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Machines, Volume 7, Issue 1 (March 2019)

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Open AccessArticle
Modelling of Temperature Field and Stress–Strain State of the Workpiece with Plasma Coatings during Surface Grinding
Received: 29 December 2018 / Revised: 14 March 2019 / Accepted: 17 March 2019 / Published: 22 March 2019
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Abstract
Plasma coatings play a key role in surface tailoring through providing important advantages for tools during their further application. However, grinding these coatings may cause different defects such as grinding burns and cracks, structural changes to the coating material, and the destruction of [...] Read more.
Plasma coatings play a key role in surface tailoring through providing important advantages for tools during their further application. However, grinding these coatings may cause different defects such as grinding burns and cracks, structural changes to the coating material, and the destruction of adhesive contacts between the coating layer and the substrate. The reason for that is the high heat flux generated in the process of abrasive material removal due to the high friction and stresses. In order to define the optimal conditions for grinding plasma coatings, the mathematical model of the temperature thermal field and the stress–strain state during the grinding process is developed. Based on the temperature, strength, and fracture criteria, this mathematical model makes it possible to define the functional relationship between the technological characteristics of the grinding process and the conditions that provide the required quality of surface processing. The role of the structural defects that are generated while coatings are being sprayed, as well as during coating adhesion, is also considered. An algorithm developed to present the results of the modelling process enables checking if the input parameters meet the condition of zero-defect grinding of a workpiece, and determining an expected surface roughness. Input parameters include the grinding wheel geometry, its abrasive properties, the wheel speed, longitudinal and transverse motion, grinding depth, and the use of the cutting fluid. Experimental testing of this study shows the way in which the regime of the grinding process and different grinding wheel parameters influence the physical and mechanical properties of the surface layer. Full article
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Open AccessArticle
Power Flows in Compound Transmissions for Hybrid Vehicles
Received: 29 January 2019 / Revised: 3 March 2019 / Accepted: 5 March 2019 / Published: 15 March 2019
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Abstract
Hybrid electric vehicle (HEV) traction systems are the most promising technologies being characterized by high performance, high fuel efficiency, low emissions and long operating range. Significant improvements can be achieved equipping transmissions with variable transmission ratio such as power-split transmission and a compound [...] Read more.
Hybrid electric vehicle (HEV) traction systems are the most promising technologies being characterized by high performance, high fuel efficiency, low emissions and long operating range. Significant improvements can be achieved equipping transmissions with variable transmission ratio such as power-split transmission and a compound power-split electric continuously variable transmission (eCVT). These systems have been introduced to improve vehicle global efficiency since they can maximize the efficiency in different operating conditions. Optimal design and control of these systems leads improvements in vehicles performance and mathematical models, which support the preliminary design phase, can play a key role in this field. In this work, the internal power circulations of “four-port-mechanical-power split device are determined through a dynamic analysis.” Finally, the efficiency of the compound transmission is analytically evaluated, assuming that the overall losses are linked to the eCVT variator. Full article
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Open AccessArticle
A Product Conceptual Design Method Based on Evolutionary Game
Received: 3 December 2018 / Revised: 19 February 2019 / Accepted: 4 March 2019 / Published: 5 March 2019
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Abstract
In this paper, an intelligent-design method to deal with conceptual optimization is proposed for the decisive impact of the concept on the product-development cycle cost and performance. On the basis of matter-element analysis, an effective functional-structure combination model satisfying multiple constraints is first [...] Read more.
In this paper, an intelligent-design method to deal with conceptual optimization is proposed for the decisive impact of the concept on the product-development cycle cost and performance. On the basis of matter-element analysis, an effective functional-structure combination model satisfying multiple constraints is first established, which maps the product characteristics obtained by expert research and customer-requirements analysis of the function and structure domain. Then, the Evolutionary Game Algorithm (EGA) was utilized to solve the model, in which a strategy-combination space is mapped to the solution-search space of the conceptual-solution problem, and the game-utility function is mapped to the objective functions of concept evaluation. Constant disturbance and Best-Response Correspondence were applied cross-repeatedly until the optimal equilibrium Pareto state corresponding to the global optimal solution was obtained. Finally, the method was simulated on MATLAB 8.3 and applied to the design for fixed winch hoist, which greatly shortens its design cycle. Full article
(This article belongs to the Special Issue Smart Manufacturing)
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Open AccessArticle
Optimization of Gerotor Pumps with Asymmetric Profiles through an Evolutionary Strategy Algorithm
Received: 29 January 2019 / Revised: 20 February 2019 / Accepted: 22 February 2019 / Published: 1 March 2019
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Abstract
Gerotor pumps are widely used for fuel and lubricating oil distribution, since they provide an economic and compact solution for low-pressure fluid systems. Made of two internally coupled gears, their behavioral and operative performances are strictly tied to their geometrical designs. Traditionally, the [...] Read more.
