Open AccessArticle
Optimization of Microchannel Heat Sinks Using Prey-Predator Algorithm and Artificial Neural Networks
Machines 2018, 6(2), 26; https://doi.org/10.3390/machines6020026 -
Abstract
A rectangular microchannel heat sink is modeled by employing thermal resistance and pressure drop networks. The available correlations for both thermal resistance and pressure drop are utilized in optimization. A multi-objective optimization technique, the prey–predator algorithm, is employed with the objective to find
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A rectangular microchannel heat sink is modeled by employing thermal resistance and pressure drop networks. The available correlations for both thermal resistance and pressure drop are utilized in optimization. A multi-objective optimization technique, the prey–predator algorithm, is employed with the objective to find the optimal values for the heat sink performance parameters, i.e., thermal resistance and the pumping power of the heat sink. Additionally, a radial basis function neural network is used to investigate a relationship between these parameters. Full training based on the prey–predator algorithm with the sum of the squared error function is used to achieve the best performance of the model. The analysis of variance method is also employed to test the performance of this model. This study shows that the multi-objective function based on the prey–predator algorithm and the neural networks is suitable for finding the optimal values for the microchannel heat sink parameters. The minimum values of the multi-objective function are found to be “pumping power = 2.79344” and “total thermal resistance = 0.134133”. Full article
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Open AccessArticle
Monitoring the Oil of Wind-Turbine Gearboxes: Main Degradation Indicators and Detection Methods
Machines 2018, 6(2), 25; https://doi.org/10.3390/machines6020025 -
Abstract
Oil condition monitoring is a common practice in the wind industry. However, the published research about oil degradation in wind turbine gearboxes is limited. This paper aims at providing new information on the oil degradation process by analyzing wind turbine gearbox oils aged
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Oil condition monitoring is a common practice in the wind industry. However, the published research about oil degradation in wind turbine gearboxes is limited. This paper aims at providing new information on the oil degradation process by analyzing wind turbine gearbox oils aged in the laboratory and in the field. Oil samples were analyzed in the laboratory and two sensors were used to determine the oil condition by means of dielectric constant and conductivity measurements. Additionally, micropitting tests were carried out for three oils with different base stocks. The results of this study show that viscosity changes of the oils from the field were not significant.Extreme pressure additives depletion and the increase of the iron content are among the most relevant degradation indicators. The oil sensors used in this study provided limited information on the oil degradation process. The accuracy of the sensors was affected by the oil type and its measurement range. The results of the micropitting tests showed that even aged oils exhibited a high micropitting resistance. Full article
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Open AccessArticle
Prediction of Thrust Force and Cutting Torque in Drilling Based on the Response Surface Methodology
Machines 2018, 6(2), 24; https://doi.org/10.3390/machines6020024 -
Abstract
In this research, experimental studies were based on drilling with solid carbide tools and the material used was Al7075. The study primarily focused on investigating the effects of machining parameters (cutting speed, feed rate, diameter of the tool) on the thrust force (
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In this research, experimental studies were based on drilling with solid carbide tools and the material used was Al7075. The study primarily focused on investigating the effects of machining parameters (cutting speed, feed rate, diameter of the tool) on the thrust force (Fz) and the cutting torque (Mz) when drilling an Al7075 workpiece. The experimental data were analyzed using the response surface methodology (RSM) with an aim to identify the significant factors on the development of both the Fz and Mz. The application of the mathematical models provided favorable results with an accuracy of 3.4% and 4.7%, for the Fz and the Mz, respectively. Analysis of variance (ANOVA) was applied in order to examine the effectiveness of the model, and both mathematical models were established and validated. The equations derived proved to be very precise when a set of validation tests were executed. The importance of the factors’ influence over the responses was also presented. Both the diameter of the cutting and the feed rate were found to be the factors of high significance, while cutting speed did not affect considerably the Fz and Mz in the experiments performed. Full article
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Open AccessReview
Requirements of the Smart Factory System: A Survey and Perspective
Machines 2018, 6(2), 23; https://doi.org/10.3390/machines6020023 -
Abstract
With the development of Industry 4.0 and the emergence of the smart factory concept, the traditional philosophy of manufacturing systems will change. The smart factory introduces changes to the factors and elements of traditional manufacturing systems and incorporates the current requirements of smart
