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A Practical Methodology for Accuracy and Quality Evaluation of Structured Light Systems in Automotive Inspection
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Development of an Advanced Wear Simulation Model for a Racing Slick Tire Under Dynamic Acceleration Loading
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Digital Twin-Enabled Adaptive Robotics: Leveraging Large Language Models in Isaac Sim for Unstructured Environments
Journal Description
Machines
Machines
is an international, peer-reviewed, open access journal on machinery and engineering published monthly online by MDPI. The IFToMM is affiliated with Machines and its members receive a discount on the article processing charges.
- Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
- High Visibility: indexed within Scopus, SCIE (Web of Science), Inspec, and other databases.
- Journal Rank: JCR - Q2 (Engineering, Mechanical) / CiteScore - Q1 (Control and Optimization)
- Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 16.9 days after submission; acceptance to publication is undertaken in 2.4 days (median values for papers published in this journal in the first half of 2025).
- Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.
- Journal Cluster of Mechanical Manufacturing and Automation Control: Aerospace, Automation, Drones, Journal of Manufacturing and Materials Processing, Machines, Robotics and Technologies.
Impact Factor:
2.5 (2024);
5-Year Impact Factor:
2.6 (2024)
Latest Articles
A Multifunctional Magnetic Climbing Robot for Pressure Steel Pipe Inspections in Hydropower Plants
Machines 2025, 13(10), 951; https://doi.org/10.3390/machines13100951 (registering DOI) - 15 Oct 2025
Abstract
The inlet pressure steel pipe is an important part of the hydropower unit, and its inspection tasks mainly include cleaning with high-pressure water, surface anti-corrosion layer detection and internal flaw detection. In order to accomplish the above tasks effectively, a multifunctional, non-contact magnetic,
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The inlet pressure steel pipe is an important part of the hydropower unit, and its inspection tasks mainly include cleaning with high-pressure water, surface anti-corrosion layer detection and internal flaw detection. In order to accomplish the above tasks effectively, a multifunctional, non-contact magnetic, tracked climbing robot is presented in this paper. Focusing on the pressure steel pipe inspection tasks, the design of the climbing robot system is given, including the mechanism and control system. By analyzing the slippage and overturning situations, the magnetic attraction constraints for reliable adhesion are obtained, which are used as the basis for designing magnetic adhesion modules. To enable climbing robots to meet the requirement of following the welding seam during the inspections, the improved Deeplabv3+ semantic segmentation method is proposed for welding seam recognition. Experiment results show that the climbing robot can achieve reliable adsorption and flexible movement on the internal face of inlet pressure steel pipe, and the climbing robot can meet the requirements of safety and efficiency for pressure steel pipe inspection processes.
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(This article belongs to the Section Robotics, Mechatronics and Intelligent Machines)
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Open AccessArticle
Dual-Channel Parallel Multimodal Feature Fusion for Bearing Fault Diagnosis
by
Wanrong Li, Haichao Cai, Xiaokang Yang, Yujun Xue, Jun Ye and Xiangyi Hu
Machines 2025, 13(10), 950; https://doi.org/10.3390/machines13100950 (registering DOI) - 15 Oct 2025
Abstract
In recent years, the powerful feature extraction capabilities of deep learning have attracted widespread attention in the field of bearing fault diagnosis. To address the limitations of single-modal and single-channel feature extraction methods, which often result in incomplete information representation and difficulty in
[...] Read more.
In recent years, the powerful feature extraction capabilities of deep learning have attracted widespread attention in the field of bearing fault diagnosis. To address the limitations of single-modal and single-channel feature extraction methods, which often result in incomplete information representation and difficulty in obtaining high-quality fault features, this paper proposes a dual-channel parallel multimodal feature fusion model for bearing fault diagnosis. In this method, the one-dimensional vibration signals are first transformed into two-dimensional time-frequency representations using continuous wavelet transform (CWT). Subsequently, both the one-dimensional vibration signals and the two-dimensional time-frequency representations are fed simultaneously into the dual-branch parallel model. Within this architecture, the first branch employs a combination of a one-dimensional convolutional neural network (1DCNN) and a bidirectional gated recurrent unit (BiGRU) to extract temporal features from the one-dimensional vibration signals. The second branch utilizes a dilated convolutional to capture spatial time–frequency information from the CWT-derived two-dimensional time–frequency representations. The features extracted by both branches were are input into the feature fusion layer. Furthermore, to leverage fault features more comprehensively, a channel attention mechanism is embedded after the feature fusion layer. This enables the network to focus more effectively on salient features across channels while suppressing interference from redundant features, thereby enhancing the performance and accuracy of the dual-branch network. Finally, the fused fault features are passed to a softmax classifier for fault classification. Experimental results demonstrate that the proposed method achieved an average accuracy of 99.50% on the Case Western Reserve University (CWRU) bearing dataset and 97.33% on the Southeast University (SEU) bearing dataset. These results confirm that the suggested model effectively improves fault diagnosis accuracy and exhibits strong generalization capability.