Gerotor pumps are widely used for fuel and lubricating oil distribution, since they provide an economic and compact solution for low-pressure fluid systems. Made of two internally coupled gears, their behavioral and operative performances are strictly tied to their geometrical designs. Traditionally, the external gear features circular lobes that give origin to a cycloidal profile for the internal rotor. In this paper, the use of profiles based on asymmetric lobes made of elliptic arcs is further explored and expanded. At first, a complete mathematical framework describing the pump geometry and its dynamic behavior is provided, while algorithms used to compute a selected number of performance indexes are presented and when possible, verified. Hence, a single-objective optimization procedure is applied to the traditional cycloidal profile, in order to minimize each of the following quantities: the flow rate irregularity, the expected wear rate, and the estimated rotor mass. Finally, a multi-objective optimization process based on evolutionary strategy is employed, to obtain several asymmetric profiles minimizing the combination of two or more performance indexes. The results are hence compared, and the merits associated with the use of asymmetric lobes are presented. Full article
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Open AccessArticle
Optimization of Friction Behavior Characteristics by Coating with Solid Lubricants
Received: 30 December 2018 / Revised: 4 February 2019 / Accepted: 7 February 2019 / Published: 9 February 2019
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Abstract
Increasing the lifetime of machine elements whose operation involves the development of friction processes and diminishing energy losses by friction can be achieved by using solid lubricants. In this regard, a method applied to improve the friction behavior of machine elements is electrostatic [...] Read more.
Increasing the lifetime of machine elements whose operation involves the development of friction processes and diminishing energy losses by friction can be achieved by using solid lubricants. In this regard, a method applied to improve the friction behavior of machine elements is electrostatic coating of the surfaces of interest with polyester layers that include particles of solid lubricants, such as molybdenum disulfide or graphite. Experimental research was conducted to highlight the influence of normal force, the concentration of solid lubricant particles in polyester, and specific sliding between surfaces involved in the friction process on the deposited layer’s lifetime and on the friction coefficient. Grey analysis was employed to identify sets of input factors that would lead to the most convenient values of the lifetime and energy friction losses when using polyester layers that incorporate molybdenum or graphite particles. Specialized software was elaborated in a MATLAB environment to use the grey relational analysis in identifying the optimal values of the process input factors for distinct weights of the output parameters. Full article
(This article belongs to the Special Issue Advances in CAD/CAM/CAE Technologies)
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Open AccessArticle
The Yawing Behavior of Horizontal-Axis Wind Turbines: A Numerical and Experimental Analysis
Received: 21 December 2018 / Revised: 1 February 2019 / Accepted: 4 February 2019 / Published: 8 February 2019
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Abstract
The yawing of horizontal-axis wind turbines (HAWT) is a major topic in the comprehension of the dynamical behavior of these kinds of devices. It is important for the study of mechanical loads to which wind turbines are subjected and it is important for [...] Read more.