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With the development of Industry 4.0 and the emergence of the smart factory concept, the traditional philosophy of manufacturing systems will change. The smart factory introduces changes to the factors and elements of traditional manufacturing systems and incorporates the current requirements of smart systems so that it can compete in the future. An increasing amount of research in both academia and industry is dedicated to transitioning the concept of the smart factory from theory to practice. The purpose of the current research is to highlight the perspectives that shape the smart factory and to suggest approaches and technical support to enable the realization of those perspectives. This paper fills this gap by identifying and analyzing research on smart factories. We suggest a framework to analyze existing research and investigate the elements and features of smart factory systems. Full article
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Open AccessArticle
UML-Based Cyber-Physical Production Systems on Low-Cost Devices under IEC-61499
Machines 2018, 6(2), 22; https://doi.org/10.3390/machines6020022 -
Abstract
Current industry must improve the day-to-day control and industrial communications of its processes in order to bring itself closer to the Industry 4.0 paradigm. To attain these improvements, which aim towards obtaining agile and intelligent manufacturing systems, the IEC-61499 standard is considered to
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Current industry must improve the day-to-day control and industrial communications of its processes in order to bring itself closer to the Industry 4.0 paradigm. To attain these improvements, which aim towards obtaining agile and intelligent manufacturing systems, the IEC-61499 standard is considered to be the main option by many researchers. Despite its benefits, its biggest drawback is the lack of software tools required for an effective design process for distributed control systems. The following work details the implementation of the IEC-61499 standard in low-cost devices using 4DIAC-FORTE for distributed control of a FESTO MPS 200 educational system, by using Unified Modeling Language (UML) diagrams as a software tool for modeling the function blocks (FBs) of the IEC-61499 standard. This work demonstrates a simple and easy way to create distributed systems. Full article
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Open AccessArticle
Non-Destructive Testing for Winding Insulation Diagnosis Using Inter-Turn Transient Voltage Signature Analysis
Machines 2018, 6(2), 21; https://doi.org/10.3390/machines6020021 -
Abstract
The paper proposes a novel approach to assess the integrity of Electrical Insulation Systems (EIS) by evaluating the response of the Transient Voltage Signature Analysis (VSA) to voltage source inverters correlated with changes in the Insulation Capacitance (IC). The involved model structures are
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The paper proposes a novel approach to assess the integrity of Electrical Insulation Systems (EIS) by evaluating the response of the Transient Voltage Signature Analysis (VSA) to voltage source inverters correlated with changes in the Insulation Capacitance (IC). The involved model structures are derived from the in-situ estimation of high-frequency electromagnetic RLMC lumped network parameters. Different physical phenomena such as inductive and capacitive effects, as well as skin and proximity effects are combined. To account for these phenomena, we use an approach based on equivalent multi-transmission line electric circuits with distributed parameters (R: resistances, L, M: self and mutual inductances, and C: capacitances) which are frequency-dependent. Using the finite element method, firstly the turn-to-ground and turn-to-turn capacitance parameters are performed by solving an electrostatic model with a floating electric potential approach, and secondly, the resistance and self/mutual inductances are computed from the strongly coupled magneto-harmonic and total current density equations, including the conduction and displacement eddy current densities. The sensitivity of the capacitances is measured according to insulation thickness, and the dielectric properties are adopted to test the degradation order scenarios of the EIS and comparing their time and frequency domains of transient voltage waveform behavior with respect to healthy assessed insulation systems. Full article
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Open AccessArticle
On the Computational Methods for Solving the Differential-Algebraic Equations of Motion of Multibody Systems
Machines 2018, 6(2), 20; https://doi.org/10.3390/machines6020020 -
Abstract
In this investigation, different computational methods for the analytical development and the computer implementation of the differential-algebraic dynamic equations of rigid multibody systems are examined. The analytical formulations considered in this paper are the Reference Point Coordinate Formulation based on Euler Parameters (RPCF-EP)