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(This article belongs to the Section Machines Testing and Maintenance)
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Open AccessArticle
Machine Learning-Assisted Synergistic Optimization of 3D Printing Parameters for Enhanced Mechanical Properties of PLA/Boron Nitride Nanocomposites
by
Sundarasetty Harishbabu, Nashmi H. Alrasheedi, Borhen Louhichi, P. S. Rama Sreekanth and Santosh Kumar Sahu
Machines 2025, 13(10), 949; https://doi.org/10.3390/machines13100949 (registering DOI) - 14 Oct 2025
Abstract
Additive manufacturing via fused deposition modeling (FDM) offers a versatile method for fabricating complex polymer parts; however, enhancing their mechanical properties remains a significant challenge, particularly for biopolymers such as polylactic acid (PLA). PLA is widely used in 3D printing due to its
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Additive manufacturing via fused deposition modeling (FDM) offers a versatile method for fabricating complex polymer parts; however, enhancing their mechanical properties remains a significant challenge, particularly for biopolymers such as polylactic acid (PLA). PLA is widely used in 3D printing due to its biodegradability and ease of processing, but its relatively low mechanical strength and impact resistance limit its broader applications. This study explores the reinforcement of PLA with boron nitride nanoplatelets (BNNPs) to improve its mechanical properties. This study also aims to optimize key FDM process parameters, such as reinforcement content, nozzle temperature, printing speed, layer thickness, and sample orientation, using a Taguchi L27 design. Results show that the addition of 0.04 wt.% BNNP significantly improves the mechanical properties of PLA, enhancing tensile strength by 44.2%, Young’s modulus by 45.5%, and impact strength by over 500% compared to pure PLA. Statistical analysis (ANOVA) reveals that printing speed and nozzle temperature are the primary factors affecting tensile strength and Young’s modulus, while impact strength is primarily influenced by nozzle temperature and reinforcement content. Machine learning models, such as CatBoost and Gaussian process regression, predict mechanical properties with high accuracy (R2 > 0.98), providing valuable insights for tailoring PLA/BNNP composites and optimizing FDM process parameters. This integrated approach presents a promising path for developing high-performance, sustainable nanocomposites for advanced additive manufacturing applications.
Full article
(This article belongs to the Special Issue Advanced Manufacturing Processes and Technologies: Trends and Innovations)
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Open AccessArticle
Identification of Turbocharger Noise Sources Taking into Account Design Operating Conditions
by
Jozef Doman, Pavel Novotný and Vladimir Chmelko
Machines 2025, 13(10), 948; https://doi.org/10.3390/machines13100948 (registering DOI) - 14 Oct 2025
Abstract
The paper describes in detail the creation of selected aerodynamic sound sources created by the centrifugal compressor of the turbocharger in operating modes. The description of the creation of aerodynamic sources focuses on the operation of the compressor in a stable area of
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The paper describes in detail the creation of selected aerodynamic sound sources created by the centrifugal compressor of the turbocharger in operating modes. The description of the creation of aerodynamic sources focuses on the operation of the compressor in a stable area of the characteristic. The analysis is based on a detailed survey of selected aerodynamic sources, mainly vortex shedding, TCN, and buzz-saw phenomena, with a focus on the mechanism of the source and the possibility of identifying the source in the frequency spectrum. Based on the survey, the selected sound sources characterize the assumed frequency ranges at which the sources are estimated to originate. Additional source conditions identified in the survey can be used to develop a methodology for identifying aerodynamic sound sources. In the case of aerodynamic sources of a centrifugal compressor, it was necessary to develop an experimental numerical methodology for their identification with regard to the operating condition of the compressor. The result of the proposed procedure is an algorithm that will enable the identification of aerodynamic sound sources in the frequency spectrum with respect to the operating state of the compressor.