The yawing of horizontal-axis wind turbines (HAWT) is a major topic in the comprehension of the dynamical behavior of these kinds of devices. It is important for the study of mechanical loads to which wind turbines are subjected and it is important for the optimization of wind farms because the yaw active control can steer the wakes between nearby wind turbines. On these grounds, this work is devoted to the numerical and experimental analysis of the yawing behavior of a HAWT. The experimental tests have been performed at the wind tunnel of the University of Perugia on a three-bladed small HAWT prototype, having two meters of rotor diameter. Two numerical set ups have been selected: a proprietary code based on the Blade Element Momentum theory (BEM) and the aeroelastic simulation software FAST, developed at the National Renewable Energy Laboratory (NREL) in Golden, CO, USA. The behavior of the test wind turbine up to ± 45 of yaw offset is studied. The performances (power coefficient C P ) and the mechanical behavior (thrust coefficient C T ) are studied and the predictions of the numerical models are compared against the wind tunnel measurements. The results for C T inspire a subsequent study: its behavior as a function of the azimuth angle is studied and the periodic component equal to the blade passing frequency 3P is observed. The fluctuation intensity decreases with the yaw angle because the distance between tower and blade increases. Consequently, the tower interference is studied through the comparison of measurements and simulations as regards the fore-aft vibration spectrum and the force on top of the tower. Full article
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Open AccessArticle
Dynamic Performance of a Squeeze Film Damper with a Cylindrical Roller Bearing under a Large Static Radial Loading Range
Received: 20 December 2018 / Revised: 29 January 2019 / Accepted: 29 January 2019 / Published: 3 February 2019
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Abstract
Turbomachine rotors, supported by little damped rolling element bearings, are generally sensitive to unbalance excitation. Accordingly, most machines incorporate squeeze film damper technology to dissipate mechanical energy caused by rotor vibrations and to ensure stable operation. When developing a novel geared turbomachine able [...] Read more.
Turbomachine rotors, supported by little damped rolling element bearings, are generally sensitive to unbalance excitation. Accordingly, most machines incorporate squeeze film damper technology to dissipate mechanical energy caused by rotor vibrations and to ensure stable operation. When developing a novel geared turbomachine able to cover a large power range, a uniform mechanical drivetrain needs to perform well over the large operational loading range. Especially, the rotor support, containing a squeeze film damper and cylindrical roller bearing in series, is of vital importance in this respect. Thus, the direct objective of this research project was to map the performance of the envisioned rotor support by estimating the damping ratio based on the simulated and measured vibration response during run-up. An academic test rig was developed to provide an in-depth analysis on the key components in a more controlled setting. Both the numerical simulation and measurement results exposed severe vibration problems for an insufficiently radial loaded bearing due to a pronounced anisotropic bearing stiffness. As a result, a split first whirl mode arose with its backward component heavily triggered by the synchronous unbalance excitation. Hence, the proposed SFD does not function properly in the lower radial loading range. Increasing the static load on the bearing or providing a modified rotor support for the lower power variants will help mitigating the vibration issues. Full article
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Open AccessArticle
A Comparative Study between Regression and Neural Networks for Modeling Al6082-T6 Alloy Drilling
Received: 31 December 2018 / Revised: 28 January 2019 / Accepted: 29 January 2019 / Published: 2 February 2019
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Abstract
Apart from experimental research, the development of accurate and efficient models is considerably important in the field of manufacturing processes. Initially, regression models were significantly popular for this purpose, but later, the soft computing models were proven as a viable alternative to the [...] Read more.
Apart from experimental research, the development of accurate and efficient models is considerably important in the field of manufacturing processes. Initially, regression models were significantly popular for this purpose, but later, the soft computing models were proven as a viable alternative to the established models. However, the effectiveness of soft computing models can be often dependent on the size of the experimental dataset, and it can be lower compared to that of the regression models for a small-sized dataset. In the present study, it is intended to conduct a comparison of the performance of various neural network models, such as the Multi-layer Perceptron (MLP), the Radial Basis Function Neural Network (RBF-NN), and the Adaptive Neuro-Fuzzy Inference System (ANFIS) models with the performance of a multiple regression model. For the development of the models, data from drilling experiments on an Al6082-T6 workpiece for various process conditions are employed, and the performance of models related to thrust force (Fz) and cutting torque (Mz) is assessed based on several criteria. From the analysis, it was found that the MLP models were superior to the other neural networks model and the regression model, as they were able to achieve a relatively lower prediction error for both models of Fz and Mz. Full article
(This article belongs to the Special Issue Advances in CAD/CAM/CAE Technologies)
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Open AccessArticle
Development of a Low-Cost Vibration Measurement System for Industrial Applications
Received: 2 October 2018 / Revised: 2 January 2019 / Accepted: 8 January 2019 / Published: 1 February 2019
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Abstract
Vibration-Based Condition Monitoring (VBCM) provides essential data to perform Condition-Based Maintenance for efficient, optimal, reliable, and safe industrial machinery operation. However, equipment required to perform VBCM is often relatively expensive. In this paper, a low-cost vibration measurement system based on a microcontroller platform [...] Read more.