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In this investigation, different computational methods for the analytical development and the computer implementation of the differential-algebraic dynamic equations of rigid multibody systems are examined. The analytical formulations considered in this paper are the Reference Point Coordinate Formulation based on Euler Parameters (RPCF-EP) and the Natural Absolute Coordinate Formulation (NACF). Moreover, the solution approaches of interest for this study are the Augmented Formulation (AF) and the Udwadia–Kalaba Equations (UKE). As shown in this paper, the combination of all the methodologies analyzed in this work leads to general, effective, and efficient multibody algorithms that can be readily implemented in a general-purpose computer code for analyzing the time evolution of mechanical systems constrained by kinematic joints. This study demonstrates that multibody algorithm based on the combination of the NACF with the UKE turned out to be the most effective and efficient computational method. The conclusions drawn in this paper are based on the numerical results obtained for a benchmark multibody system analyzed by means of dynamical simulations. Full article
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Open AccessArticle
Use of the Adjoint Method for Controlling the Mechanical Vibrations of Nonlinear Systems
Machines 2018, 6(2), 19; https://doi.org/10.3390/machines6020019 -
Abstract
In this work, the analytical derivation and the computer implementation of the adjoint method are described. The adjoint method can be effectively used for solving the optimal control problem associated with a large class of nonlinear mechanical systems. As discussed in this investigation,
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In this work, the analytical derivation and the computer implementation of the adjoint method are described. The adjoint method can be effectively used for solving the optimal control problem associated with a large class of nonlinear mechanical systems. As discussed in this investigation, the adjoint method represents a broad computational framework, rather than a single numerical algorithm, in which the control problem for nonlinear dynamical systems can be effectively formulated and implemented employing a set of advanced analytical methods as well as an array of well-established numerical procedures. A detailed theoretical derivation and a comprehensive description of the numerical algorithm suitable for the computer implementation of the methodology used for performing the adjoint analysis are provided in the paper. For this purpose, two important cases are analyzed in this work, namely the design of a feedforward control scheme and the development of a feedback control architecture. In this investigation, the control problem relative to the mechanical vibrations of a nonlinear oscillator characterized by a generalized Van der Pol damping model is considered in order to illustrate the effectiveness of the computational algorithm based on the adjoint method by means of numerical experiments. Full article
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Open AccessArticle
Obstacle Avoidance System for Unmanned Ground Vehicles by Using Ultrasonic Sensors
Machines 2018, 6(2), 18; https://doi.org/10.3390/machines6020018 -
Abstract
Artificial intelligence is the ability of a computer to perform the functions and reasoning typical of the human mind. In its purely informatic aspect, it includes the theory and techniques for the development of algorithms that allow machines to show an intelligent ability
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Artificial intelligence is the ability of a computer to perform the functions and reasoning typical of the human mind. In its purely informatic aspect, it includes the theory and techniques for the development of algorithms that allow machines to show an intelligent ability and/or perform an intelligent activity, at least in specific areas. In particular, there are automatic learning algorithms based on the same mechanisms that are thought to be the basis of all the cognitive processes developed by the human brain. Such a powerful tool has already started to produce a new class of self-driving vehicles. With the projections of population growth that will increase until the year 2100 up to 11.2 billion, research on innovating agricultural techniques must be continued. In order to improve the efficiency regarding precision agriculture, the use of autonomous agricultural machines must become an important issue. For this reason, it was decided to test the use of the “Neural Network Toolbox” tool already present in MATLAB to design an artificial neural network with supervised learning suitable for classification and pattern recognition by using data collected by an ultrasonic sensor. The idea is to use such a protocol to retrofit kits for agricultural machines already present on the market. Full article
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Open AccessFeature PaperArticle
Development of a Methodology for Condition-Based Maintenance in a Large-Scale Application Field
Machines 2018, 6(2), 17; https://doi.org/10.3390/machines6020017 -
Abstract
This paper describes a methodology, developed by the authors, for condition monitoring and diagnostics of several critical components in the large-scale applications with machines. For industry, the main target of condition monitoring is to prevent the machine stopping suddenly and thus avoid economic
