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Machines, Volume 5, Issue 4 (December 2017)

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Research

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Open AccessArticle Quantification of a Low-Cost Stretchable Conductive Sensor Using an Expansion/Contraction Simulator Machine: A Step towards Validation of a Noninvasive Cardiac and Respiration Monitoring Prototype
Machines 2017, 5(4), 22; doi:10.3390/machines5040022
Received: 18 May 2017 / Revised: 29 September 2017 / Accepted: 1 October 2017 / Published: 6 October 2017
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Abstract
The use of wearable sensors in health monitoring is increasing dramatically, largely due to their convenience and low-cost. Understanding the accuracy of any given sensor is paramount to avoid potential misdiagnosis. Commercially available electro-resistive band (ERB) sensors have been integrated into several newly
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The use of wearable sensors in health monitoring is increasing dramatically, largely due to their convenience and low-cost. Understanding the accuracy of any given sensor is paramount to avoid potential misdiagnosis. Commercially available electro-resistive band (ERB) sensors have been integrated into several newly developed wearable devices with a view to using these sensors to monitor a range of respiratory and cardiovascular metrics. Quantification of the ERBs is a necessary to step towards validation of these prototypes, as it provides valuable information, which could be exploited for compensation and ultimately, for improvement of their performance. Here, we present an analysis of the ERB sensors using an expansion/contraction simulator machine. Using the developed rig, the characteristics of four ERBs were compared with a linear displacement sensor (string potentiometer) during continuous use over the course of four-and-a-half days to investigate the error and nonlinearity of the ERBs. The analysis of the recorded data includes calculation and comparison of the total harmonic distortions of the two sensors to quantify ERB nonlinearity. Moreover, comparisons between the peak-to-peak voltages and signal-to-noise ratios of the ERB and string potentiometer demonstrate the effect nonlinearity on these factors. This paper demonstrates the nonlinearity of ERBs and highlights the implications for their use in practice. Full article
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Open AccessArticle Toilet Assistive System Designed for the Reduction of Accidental Falls in the Bathroom Using Admittance Controller
Machines 2017, 5(4), 23; doi:10.3390/machines5040023
Received: 7 August 2017 / Revised: 2 October 2017 / Accepted: 4 October 2017 / Published: 13 October 2017
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Abstract
This paper suggests an assistive system for the toilet with the objective of measuring human activities and to provide intelligent mechanical assistance to help seating and standing. The project intends to develop a seating assistance as a technical aid in order to reduce
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This paper suggests an assistive system for the toilet with the objective of measuring human activities and to provide intelligent mechanical assistance to help seating and standing. The project intends to develop a seating assistance as a technical aid in order to reduce accidents and falls in the bathroom. The preferred technique is human-robot physical interaction algorithms known in collaborative robotics (cobot) and adapting it to a personalized assistance technology installed on a smart toilet. First, the design of the mechanical assistance is presented. Then, an admittance controller is designed and implemented in order to help the user in a similar way as a cobot could be used. This technique could be used to assist the user and improve balance with adequate training and an adequate configuration of the admittance controller. Full article
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Open AccessFeature PaperArticle Virtual Reference Feedback Tuning of Model-Free Control Algorithms for Servo Systems
Machines 2017, 5(4), 25; doi:10.3390/machines5040025
Received: 30 September 2017 / Revised: 20 October 2017 / Accepted: 22 October 2017 / Published: 24 October 2017
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Abstract
This paper proposes the combination of two data-driven techniques, namely virtual reference feedback tuning (VRFT) and model-Free Control (MFC) in terms of the VRFT of MFC algorithms dedicated to servo systems. VRFT ensures the automatic optimal computation of the parameters of three MFC