Vibration-Based Condition Monitoring (VBCM) provides essential data to perform Condition-Based Maintenance for efficient, optimal, reliable, and safe industrial machinery operation. However, equipment required to perform VBCM is often relatively expensive. In this paper, a low-cost vibration measurement system based on a microcontroller platform is presented. The FRDM K64F development board was selected as the most suitable for fulfilling the system requirements. The industrial environment is highly contaminated by noise (electromagnetic, combustion, airborne, sound borne, and mechanical noise). Developing a proper antialiasing filter to reduce industrial noise is a real challenge. In order to validate the developed system, evaluations of frequency response and phase noise were carried out. Additionally, vibration measurements were recorded in the industry under different running conditions and machine configurations. Data were collected simultaneously using a standard reference system and the low-cost vibration measurement system. Results were processed using Fast Fourier Transform and Welch’s method. Finally, a low-cost vibration measurement system was successfully created. The validation process demonstrates the robustness, reliability, and accuracy of this research approach. Results confirm a correlation between signal frequency spectrum obtained using both measurement systems. We also introduce new guidelines for practical data storage, communications, and validation process for vibration measurements. Full article
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Open AccessArticle
Influence of Ball-Burnishing Process on Surface Topography Parameters and Tribological Properties of Hardened Steel
Received: 20 December 2018 / Revised: 14 January 2019 / Accepted: 15 January 2019 / Published: 19 January 2019
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Abstract
The ball-burnishing process is a particular finishing treatment that can improve selected properties of different materials. In the present study, the ball-burnishing technique was used to investigate the effect of input parameters of processes on selected surface layer features like surface roughness and [...] Read more.
The ball-burnishing process is a particular finishing treatment that can improve selected properties of different materials. In the present study, the ball-burnishing technique was used to investigate the effect of input parameters of processes on selected surface layer features like surface roughness and residual stresses of the 42CrMo4 steel surfaces. The burnishing process was conducted on Haas CNC Vertical Mill Center VF-3 using a tool with tungsten carbide tip. A further objective of our research was to improve tribological properties of the aforementioned steel by the ball-burnishing process. The results of the investigations showed that it was possible to reduce the root mean square height of the surface Sq from 0.522 μm to 0.051 μm and to increase wear resistance compared to ground samples. Full article
(This article belongs to the Special Issue Advances in CAD/CAM/CAE Technologies)
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Open AccessArticle
Tuning and Feasibility Analysis of Classical First-Order MIMO Non-Linear Sliding Mode Control Design for Industrial Applications
Received: 30 November 2018 / Revised: 11 January 2019 / Accepted: 14 January 2019 / Published: 18 January 2019
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Abstract
Model-based control techniques have been gaining more and more interest these days. These complex control systems are mostly based on theories, such as feedback linearization, model predictive control, adaptive and robust control. In this paper the latter approach is investigated, in particular, sliding [...] Read more.
Model-based control techniques have been gaining more and more interest these days. These complex control systems are mostly based on theories, such as feedback linearization, model predictive control, adaptive and robust control. In this paper the latter approach is investigated, in particular, sliding mode (SM) control is analyzed. While several works on the description and application of SM control on single-input single-output systems can easily be found, its application on multi-input multi-output systems is not examined in depth at the same level. Hence, this work aims at formalizing some theoretical complements about the necessary conditions for the feasibility of the SM control for multi-input-multi-output systems. Furthermore, in order to obtain the desired performance from the control system, a method for parameter tuning is proposed in the particular case in which the relative degree of the controlled channels is equal to one. Finally, a simple control problem example is shown with the aim of stressing the benefits derived from the application of the theoretical complements described here. Full article
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Open AccessArticle
Optimizing Weight of Housing Elements of Two-stage Reducer by Using the Topology Management Optimization Capabilities Integrated in SOLIDWORKS: A Case Study
Received: 15 December 2018 / Revised: 8 January 2019 / Accepted: 11 January 2019 / Published: 15 January 2019
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Abstract
This paper presents the results of a conducted topology management optimization study based on the finite element analysis on a two-stage spur gear reducer housing body and cover using the SOLIDWORKS Simulation module. The main goal of the study is to optimize the [...] Read more.