Full article
(This article belongs to the Special Issue Nonlinear Dynamics, Vibration Monitoring and Fault Diagnostics in Rotating Systems)
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Open AccessSystematic Review
Hypotheses in Opportunistic Maintenance Modeling: A Critical and Systematic Literature Review
by
Lucas Equeter, Phuc Do, Lorenzo Colantonio, Luca A. Tiberi, Pierre Dehombreux and Benoît Iung
Machines 2025, 13(10), 947; https://doi.org/10.3390/machines13100947 (registering DOI) - 14 Oct 2025
Abstract
Because they account for realistic effects in opportunistic maintenance modeling, dependency hypotheses are extremely diverse in the literature. Despite recent reviews, a clear view of the dependency hypotheses is currently missing in the literature, especially regarding component interactions, resource constraints and human factors.
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Because they account for realistic effects in opportunistic maintenance modeling, dependency hypotheses are extremely diverse in the literature. Despite recent reviews, a clear view of the dependency hypotheses is currently missing in the literature, especially regarding component interactions, resource constraints and human factors. In this paper, we provide a conceptual background on dependence modeling and the notion of maintenance opportunity. Then, a critical systematic literature review, following the PRISMA guidelines, is carried out, focusing on the current hypotheses in opportunistic maintenance, including component interactions, workers’ skills and resource constraints, economic dependence and optimization objectives. The different dependence types are identified and defined, and their presence in the literature is quantified. The included papers in this review ( ) were selected on the basis of relevance to the research questions from the Web of Science, Scopus and Google Scholar databases. Exclusion criteria were set, related to the year of publication (from 2000) and language (limited to French or English), and inclusion criteria required the paper to cover modeling, simulating or reviewing literature related to opportunistic maintenance with dependencies. The results show that economic dependence is mostly modeled by sharing downtime or set-up costs. The objective function for optimization is mostly found to be the economic cost of maintenance, with concerningly little consideration for environmental indicators. These results are finally discussed in light of advances in predictive analytics and current challenges in the sustainability of industrial processes. Further developments should consider including the social and environmental aspects of sustainability in the dependencies, but also look into the benefits that predictive analytics can bring to opportunistic maintenance. The variety of modeling assumptions and dependences presented in the literature does not always allow comparing the results of the models.
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(This article belongs to the Section Machines Testing and Maintenance)
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Open AccessReview
A Review of Artificial Intelligence-Driven Active Vibration and Noise Control
by
Zongkang Jiang, Hongtao Xue, Huiyu Yue, Xiaoyi Bao, Junwei Zhu, Xuan Wang and Liang Zhang
Machines 2025, 13(10), 946; https://doi.org/10.3390/machines13100946 (registering DOI) - 13 Oct 2025
Abstract
The core objective of Active Vibration and Noise Control (AVNC) is to enhance system performance by generating real-time counter-phase signals of equal amplitude to cancel out vibration and noise interference from mechanical or structural systems. As the demand for low-noise, low-vibration environments grows
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The core objective of Active Vibration and Noise Control (AVNC) is to enhance system performance by generating real-time counter-phase signals of equal amplitude to cancel out vibration and noise interference from mechanical or structural systems. As the demand for low-noise, low-vibration environments grows in fields such as new energy vehicles (NEVs), aerospace, and high-precision manufacturing, traditional AVNC methods—which rely on precise linear models and have poor adaptability to nonlinear and time-varying conditions—struggle to meet the dynamic requirements of complex engineering scenarios. However, with advancements in artificial intelligence (AI) technology, AI-driven Active Vibration and Noise Control (AI-AVNC) technology has garnered significant attention from both industry and academia. Based on a thorough investigation into the state-of-the-art AI-AVNC methods, this survey has made the following contributions: (1) Introducing the theoretical foundations of AVNC and its historical development; (2) Classifying existing AI-AVNC methods from the perspective of control strategies; (3) Analyzing engineering applications of AI-AVNC; (4) Discussing current technical challenges and future development trends of AI-AVNC.
