; https://doi.org/10.3390/machines2040312 - 18 Dec 2014

Cited by 12 | Viewed by 9693

Abstract

Contactless mechanical components are mechanical sets for conversion of torque/speed, whose gears and moving parts do not touch each other, but rather they provide movement with magnets and magnetic materials that exert force from a certain distance. Magneto-mechanical transmission devices have several advantages over conventional mechanisms: no friction between rotatory elements (no power losses or heat generation by friction so increase of efficiency), no lubrication is needed (oil-free mechanisms and no lubrication auxiliary systems), reduced maintenance (no lubricant so no need of oil replacements), wider operational temperature ranges (no lubricant evaporation or freezing), overload protection (if overload occurs magnet simply slides but no teeth brake), through-wall connection (decoupling of thermal and electrical paths and environmental isolation), larger operative speeds (more efficient operative conditions), ultralow noise and vibrations (no contact no noise generation). All these advantages permit us to foresee in the long term several common industrial applications in which including contactless technology would mean a significant breakthrough for their performance. In this work, we present three configurations of contactless mechanical passive components: magnetic gears, magnetic torque limiters and superconducting magnetic bearings. We summarize the main characteristic and range of applications for each type; we show experimental results of the most recent developments showing their performance. Full article

(This article belongs to the Special Issue Feature Papers)

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810 KiB

Open AccessArticle

Extrusion Roller Imprinting with a Variotherm Belt Mold

by Raymond Frenkel, Byung Kim and Donggang Yao

Machines 2014, 2(4), 299-311; https://doi.org/10.3390/machines2040299 - 18 Dec 2014

Cited by 8 | Viewed by 8119

Abstract

Although many precision fabrication techniques have demonstrated the ability to produce microstructures and micro-devices with sub 100 nm accuracy, we are yet to see a scalable manufacturing process for large-area production. One promising solution to scalable micro- and nanofabrication is thermal roller imprinting. However, existing investigations on thermal roller imprinting revealed poor pattern transfer fidelity, especially for high aspect ratio features. The standard roller imprinting process suffers from the lack of an effective holding and cooling stage so that the adverse effects from the viscoelastic nature of polymers are not managed. To rectify this problem and further improve the production rate, a new extrusion roller imprinting process with a variotherm belt mold is designed, and its prototype was established at a laboratory scale. The process testing results demonstrate that a 30 μm sawtooth pattern can be faithfully transferred to extruded polyethylene film at take-up speeds higher than 10 m/min. The results are promising in that microfeatures or even nanofeatures may be successfully replicated by a robust and scalable industrial process suitable for large-area, continuous production. Full article

(This article belongs to the Special Issue Advances and Challenges in Manufacturing Automation)

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519 KiB

Open AccessArticle

Residual Generator Fuzzy Identification for Wind TurbineBenchmark Fault Diagnosis

by Silvio Simani, Saverio Farsoni and Paolo Castaldi

Machines 2014, 2(4), 275-298; https://doi.org/10.3390/machines2040275 - 27 Nov 2014

Cited by 10 | Viewed by 4777

Abstract

In order to improve the availability of wind turbines, thus improving theirefficiency, it is important to detect and isolate faults in their earlier occurrence. The mainproblem of model-based fault diagnosis applied to wind turbines is represented by thesystem complexity, as well as the reliability of the available measurements. In this work, adata-driven strategy relying on fuzzy models is presented, in order to build a fault diagnosissystem. Fuzzy theory jointly with the Frisch identification scheme for errors-in-variablemodels is exploited here, since it allows one to approximate unknown models and manageuncertain data. Moreover, the use of fuzzy models, which are directly identified from thewind turbine measurements, allows the design of the fault detection and isolation module.It is worth noting that, sometimes, the nonlinearity of a wind turbine system could lead toquite complex analytic solutions. However, IF-THEN fuzzy rules provide a simpler solution,important when on-line implementations have to be considered. The wind turbine benchmarkis used to validate the achieved performances of the suggested fault detection and isolationscheme. Finally, comparisons of the proposed methodology with respect to different faultdiagnosis methods serve to highlight the features of the suggested solution. Full article

(This article belongs to the Special Issue Machinery Diagnostics and Prognostics)