This paper presents the results of a conducted topology management optimization study based on the finite element analysis on a two-stage spur gear reducer housing body and cover using the SOLIDWORKS Simulation module. The main goal of the study is to optimize the overall weight of the reducer by thinning specific areas of the casted gearbox housing elements according to the calculated minimal strain energy. The topology optimization algorithm that is used in current research gives an optimal structural shape of the housing elements of the reducer with the largest stiffness, considering the given amount of mass that will be removed from the initial design space. The complete sequence of steps for conducting the topology management optimization study is shown, taking into account the constraints arising from the construction features and the method of manufacturing the housing elements of the gear reducer. Conclusions on the use of the topology optimization results are given and potential directions for further development of the approach are also identified. Full article
(This article belongs to the Special Issue Advances in CAD/CAM/CAE Technologies)
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Open AccessArticle
A Study of the Impact of Pitch Misalignment on Wind Turbine Performance
Received: 26 November 2018 / Revised: 22 December 2018 / Accepted: 10 January 2019 / Published: 15 January 2019
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Abstract
Pitch angle control is the most common means of adjusting the torque of wind turbines. The verification of its correct function and the optimization of its control are therefore very important for improving the efficiency of wind kinetic energy conversion. On these grounds, [...] Read more.
Pitch angle control is the most common means of adjusting the torque of wind turbines. The verification of its correct function and the optimization of its control are therefore very important for improving the efficiency of wind kinetic energy conversion. On these grounds, this work is devoted to studying the impact of pitch misalignment on wind turbine power production. A test case wind farm sited onshore, featuring five multi-megawatt wind turbines, was studied. On one wind turbine on the farm, a maximum pitch imbalance between the blades of 4.5 ° was detected; therefore, there was an intervention for recalibration. Operational data were available for assessing production improvement after the intervention. Due to the non-stationary conditions to which wind turbines are subjected, this is generally a non-trivial problem. In this work, a general method was formulated for studying this kind of problem: it is based on the study, before and after the upgrade, of the residuals between the measured power output and a reliable model of the power output itself. A careful formulation of the model is therefore crucial: in this work, an automatic feature selection algorithm based on stepwise multivariate regression was adopted, and it allows identification of the most meaningful input variables for a multivariate linear model whose target is the power of the wind turbine whose pitch has been recalibrated. This method can be useful, in general, for the study of wind turbine power upgrades, which have been recently spreading in the wind energy industry, and for the monitoring of wind turbine performances. For the test case of interest, the power of the recalibrated wind turbine is modeled as a linear function of the active and reactive power of the nearby wind turbines, and it is estimated that, after the intervention, the pitch recalibration provided a 5.5% improvement in the power production below rated power. Wind turbine practitioners, in general, should pay considerable attention to the pitch imbalance, because it increases loads and affects the residue lifetime; in particular, the results of this study indicate that severe pitch misalignment can heavily impact power production. Full article
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Open AccessEditorial
Acknowledgement to Reviewers of Machines in 2018
Published: 11 January 2019
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Abstract
Rigorous peer-review is the corner-stone of high-quality academic publishing [...] Full article
Open AccessArticle
Design to Achieve Accuracy in Ink-Jet Cylindrical Printing Machines
Received: 3 December 2018 / Revised: 4 January 2019 / Accepted: 8 January 2019 / Published: 11 January 2019
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Abstract
Machines for direct digital inkjet printing on cylindrical containers are a new technology out on the market. The commercialization in the industrial sector has been affected by their high precision. This led to the use of mechanisms with narrow manufacturing tolerances and to [...] Read more.