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This paper describes a methodology, developed by the authors, for condition monitoring and diagnostics of several critical components in the large-scale applications with machines. For industry, the main target of condition monitoring is to prevent the machine stopping suddenly and thus avoid economic losses due to lack of production. Once the target is reached at a local level, usually through an R&D project, the extension to a large-scale market gives rise to new goals, such as low computational costs for analysis, easily interpretable results by local technicians, collection of data from worldwide machine installations, and the development of historical datasets to improve methodology, etc. This paper details an approach to condition monitoring, developed together with a multinational corporation, that covers all the critical points mentioned above. Full article
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Open AccessArticle
Influence of Hub Parameters on Joining Forces and Torque Transmission Output of Plastically-Joined Shaft-Hub-Connections with a Knurled Contact Surface
Machines 2018, 6(2), 16; https://doi.org/10.3390/machines6020016 -
Abstract
A knurled interference fit is a machine part connection made by a plastic joining, which includes the advantages of commonly-used shaft-hub-connections. The combination of the friction and form fit, which are responsible for torque transmission, results in a higher power density than conventional
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A knurled interference fit is a machine part connection made by a plastic joining, which includes the advantages of commonly-used shaft-hub-connections. The combination of the friction and form fit, which are responsible for torque transmission, results in a higher power density than conventional connections. In this paper, parameter gaps are bridged with the aim of enhance the design calculation of the knurled interference fit. Experimental investigations on the shaft chamfer angle (100Cr6) and hub-diameter-ratio (AlSi1MgMn) were performed. The analytical approaches are developed for calculating the joining force and maximal torque capacity by accounting for experimentally investigated loss of load transmission at high hub-diameter-ratios and high shaft chamfer angles. The presented calculation approach is an accurate tool for the assessment of early machine designs of the knurled interference fit and helps to save from having to perform time-extensive tests. Full article
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Open AccessArticle
Theoretical and Experimental Studies of Over-Polishing of Silicon Carbide in Annular Polishing
Machines 2018, 6(2), 15; https://doi.org/10.3390/machines6020015 -
Abstract
Annular polishing technology is an important optical machining method for achieving a high-precision mirror surface on silicon carbide. However, the inevitable over-polishing of the specimen edge in annular polishing deteriorates achieved surface quality. In the present work, we first analytically investigate the kinematic
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Annular polishing technology is an important optical machining method for achieving a high-precision mirror surface on silicon carbide. However, the inevitable over-polishing of the specimen edge in annular polishing deteriorates achieved surface quality. In the present work, we first analytically investigate the kinematic coupling of multiple relative motions in the annular polishing process and subsequently derive an analytical model that addresses the principle of material removal at specimen edge based on the Preston equation and the rigid body contact model. We then perform finite element simulations and experiments involving annular polishing of silicon carbide (SiC), which jointly exhibit agreement with the derived analytical model of material removal. Full article
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Open AccessArticle
Effects of Setting Errors (Insert Run-Outs) on Surface Roughness in Face Milling When Using Circular Inserts
Machines 2018, 6(2), 14; https://doi.org/10.3390/machines6020014 -
Abstract
In face milling, the roughness of the machined surface varies due to the movement of the cutting edge. Changes in roughness parameter values in the axis of rotation (symmetry plane) have been examined at a constant depth of cut for symmetrical milling. In
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In face milling, the roughness of the machined surface varies due to the movement of the cutting edge. Changes in roughness parameter values in the axis of rotation (symmetry plane) have been examined at a constant depth of cut for symmetrical milling. In this paper, the effect of increasing feed per tooth on the topography of the surface is studied in fly-cutting and in multi-point face milling. The study takes into account the axial run-out of the inserts. Theoretical roughness values were modelled, the real values were tested in experiments and in both cases the impact of the run-out of the cutting edges and the change of the chip cross-section were also taken into account. Based on the performed experiments it can be stated that the accuracy of the introduced roughness prediction method increases with the increase in feed and therefore the application of the method in the case of high-feed milling is particularly effective. The results have also shown that the run-out of the insert significantly effects the roughness of the milled surfaces and therefore the measurement and minimization of these setting errors is essential. Full article
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Open AccessArticle
Comparative Analysis of Machining Procedures
