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Machines, Volume 5, Issue 1 (March 2017)

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Editorial

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Open AccessEditorial Acknowledgement to Reviewers of Machines in 2016
Machines 2017, 5(1), 2; doi:10.3390/machines5010002
Received: 10 January 2017 / Revised: 10 January 2017 / Accepted: 10 January 2017 / Published: 10 January 2017
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Abstract
The editors of Machines would like to express their sincere gratitude to the following reviewers for assessing manuscripts in 2016.[...] Full article

Research

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Open AccessArticle Online Estimation and Correction of Systematic Encoder Line Errors
Machines 2017, 5(1), 1; doi:10.3390/machines5010001
Received: 16 November 2016 / Revised: 29 December 2016 / Accepted: 1 January 2017 / Published: 6 January 2017
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Abstract
This paper addresses the identification and correction of amplitude and offset errors in the sinusoidal outputs from incremental position encoders. Precise angular position measurement is of high importance in many position control applications. Manufacturing tolerances and noise from thermal and electromagnetic interference sources
[...] Read more.
This paper addresses the identification and correction of amplitude and offset errors in the sinusoidal outputs from incremental position encoders. Precise angular position measurement is of high importance in many position control applications. Manufacturing tolerances and noise from thermal and electromagnetic interference sources introduce systematic and random errors in the orthogonal sine cosine output line signals. Evaluation of these signals reproduces deviations in the measured angular position. This paper proposes two methods to identify and compensate for the influence of the systematic errors online without the necessity of a reference measurement during identification. The key component of the methods is a nonlinear estimator that exploits the orthogonality property of harmonic functions. The first method explains the basic idea with a scalar error model and operates continuously but exhibits an angular shift in direction of rotation during transients of the parameters, whereas the second method assumes an error model with error parameters as a function over one full revolution of the encoder. The latter updates the error function iteratively in subsequent revolutions. Full article
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Open AccessArticle Automatic Motion Generation for Robotic Milling Optimizing Stiffness with Sample-Based Planning
Machines 2017, 5(1), 3; doi:10.3390/machines5010003
Received: 1 November 2016 / Revised: 20 December 2016 / Accepted: 9 January 2017 / Published: 18 January 2017
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Abstract
Optimal and intuitive robotic machining is still a challenge. One of the main reasons for this is the lack of robot stiffness, which is also dependent on the robot positioning in the Cartesian space. To make up for this deficiency and with the
[...] Read more.
Optimal and intuitive robotic machining is still a challenge. One of the main reasons for this is the lack of robot stiffness, which is also dependent on the robot positioning in the Cartesian space. To make up for this deficiency and with the aim of increasing robot machining accuracy, this contribution describes a solution approach for optimizing the stiffness over a desired milling path using the free degree of freedom of the machining process. The optimal motion is computed based on the semantic and mathematical interpretation of the manufacturing process modeled on its components: product, process and resource; and by configuring automatically a sample-based motion problem and the transition-based rapid-random tree algorithm for computing an optimal motion. The approach is simulated on a CAM software for a machining path revealing its functionality and outlining future potentials for the optimal motion generation for robotic machining processes. Full article
(This article belongs to the Special Issue Robotic Machine Tools)
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Open AccessArticle Physics-Embedded Machine Learning: Case Study with Electrochemical Micro-Machining
Machines 2017, 5(1), 4; doi:10.3390/machines5010004
Received: 29 October 2016 / Revised: 11 December 2016 / Accepted: 11 January 2017 / Published: 17 January 2017
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Abstract
Although intelligent machine learning techniques have been used for input-output modeling of many different manufacturing processes, these techniques map directly from the input process parameters to the outputs and do not take into consideration any partial knowledge available about the mechanisms and physics
[...] Read more.
Although intelligent machine learning techniques have been used for input-output modeling of many different manufacturing processes, these techniques map directly from the input process parameters to the outputs and do not take into consideration any partial knowledge available about the mechanisms and physics of the process. In this paper, a new approach is presented for taking advantage of the partial knowledge available about the mechanisms of the process and embedding it into the neural network structure. To validate the proposed approach, it is used to create a forward prediction model for the process of electrochemical micro-machining (μ-ECM). The prediction accuracy of the proposed approach is compared to the prediction accuracy of pure neural structure models with different structures and the results show that the Neural Network (NN) models with embedded knowledge have better prediction accuracy over pure NN models. Full article
(This article belongs to the Special Issue Precision Manufacturing Processes)
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Open AccessArticle A Method for Design of Modular Reconfigurable Machine Tools
Machines 2017, 5(1), 5; doi:10.3390/machines5010005
Received: 10 November 2016 / Revised: 13 January 2017 / Accepted: 23 January 2017 / Published: 4 February 2017
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Abstract
Presented in this paper is a method for the design of modular reconfigurable machine tools (MRMTs). An MRMT is capable of using a minimal number of modules through reconfiguration to perform the required machining tasks for a family of parts. The proposed method
[...] Read more.