Machines for direct digital inkjet printing on cylindrical containers are a new technology out on the market. The commercialization in the industrial sector has been affected by their high precision. This led to the use of mechanisms with narrow manufacturing tolerances and to the searches for topologies that have the least accumulated error without affecting quality. Machines with topologies that work on flat substrates have printing and productivity problems working on cylindrical substrates. This research paper presents the qualitative design of direct digital inkjet printers working over cylindrical substrates comparing five mechanical topologies; three topologies with radial distribution and two topologies with parallel distribution. The aim of these topologies is to find the precision, quality and efficiency of the printer taking into account the restrictions present in its construction. Each topology has separate constitutive mechanisms, the tolerance ranges between the movements of the print head and the substrate in order to determine precision are analyzed. Out of the five topologies described and analyzed in the phase diagram in section 3, three of them meet the requirements. One of the three topologies that meet the requirements is not being developed due to current technological limitations. Full article
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Open AccessArticle
Forward and Inverse Dynamics of a Unicycle-Like Mobile Robot
Received: 6 November 2018 / Revised: 3 January 2019 / Accepted: 8 January 2019 / Published: 11 January 2019
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Abstract
In this research work, a new method for solving forward and inverse dynamic problems of mechanical systems having an underactuated structure and subjected to holonomic and/or nonholonomic constraints is developed. The method devised in this paper is based on the combination of the [...] Read more.
In this research work, a new method for solving forward and inverse dynamic problems of mechanical systems having an underactuated structure and subjected to holonomic and/or nonholonomic constraints is developed. The method devised in this paper is based on the combination of the Udwadia-Kalaba Equations with the Underactuation Equivalence Principle. First, an analytical method based on the Udwadia-Kalaba Equations is employed in the paper for handling dynamic and control problems of nonlinear nonholonomic mechanical systems in the same computational framework. Subsequently, the Underactuation Equivalence Principle is used for extending the capabilities of the Udwadia-Kalaba Equations from fully actuated mechanical systems to underactuated mechanical systems. The Underactuation Equivalence Principle represents an efficient method recently developed in the field of classical mechanics. The Underactuation Equivalence Principle is used in this paper for mathematically formalizing the underactuation property of a mechanical system considering a particular set of nonholonomic algebraic constraints defined at the acceleration level. On the other hand, in this study, the Udwadia-Kalaba Equations are analytically reformulated in a mathematical form suitable for treating inverse dynamic problems. By doing so, the Udwadia-Kalaba Equations are employed in conjunction with the Underactuation Equivalence Principle for developing a nonlinear control method based on an inverse dynamic approach. As shown in detail in this investigation, the proposed method can be used for analytically solving in an explicit manner the forward and inverse dynamic problems of several nonholonomic mechanical systems. In particular, the tracking control of the unicycle-like mobile robot is considered in this investigation as a benchmark example. Numerical experiments on the dynamic model of the unicycle-like mobile robot confirm the effectiveness of the nonlinear dynamic and control approaches developed in this work. Full article
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Open AccessArticle
Comprehensive Parameters Identification and Dynamic Model Validation of Interior-Mount Line-Start Permanent Magnet Synchronous Motors
Received: 26 November 2018 / Revised: 30 December 2018 / Accepted: 2 January 2019 / Published: 7 January 2019
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Abstract
The application of line-start permanent magnet synchronous motors (LSPMSMs) is rapidly spreading due to their advantages of high efficiency, high operational power factor, being self-starting, rendering them as highly needed in many applications in recent years. Although there have been standard methods for [...] Read more.
The application of line-start permanent magnet synchronous motors (LSPMSMs) is rapidly spreading due to their advantages of high efficiency, high operational power factor, being self-starting, rendering them as highly needed in many applications in recent years. Although there have been standard methods for the identification of parameters of synchronous and induction machines, most of them do not apply to LSPMSMs. This paper presents a study and analysis of different parameter identification methods for interior mount LSPMSM. Experimental tests have been performed in the laboratory on a 1-hp interior mount LSPMSM. The measurements have been validated by investigating the performance of the machine under different operating conditions using a developed qd0 mathematical model and an experimental setup. The dynamic and steady-state performance analyses have been performed using the determined parameters. It is found that the experimental results are close to the mathematical model results, confirming the accuracy of the studied test methods. Therefore, the output of this study will help in selecting the proper test method for LSPMSM. Full article
(This article belongs to the Special Issue Advances in Electrical Machines and Drives)
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Open AccessArticle
Robust Control of Small Turbojet Engines
Received: 2 October 2018 / Revised: 14 December 2018 / Accepted: 17 December 2018 / Published: 4 January 2019
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Abstract
Modern turbojet engines mainly use computerized digital engine control systems. This opens the way for application of advanced algorithms aimed at increasing their operational efficiency and safety. The theory of robust control is a set of methods known for good results in complex [...] Read more.