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This paper proposes the combination of two data-driven techniques, namely virtual reference feedback tuning (VRFT) and model-Free Control (MFC) in terms of the VRFT of MFC algorithms dedicated to servo systems. VRFT ensures the automatic optimal computation of the parameters of three MFC algorithms represented by intelligent proportional (iP), intelligent proportional-integral (iPI), and intelligent proportional-integral-derivative (iPID) controllers. The combination of MFC and VRFT leads to a novel mixed MFC-VRFT approach. The approach is validated by experimental results related to the angular speed control of modular servo system laboratory equipment. The performance of the control systems with the MFC algorithms (iP, iPI, and iPID controllers) tuned by the mixed MFC-VRFT approach is compared with that of control systems with MFC algorithms tuned by a metaheuristics gravitational search algorithm (GSA) optimizer, and of control systems with I, PI and PID controllers optimally tuned by VRFT and GSA in the same optimization problem. Full article
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Open AccessArticle Modeling, Analysis, and Realization of Permanent Magnet Synchronous Motor Current Vector Control by MATLAB/Simulink and FPGA
Machines 2017, 5(4), 26; doi:10.3390/machines5040026
Received: 13 September 2017 / Revised: 8 October 2017 / Accepted: 8 October 2017 / Published: 28 October 2017
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Abstract
In this paper, we present the modeling, analysis, and realization of current vector control for a permanent magnet synchronous motor (PMSM) drive using MATLAB/Simulink and a field programmable gate array (FPGA). In AC motor drive systems, most of the current vector controls are
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In this paper, we present the modeling, analysis, and realization of current vector control for a permanent magnet synchronous motor (PMSM) drive using MATLAB/Simulink and a field programmable gate array (FPGA). In AC motor drive systems, most of the current vector controls are realized by digital signal processors (DSPs) because of their complete and compact hardware functions. However, the performances of drive systems realized by low-cost DSP are limited by the hardware structure and computation capacity, which may lead to the difficulty of reaching a fast enough response, above all, for those motors with a small electrical time constant. Therefore, we use FPGA to speed up the calculation about the current vector control to attain a fast response. Simulations and practical experimental results are used to verify the correctness and performance of the designed full hardware system. Full article
(This article belongs to the Special Issue High Speed Motors and Drives: Design, Challenges and Applications)
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Open AccessArticle The Decision making System for Condition Monitoring of Induction Motors Based on Vector Control Model
Machines 2017, 5(4), 27; doi:10.3390/machines5040027
Received: 23 October 2017 / Revised: 7 November 2017 / Accepted: 9 November 2017 / Published: 12 November 2017
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Abstract
Induction motors are mainly used for variable load applications and it is vital to have a condition monitoring system with capabilities to diagnose motor faults in variable load conditions. The environment noise varies has non-linear relation with motor load and it challenges the
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Induction motors are mainly used for variable load applications and it is vital to have a condition monitoring system with capabilities to diagnose motor faults in variable load conditions. The environment noise varies has non-linear relation with motor load and it challenges the decision making capability of the condition monitoring system. This paper addresses the issue of reliable decision making on the existence of bearing faults in variable load conditions. Two type of threshold schemes have been proposed to reliably diagnose bearing faults in Park vector modulus spectrum. The performance of the developed threshold based condition monitoring system has been analyzed theoretically and experimentally. Full article
(This article belongs to the Special Issue Machinery Condition Monitoring and Industrial Analytics)
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Open AccessArticle Utilizing Sequential Action Control Method in GaN-Based High-Speed Drive for BLDC Motor
Machines 2017, 5(4), 28; doi:10.3390/machines5040028
Received: 6 October 2017 / Revised: 27 October 2017 / Accepted: 16 November 2017 / Published: 21 November 2017
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Abstract
This paper presents a hybrid model–based control algorithm that combines Model Predictive Control (MPC) and Sequential Action Control (SAC) deployed in a high-speed drive for Brushless DC (BLDC) motor by using a DC-DC converter with Gallium Nitride (GaN) switches. GaN FETs are selected