Presented in this paper is a method for the design of modular reconfigurable machine tools (MRMTs). An MRMT is capable of using a minimal number of modules through reconfiguration to perform the required machining tasks for a family of parts. The proposed method consists of three steps: module identification, module determination, and layout synthesis. In the first step, the module components are collected from a family of general-purpose machines to establish a module library. In the second step, for a given family of parts to be machined, a set of needed modules are selected from the module library to construct a desired reconfigurable machine tool. In the third step, a final machine layout is decided though evaluation by considering a number of performance indices. Based on this method, a software package has been developed that can design an MRMT for a given part family. Full article
(This article belongs to the Special Issue Robotic Machine Tools)
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Open AccessArticle Perception, Planning, Control, and Coordination for Autonomous Vehicles
Machines 2017, 5(1), 6; doi:10.3390/machines5010006
Received: 3 January 2017 / Revised: 1 February 2017 / Accepted: 13 February 2017 / Published: 17 February 2017
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Abstract
Autonomous vehicles are expected to play a key role in the future of urban transportation systems, as they offer potential for additional safety, increased productivity, greater accessibility, better road efficiency, and positive impact on the environment. Research in autonomous systems has seen dramatic
[...] Read more.
Autonomous vehicles are expected to play a key role in the future of urban transportation systems, as they offer potential for additional safety, increased productivity, greater accessibility, better road efficiency, and positive impact on the environment. Research in autonomous systems has seen dramatic advances in recent years, due to the increases in available computing power and reduced cost in sensing and computing technologies, resulting in maturing technological readiness level of fully autonomous vehicles. The objective of this paper is to provide a general overview of the recent developments in the realm of autonomous vehicle software systems. Fundamental components of autonomous vehicle software are reviewed, and recent developments in each area are discussed. Full article
(This article belongs to the Special Issue Mechatronics: Intelligent Machines)
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Open AccessArticle Life Cycle Analysis of Double-Arm Type Robotic Tools for LCD Panel Handling
Machines 2017, 5(1), 8; doi:10.3390/machines5010008
Received: 31 December 2016 / Revised: 1 March 2017 / Accepted: 2 March 2017 / Published: 4 March 2017
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Abstract
This study includes a life cycle assessment of double-arm type robotic tools made with three different materials. The robotic arms are used for Liquid Crystal Display (LCD) panel handling. The environmental impacts generated during all the life stages of the robots have been
[...] Read more.
This study includes a life cycle assessment of double-arm type robotic tools made with three different materials. The robotic arms are used for Liquid Crystal Display (LCD) panel handling. The environmental impacts generated during all the life stages of the robots have been investigated. The study shows that composite materials have less environmental impact compared with metallic materials. It is also found that the most significant impact category generated by the robotic tools is carcinogen, while the use stage of the robotic tool’s life cycle has the greatest environmental impact. Full article
(This article belongs to the Special Issue Robotic Machine Tools)
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Open AccessArticle Direct Uncertainty Minimization Framework for System Performance Improvement in Model Reference Adaptive Control
Machines 2017, 5(1), 9; doi:10.3390/machines5010009
Received: 3 January 2017 / Accepted: 28 February 2017 / Published: 8 March 2017
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Abstract
Inthispaper, adirectuncertaintyminimizationframeworkisdevelopedanddemonstrated for model reference adaptive control laws. The proposed framework consists of a novel architecture involvingmodificationtermsintheadaptivecontrollawandtheupdatelaw. Inparticular,theseterms areconstructedthroughagradientminimizationprocedureinordertoachieveimprovedclosed-loop system performance with adaptive control laws. The proposed framework is first developed for adaptive control laws with linear reference models and then generalized to
[...] Read more.
Inthispaper, adirectuncertaintyminimizationframeworkisdevelopedanddemonstrated for model reference adaptive control laws. The proposed framework consists of a novel architecture involvingmodificationtermsintheadaptivecontrollawandtheupdatelaw. Inparticular,theseterms areconstructedthroughagradientminimizationprocedureinordertoachieveimprovedclosed-loop system performance with adaptive control laws. The proposed framework is first developed for adaptive control laws with linear reference models and then generalized to adaptive control laws with nonlinear reference models. Two illustrative numerical examples are included to demonstrate the efficacy of the proposed framework. Full article
(This article belongs to the Special Issue Robotic Machine Tools)
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Open AccessArticle Automated Mounting of Pole-Shoe Wedges in Linear Wave Power Generators—Using Industrial Robotics and Proximity Sensors
Machines 2017, 5(1), 10; doi:10.3390/machines5010010
Received: 16 January 2017 / Revised: 8 March 2017 / Accepted: 10 March 2017 / Published: 17 March 2017
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Abstract
A system for automatic mounting of high tolerance wedges inside a wave power linear generator is proposed. As for any renewable energy concept utilising numerous smaller generation units, minimising the production cost per unit is vital for commercialization. The linear generator in question
[...] Read more.
A system for automatic mounting of high tolerance wedges inside a wave power linear generator is proposed. As for any renewable energy concept utilising numerous smaller generation units, minimising the production cost per unit is vital for commercialization. The linear generator in question uses self-locking wedges, which are challenging to mount using industrial robots due to the high tolerances used, and because of the fact that any angular error remaining after calibration risks damaging the equipment. Using two types of probes, mechanical touch probes and inductive proximity sensors, combined with a flexible robot tool and iterative calibration routines, an automatic mounting system that overcomes the challenges of high tolerance wedge mounting is presented. The system is experimentally verified to work at mounting speeds of up to 50mm/s, and calibration accuracies of 0.25mmand 0.1 ∘ are achieved. The use of a flexible robot tool, able to move freely in one Cartesian plane, was found to be essential for making the system work. Full article
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Review