Modern turbojet engines mainly use computerized digital engine control systems. This opens the way for application of advanced algorithms aimed at increasing their operational efficiency and safety. The theory of robust control is a set of methods known for good results in complex control tasks, making them ideal candidates for application in the current turbojet engine control units. Different methodologies in the design of robust controllers, utilizing a small turbojet engine with variable exhaust nozzle designated as iSTC-21v, were therefore investigated in the article. The resulting controllers were evaluated for efficiency in laboratory conditions. The aim was to find a suitable approach and design method for robust controllers, taking into account the limitations and specifics of a real turbojet engine and its hardware, contrary to most studies which have used only simulated environments. The article shows the most effective approach in the design of robust controllers and the resulting speed controllers for a class of small turbojet engines, which can be applied in a discrete digital control environment. Full article
(This article belongs to the Special Issue Advanced Control Systems and Optimization Techniques)
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Open AccessArticle
Application of IoT-Aided Simulation to Manufacturing Systems in Cyber-Physical System
Received: 26 October 2018 / Revised: 15 December 2018 / Accepted: 17 December 2018 / Published: 3 January 2019
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Abstract
With the rapid development of mobile and wireless networking technologies, data has become more ubiquitous and the IoT (Internet of Things) is attracting much attention due to high expectations for enabling innovative service, efficiency, and productivity improvement. In next-generation manufacturing, the digital twin [...] Read more.
With the rapid development of mobile and wireless networking technologies, data has become more ubiquitous and the IoT (Internet of Things) is attracting much attention due to high expectations for enabling innovative service, efficiency, and productivity improvement. In next-generation manufacturing, the digital twin (DT) has been proposed as a new concept and simulation tool for collecting and synchronizing real-world information in real time in cyber space to cope with the challenges of smart factories. Although the DT is considered a challenging technology, it is still at the conceptual stage and only a few studies have specifically discussed methods for its construction and implementation. In this study, we first explain the concept of DT and important issues involved in developing it within an IoT-aided manufacturing environment. Then, we propose a DT construction framework and scheme for inputting data derived from the IoT into a simulation model. Finally, we describe how we verify the effectiveness of the proposed framework and scheme, by constructing a DT-oriented simulation model for an IoT-aided manufacturing system. Full article
(This article belongs to the Special Issue Smart Manufacturing)
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Open AccessArticle
Numerical Fatigue Analysis of Induction-Hardened and Mechanically Post-Treated Steel Components
Received: 2 November 2018 / Revised: 12 December 2018 / Accepted: 21 December 2018 / Published: 2 January 2019
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Abstract
This paper presents a numerical simulation chain covering induction hardening (IH), superimposed stroke peening (StrP) as mechanical post-treatment, and a final fatigue assessment considering local material properties. Focusing on a notched round specimen as representative for engineering components, firstly, the electro-magnetic-thermal simulation of [...] Read more.
This paper presents a numerical simulation chain covering induction hardening (IH), superimposed stroke peening (StrP) as mechanical post-treatment, and a final fatigue assessment considering local material properties. Focusing on a notched round specimen as representative for engineering components, firstly, the electro-magnetic-thermal simulation of the inductive heating is performed with the software Comsol®. Secondly, the thermo-metallurgical-mechanical analysis of the hardening process is conducted by means of a user-defined interface, utilizing the software Sysweld®. Thirdly, mechanical post-treatment is numerically simulated by Abaqus®. Finally, a strain-based approach considering the evaluated local material properties is applied, which reveals sound accordance to the fatigue tests results, exhibiting a minor conservative deviation of only up to two per cent, which validates the applicability of the presented numerical fatigue approach. Full article
(This article belongs to the Special Issue Advances in CAD/CAM/CAE Technologies)
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