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1464 KiB

Open AccessArticle

Data-Driven Methods for the Detection of Causal Structures in Process Technology

by Christian Kühnert and Jürgen Beyerer

Machines 2014, 2(4), 255-274; https://doi.org/10.3390/machines2040255 - 04 Nov 2014

Cited by 14 | Viewed by 4544

Abstract

In modern industrial plants, process units are strongly cross-linked with eachother, and disturbances occurring in one unit potentially become plant-wide. This can leadto a flood of alarms at the supervisory control and data acquisition system, hiding the originalfault causing the disturbance. Hence, one major aim in fault diagnosis is to backtrackthe disturbance propagation path of the disturbance and to localize the root cause of thefault. Since detecting correlation in the data is not sufficient to describe the direction of thepropagation path, cause-effect dependencies among process variables need to be detected.Process variables that show a strong causal impact on other variables in the process comeinto consideration as being the root cause. In this paper, different data-driven methods areproposed, compared and combined that can detect causal relationships in data while solelyrelying on process data. The information of causal dependencies is used for localization ofthe root cause of a fault. All proposed methods consist of a statistical part, which determineswhether the disturbance traveling from one process variable to a second is significant, and aquantitative part, which calculates the causal information the first process variable has aboutthe second. The methods are tested on simulated data from a chemical stirred-tank reactorand on a laboratory plant. Full article

(This article belongs to the Special Issue Machinery Diagnostics and Prognostics)

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231 KiB

Open AccessArticle

Performance Evaluation of Bidding-Based Multi-Agent Scheduling Algorithms for Manufacturing Systems

by Antonio Gordillo and Adriana Giret

Machines 2014, 2(4), 233-254; https://doi.org/10.3390/machines2040233 - 31 Oct 2014

Cited by 7 | Viewed by 5807

Abstract

Artificial Intelligence techniques have being applied to many problems in manufacturing systems in recent years. In the specific field of manufacturing scheduling many studies have been published trying to cope with the complexity of the manufacturing environment. One of the most utilized approaches is (multi) agent-based scheduling. Nevertheless, despite the large list of studies reported in this field, there is no resource or scientific study on the performance measure of this type of approach under very common and critical execution situations. This paper focuses on multi-agent systems (MAS) based algorithms for task allocation, particularly in manufacturing applications. The goal is to provide a mechanism to measure the performance of agent-based scheduling approaches for manufacturing systems under key critical situations such as: dynamic environment, rescheduling, and priority change. With this mechanism it will be possible to simulate critical situations and to stress the system in order to measure the performance of a given agent-based scheduling method. The proposed mechanism is a pioneering approach for performance evaluation of bidding-based MAS approaches for manufacturing scheduling. The proposed method and evaluation methodology can be used to run tests in different manufacturing floors since it is independent of the workshop configuration. Moreover, the evaluation results presented in this paper show the key factors and scenarios that most affect the market-like MAS approaches for manufacturing scheduling. Full article

(This article belongs to the Special Issue Advances and Challenges in Manufacturing Automation)

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588 KiB

Open AccessArticle

Robotized Surface Mounting of Permanent Magnets

by Erik Hultman, Dana Salar and Mats Leijon

Machines 2014, 2(4), 219-232; https://doi.org/10.3390/machines2040219 - 22 Oct 2014

Cited by 10 | Viewed by 7791

Abstract

Using permanent magnets on a rotor can both simplify the design and increase the efficiency of electric machines compared to using electromagnets. A drawback, however, is the lack of existing automated assembly methods for large machines. This paper presents and motivates a method for robotized surface mounting of permanent magnets on electric machine rotors. The translator of the Uppsala University Wave Energy Converter generator is used as an example of a rotor. The robot cell layout, equipment design and assembly process are presented and validated through computer simulations and experiments with prototype equipment. A comparison with manual assembly indicates substantial cost savings and an improved work environment. By using the flexibility of industrial robots and a scalable equipment design, it is possible for this assembly method to be adjusted for other rotor geometries and sizes. Finally, there is a discussion on the work that remains to be done on improving and integrating the robot cell into a production line. Full article

(This article belongs to the Special Issue Advances and Challenges in Manufacturing Automation)

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