Machines 2018, 6(2), 13; https://doi.org/10.3390/machines6020013 -
Abstract
The in-depth analysis of cutting procedure is a topic of particular interest in manufacturing efficiency because in large-scale production the effective use of production capacities and the revenue-increasing capacity of production are key conditions of competitiveness. That is why the analysis of time
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The in-depth analysis of cutting procedure is a topic of particular interest in manufacturing efficiency because in large-scale production the effective use of production capacities and the revenue-increasing capacity of production are key conditions of competitiveness. That is why the analysis of time and material removal rate, which are in close relation to production, are important in planning a machining procedure. In the paper three procedures applied in hard cutting are compared on the basis of these parameters and a new parameter, the practical parameter of material removal rate, is introduced. It measures not only the efficiency of cutting but also that of the whole machining process because it includes the values measured by time analysis as well. In the investigations the material removal rate was analyzed, first on the basis of geometrical data of the component. After that different machining procedures (hard machining) were compared for some typical surfaces. The results can give some useful indications about machining procedure selection. Full article
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Open AccessArticle
System Identification Algorithm for Computing the Modal Parameters of Linear Mechanical Systems
Machines 2018, 6(2), 12; https://doi.org/10.3390/machines6020012 -
Abstract
The goal of this investigation is to construct a computational procedure for identifying the modal parameters of linear mechanical systems. The methodology employed in the paper is based on the Eigensystem Realization Algorithm implemented in conjunction with the Observer/Kalman Filter Identification method (ERA/OKID).
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The goal of this investigation is to construct a computational procedure for identifying the modal parameters of linear mechanical systems. The methodology employed in the paper is based on the Eigensystem Realization Algorithm implemented in conjunction with the Observer/Kalman Filter Identification method (ERA/OKID). This method represents an effective and efficient system identification numerical procedure based on the time domain. The algorithm developed in this work is tested by means of numerical experiments on a full-car vehicle model. To this end, the modal parameters necessary for the design of active and semi-active suspension systems are obtained for the vehicle system considered as an illustrative example. In order to analyze the performance of the methodology developed in this investigation, the system identification numerical procedure was tested considering two case studies, namely a full state measurement and an incomplete state measurement. As expected, the numerical results found for the identified dynamical model showed a good agreement with the modal parameters of the mechanical system model. Furthermore, numerical results demonstrated that the proposed method has good performance considering a scenario in which the signal-to-noise ratio of the input and output measurements is relatively high. The method developed in this paper can be effectively used for solving important engineering problems such as the design of control systems for road vehicles. Full article
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Open AccessArticle
The Setup Design for Selective Laser Sintering of High-Temperature Polymer Materials with the Alignment Control System of Layer Deposition
Machines 2018, 6(1), 11; https://doi.org/10.3390/machines6010011 -
Abstract
This paper presents the design of an additive setup for the selective laser sintering (SLS) of high-temperature polymeric materials, which is distinguished by an original control system for aligning the device for depositing layers of polyether ether ketone (PEEK) powder. The kinematic and
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This paper presents the design of an additive setup for the selective laser sintering (SLS) of high-temperature polymeric materials, which is distinguished by an original control system for aligning the device for depositing layers of polyether ether ketone (PEEK) powder. The kinematic and laser-optical schemes are given. The main cooling circuits are described. The proposed technical and design solutions enable conducting the SLS process in different types of high-temperature polymer powders. The principles of the device adjustment for depositing powder layers based on an integral thermal analysis are disclosed. The PEEK sinterability was shown on the designed installation. The physic-mechanical properties of the tested 3D parts were evaluated in comparison with the known data and showed an acceptable quality. Full article
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Open AccessArticle
Precision CNC Machining of Femoral Component of Knee Implant: A Case Study
Machines 2018, 6(1), 10; https://doi.org/10.3390/machines6010010 -
Abstract
The design and manufacturing of medical implants constitutes an active and highly important field of research, both from a medical and an engineering point of view. From an engineering aspect, the machining of implants is undoubtedly challenging due to the complex shape of