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This paper presents a hybrid model–based control algorithm that combines Model Predictive Control (MPC) and Sequential Action Control (SAC) deployed in a high-speed drive for Brushless DC (BLDC) motor by using a DC-DC converter with Gallium Nitride (GaN) switches. GaN FETs are selected because of their higher speed and lower power loss as compared with traditional Si switches. In the proposed framework, SAC processes the initial values of the control variables as well as their time of application and their duration in MPC loop. After receiving the underlying estimation of future contribution from SAC, MPC consolidates it with current input and predicts future control values by using the system state space model. This hybrid control conserves control effort and reduces sensitivity to initial conditions. In this way, converter’s output voltage is controlled to produce the reference speed at the motor output. National Instrument PXIe-6356 module is utilized as the interface between software and hardware that is a multi-function, LabVIEW-compatible data acquisition device. The viability of the proposed hybrid optimization for the high-speed drive is confirmed numerically by utilizing MATLAB/Simulink and approved experimentally using a Gallium Nitride (GaN) half-bridge DC-DC converter. Full article
(This article belongs to the Special Issue High Speed Motors and Drives: Design, Challenges and Applications)
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Open AccessArticle Mechatronic Design for an Extrusion-Based Additive Manufacturing Machine
Machines 2017, 5(4), 29; doi:10.3390/machines5040029
Received: 15 October 2017 / Revised: 12 November 2017 / Accepted: 24 November 2017 / Published: 29 November 2017
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Abstract
3D printers, especially in the implementation of innovative extrusion processes which do not have a long history of development, are often built by adapting mechanical designs, drives and controls previously developed for generic machine tools. This is done through a process of choice
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3D printers, especially in the implementation of innovative extrusion processes which do not have a long history of development, are often built by adapting mechanical designs, drives and controls previously developed for generic machine tools. This is done through a process of choice and integration which is based principally on empirical criteria and taking into account separately the different aspects and parameters. Hereafter, we present an integrated mechatronic approach which has been adopted to design from the scratch a machine to implement the innovative metal injection moulding (MIM) technology. Its extrusion rate involves the adaptation of the generated trajectories and consequently requires “ad hoc” designs, drives and numerical controls (NC) to enable non standard acceleration (and hence torque) setpoint curves. Overall, the project resulted in an acceptable workspace volume (depending on the number of degrees of freedom of the platform) and allows one to combine the extruder flow rate, the given accuracy and the required working speed (1 m/s). The system is currently used as a test bench for exploring and optimizing the parameter space of a new MIM process. Full article
(This article belongs to the Special Issue Process Innovation in Digital Manufacturing)
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Open AccessArticle Iron Loss Prediction Using Modified IEM-Formula during the Field Weakening for Permanent Magnet Synchronous Machines
Machines 2017, 5(4), 30; doi:10.3390/machines5040030
Received: 20 September 2017 / Revised: 27 November 2017 / Accepted: 29 November 2017 / Published: 5 December 2017
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Abstract
During field weakening operation time (FWOT), the total iron loss rises and affects the accuracy of loss prediction and efficiency, especially if a large range of FWOT exists due to a large voltage drop that was rooted from the resistance of the used
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During field weakening operation time (FWOT), the total iron loss rises and affects the accuracy of loss prediction and efficiency, especially if a large range of FWOT exists due to a large voltage drop that was rooted from the resistance of the used material. Iron loss prediction is widely employed in investigations for a fast electrical machine analysis using 2D finite element analysis (FEA). This paper proposes harmonic loss analytically by a steady-state equivalent circuit with a novel procedure. Consideration of skin effects and iron saturation are utilized in order to examine the accuracy through the relative error distribution in the frequency domain of each model from 50 to 700 Hz. Additionally, this comparative study presents a torque-frequency-field density calculation over each single term of the modified institute of electrical machines formula (IEM-Formula). The proposed analytical calculation is performed using 2D FEA for a classic and modified IEM-Formula along with experimental verifications on a surface-mounted permanent magnet synchronous generator (PMSG) for a wind generation application. Full article
(This article belongs to the Special Issue High Speed Motors and Drives: Design, Challenges and Applications)