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Open AccessReview The Insulation for Machines Having a High Lifespan Expectancy, Design, Tests and Acceptance Criteria Issues
Machines 2017, 5(1), 7; doi:10.3390/machines5010007
Received: 9 September 2016 / Revised: 19 November 2016 / Accepted: 26 November 2016 / Published: 20 February 2017
Cited by 1 | PDF Full-text (11104 KB) | HTML Full-text | XML Full-text
Abstract
The windings insulation of electrical machines will remain a topic that is updated frequently. The criteria severity requested by the electrical machine applications increases continuously. Manufacturers and designers are always confronted with new requirements or new criteria with enhanced performances. The most problematic
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The windings insulation of electrical machines will remain a topic that is updated frequently. The criteria severity requested by the electrical machine applications increases continuously. Manufacturers and designers are always confronted with new requirements or new criteria with enhanced performances. The most problematic requirements that will be investigated here are the extremely long lifespan coupled to critical operating conditions (overload, supply grid instabilities, and critical operating environments). Increasing lifespan does not have a considerable benefit because the purchasing price of usual machines has to be compared to the purchasing price and maintenance price of long lifespan machines. A machine having a 40-year lifespan will cost more than twice the usual price of a 20-year lifetime machine. Systems which need a long lifetime are systems which are crucial for a country, and those for which outage costs are exorbitant. Nuclear power stations are such systems. It is certain that the used technologies have evolved since the first nuclear power plant, but they cannot evolve as quickly as in other sectors of activities. No-one wants to use an immature technology in such power plants. Even if the electrical machines have exceeded 100 years of age, their improvements are linked to a patient and continuous work. Nowadays, the windings insulation systems have a well-established structure, especially high voltage windings. Unfortunately, a high life span is not only linked to this result. Several manufacturers’ improvements induced by many years of experiment have led to the writing of standards that help the customers and the manufacturers to regularly enhance the insulation specifications or qualifications. Hence, in this publication, the authors will give a step by step exhaustive review of one insulation layout and will take time to give a detailed report on the standards that are linked to insulation systems. No standard can provide insurance about lifespan, nor do any insulation tests incorporate all of the operating conditions: thermal, mechanical, moisture and chemical. Even if one manufacturer uses the standards compliance to demonstrate the quality of its realization; in the end, the successful use in operation remains an objective test. Thereafter, both customer and manufacturers will use the standards while knowing that such documents cannot fully satisfy their wishes. In one 20-year historical review, the authors will highlight the duration in insulation improvements and small breakthroughs in standards writing. High lifespan machines are not the main interest of standards. A large part of this publication is dedicated to the improvements of the insulation wall to achieve the lifespan. Even if the choice of raw materials is fundamental, the understanding of ageing phenomena also leads to improvements. Full article
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