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The design and manufacturing of medical implants constitutes an active and highly important field of research, both from a medical and an engineering point of view. From an engineering aspect, the machining of implants is undoubtedly challenging due to the complex shape of the implants and the associated restrictive geometrical and dimensional requirements. Furthermore, it is crucial to ensure that the surface integrity of the implant is not severely affected, in order for the implant to be durable and wear resistant. In the present work, the methodology of designing and machining the femoral component of total knee replacement using a 3-axis Computer Numerical Control (CNC) machine is presented, and then, the results of the machining process, as well as the evaluation of implant surface quality are discussed in detail. At first, a preliminary design of the components of the knee implant is performed and the planning for the production of the femoral component is implemented in Computed Aided Manufacturing (CAM) software. Then, three femoral components are machined under different process conditions and the surface quality is evaluated in terms of surface roughness. Analysis of the results indicated the appropriate process conditions for each part of the implant surface and led to the determination of optimum machining strategy for the finishing stage. Full article
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Open AccessArticle
The Dimensional Precision of Forming Windows in Bearing Cages
Machines 2018, 6(1), 9; https://doi.org/10.3390/machines6010009 -
Abstract
In the case of double row tapered roller bearings, the windows found in bearing cages could be obtained using various machining methods. Some such machining methods are based on the cold forming process. There are many factors that are able to affect the
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In the case of double row tapered roller bearings, the windows found in bearing cages could be obtained using various machining methods. Some such machining methods are based on the cold forming process. There are many factors that are able to affect the machining accuracy of the windows that exist in bearing cages. On the dimensional precision of windows, the clearance between punches and die, the work stroke length, and the workpiece thickness could exert influence. To evaluate this influence, experimental research was developed taking into consideration the height and the length of the cage window and the distance between the contact elements of the cage. By mathematical processing of the experimental results, empirical mathematical models were determined and analyzed. The empirical models highlighted the intensity of the influence exerted by the considered forming process input factors on the dimensional precision of the windows obtained in bearing cages. Full article
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Open AccessArticle
Modal Coupling in Presence of Dry Friction
Machines 2018, 6(1), 8; https://doi.org/10.3390/machines6010008 -
Abstract
In this paper, we analyze the behavior of a single pad system in the presence of dry friction. The goal is to investigate the path that leads a stable mechanical system to unstable behavior. In doing so, we studied the behavior of a
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In this paper, we analyze the behavior of a single pad system in the presence of dry friction. The goal is to investigate the path that leads a stable mechanical system to unstable behavior. In doing so, we studied the behavior of a discrete three DOF model, a continuous model and a finite element model of the pad. The numerical results are consistent with the experimental investigation conducted on a brake disk for railway application. Full article
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Open AccessArticle
Adaptive Synchronization for Heterogeneous Multi-Agent Systems with Switching Topologies
Machines 2018, 6(1), 7; https://doi.org/10.3390/machines6010007 -
Abstract
This work provides a multi-agent extension of output-feedback model reference adaptive control (MRAC), designed to synchronize a network of heterogeneous uncertain agents. The implementation of this scheme is based on multi-agent matching conditions. The practical advantage of the proposed MRAC is the possibility
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This work provides a multi-agent extension of output-feedback model reference adaptive control (MRAC), designed to synchronize a network of heterogeneous uncertain agents. The implementation of this scheme is based on multi-agent matching conditions. The practical advantage of the proposed MRAC is the possibility of handling the case of the unknown dynamics of the agents only by using the output and the control input of its neighbors. In addition, it is reasonable to consider the case when the communication topology is time-varying. In this work, the time-varying communication leads to a switching control structure that depends on the number of the predecessor of the agents. By using the switching control structure to handle the time-varying topologies, we show that synchronization can be achieved. The multi-agent adaptive switching controller is first analyzed, and numerical simulations based on formation control of simplifier quadcopter dynamics are provided. Full article
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