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Open AccessArticle Equivalence Analysis of Mass and Inertia for Simulated Space Manipulator Based on Constant Mass
Machines 2017, 5(4), 31; doi:10.3390/machines5040031
Received: 3 November 2017 / Revised: 4 December 2017 / Accepted: 4 December 2017 / Published: 7 December 2017
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Abstract
A simulated space manipulator is designed to verify the reliability of the zero-gravity simulation system, which can avoid the risks of experiments involving the space manipulator in this zero-gravity ground system. To achieve similarity between the simulated and actual space manipulators, the mass,
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A simulated space manipulator is designed to verify the reliability of the zero-gravity simulation system, which can avoid the risks of experiments involving the space manipulator in this zero-gravity ground system. To achieve similarity between the simulated and actual space manipulators, the mass, barycenter, and inertia must be considered. In this study, a counterweight component is designed and an optimization method is used to match the mass parameters of the simulated joints to those of the space joints. In addition, an equivalence method is used to establish the relationship between the torques of these two manipulators. Full article
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Review

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Open AccessReview A Review of Feature Extraction Methods in Vibration-Based Condition Monitoring and Its Application for Degradation Trend Estimation of Low-Speed Slew Bearing
Machines 2017, 5(4), 21; doi:10.3390/machines5040021
Received: 9 August 2017 / Revised: 16 September 2017 / Accepted: 19 September 2017 / Published: 27 September 2017
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Abstract
This paper presents an empirical study of feature extraction methods for the application of low-speed slew bearing condition monitoring. The aim of the study is to find the proper features that represent the degradation condition of slew bearing rotating at very low speed
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This paper presents an empirical study of feature extraction methods for the application of low-speed slew bearing condition monitoring. The aim of the study is to find the proper features that represent the degradation condition of slew bearing rotating at very low speed (≈ 1 r/min) with naturally defect. The literature study of existing research, related to feature extraction methods or algorithms in a wide range of applications such as vibration analysis, time series analysis and bio-medical signal processing, is discussed. Some features are applied in vibration slew bearing data acquired from laboratory tests. The selected features such as impulse factor, margin factor, approximate entropy and largest Lyapunov exponent (LLE) show obvious changes in bearing condition from normal condition to final failure. Full article
(This article belongs to the Special Issue Machinery Condition Monitoring and Industrial Analytics)
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Open AccessReview Rotating Electrical Machine Condition Monitoring Automation—A Review
Machines 2017, 5(4), 24; doi:10.3390/machines5040024
Received: 25 August 2017 / Revised: 3 October 2017 / Accepted: 13 October 2017 / Published: 19 October 2017
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Abstract
We review existing machine condition monitoring techniques and industrial automation for plant-wide condition monitoring of rotating electrical machines. Cost and complexity of a condition monitoring system increase with the number of measurements, so extensive condition monitoring is currently mainly restricted to the situations
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We review existing machine condition monitoring techniques and industrial automation for plant-wide condition monitoring of rotating electrical machines. Cost and complexity of a condition monitoring system increase with the number of measurements, so extensive condition monitoring is currently mainly restricted to the situations where the consequences of poor availability, yield or quality are so severe that they clearly justify the investment in monitoring. There are challenges to obtaining plant-wide monitoring that includes even small machines and non-critical applications. One of the major inhibiting factors is the ratio of condition monitoring cost to equipment cost, which is crucial to the acceptance of using monitoring to guide maintenance for a large fleet of electrical machinery. Ongoing developments in sensing, communication and computation for industrial automation may greatly extend the set of machines for which extensive monitoring is viable. Full article
(This article belongs to the Special Issue Machinery Condition Monitoring and Industrial Analytics)
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