Full article
(This article belongs to the Special Issue New Journeys in Vehicle System Dynamics and Control)
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Open AccessArticle
Phase-Aware Complex-Spectrogram Autoencoder for Vibration Preprocessing: Fault-Component Separation via Input-Phasor Orthogonality Regularization
by
Seung-yeol Yoo, Ye-na Lee, Jae-chul Lee, Se-yun Hwang, Jae-yun Lee and Soon-sup Lee
Machines 2025, 13(10), 945; https://doi.org/10.3390/machines13100945 (registering DOI) - 13 Oct 2025
Abstract
We propose a phase-aware complex-spectrogram autoencoder (AE) for preprocessing raw vibration signals of rotating electrical machines. The AE reconstructs normal components and separates fault components as residuals, guided by an input-phasor phase-orthogonality regularization that defines parallel/orthogonal residuals with respect to the local signal
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We propose a phase-aware complex-spectrogram autoencoder (AE) for preprocessing raw vibration signals of rotating electrical machines. The AE reconstructs normal components and separates fault components as residuals, guided by an input-phasor phase-orthogonality regularization that defines parallel/orthogonal residuals with respect to the local signal phase. We use a U-Net-based AE with a mask-bias head to refine local magnitude and phase. Decisions are based on residual features—magnitude/shape, frequency distribution, and projections onto the normal manifold. Using the AI Hub open dataset from field ventilation motors, we evaluate eight representative motor cases (2.2–5.5 kW: misalignment, unbalance, bearing fault, belt looseness). The preprocessing yielded clear residual patterns (low-frequency floor rise, resonance-band peaks, harmonic-neighbor spikes), and achieved an area under the receiver operating characteristic curve (ROC-AUC) = 0.998–1.000 across eight cases, with strong leave-one-file-out generalization and good calibration (expected calibration error (ECE) ≤ 0.023). The results indicate that learning to remove normal structure while enforcing phase consistency provides an unsupervised front-end that enhances fault evidence while preserving interpretability on field data.
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(This article belongs to the Section Machines Testing and Maintenance)
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Open AccessArticle
Automatic Determination of the Denavit–Hartenberg Parameters for the Forward Kinematics of All Serial Robots: Novel Kinematics Toolbox
by
Haydar Karhan and Zafer Bingül
Machines 2025, 13(10), 944; https://doi.org/10.3390/machines13100944 (registering DOI) - 13 Oct 2025
Abstract
Traditionally, the determination of the Denavit–Hartenberg (DH) parameters for serial robotic manipulators is a manual process that depends on manufacturer documentation or user-defined conventions, often leading to inefficiency and ambiguity in DH frame placement and parameters. This study introduces a universal and systematic
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Traditionally, the determination of the Denavit–Hartenberg (DH) parameters for serial robotic manipulators is a manual process that depends on manufacturer documentation or user-defined conventions, often leading to inefficiency and ambiguity in DH frame placement and parameters. This study introduces a universal and systematic methodology for automatically deriving DH parameters directly from a robot’s zero configuration, using only the geometric relationships between consecutive joint axes. The approach was implemented in a MATLAB-based kinematics toolbox capable of computing both the classical and modified DH parameters. In addition to parameter extraction, the toolbox integrates workspace visualization, manipulability and dexterity analysis, and a slicing and alpha-shape algorithm for accurate workspace volume computation. Validation was conducted on multiple industrial robots by comparing the extracted parameters with the manufacturer data and the RoboDK models. Benchmark studies confirmed the accuracy of the volume estimation, yielding an absolute percentage error of less than 4%. While the current implementation relies on RoboDK models for verification and requires the manual tuning of the alpha-shape parameter, the toolbox provides a reproducible and extensible framework for research, education, and robot design.
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(This article belongs to the Special Issue Control and Mechanical System Engineering, 2nd Edition)
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Open AccessArticle
Encoding Multivariate Time Series of Gas Turbine Data as Images to Improve Fault Detection Reliability
by
Enzo Losi, Mauro Venturini, Lucrezia Manservigi and Giovanni Bechini
Machines 2025, 13(10), 943; https://doi.org/10.3390/machines13100943 (registering DOI) - 13 Oct 2025
Abstract
The monitoring and diagnostics of energy equipment aim to detect anomalies in time series data in order to support predictive maintenance and avoid unplanned shutdowns. Thus, the paper proposes a novel methodology that utilizes sequence-to-image transformation methods to feed Convolutional Neural Networks (CNNs)
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The monitoring and diagnostics of energy equipment aim to detect anomalies in time series data in order to support predictive maintenance and avoid unplanned shutdowns. Thus, the paper proposes a novel methodology that utilizes sequence-to-image transformation methods to feed Convolutional Neural Networks (CNNs) for diagnostic purposes. Multivariate time series taken from real gas turbines are transformed by using two methods. We study two CNN architectures, i.e., VGG-19 and SqueezeNet. The investigated anomaly is the spike fault. Spikes are implanted in field multivariate time series taken during normal operation of ten gas turbines and composed of twenty gas path measurements. Six fault scenarios are simulated. For each scenario, different combinations of fault parameters are considered. The main novel contribution of this study is the development of a comprehensive framework, which starts from time series transformation and ends up with a diagnostic response. The potential of CNNs for image recognition is applied to the gas path field measurements of a gas turbine. A hard-to-detect type of fault (i.e., random spikes of different magnitudes and frequencies of occurrence) was implanted in a seemingly real-world fashion. Since spike detection is highly challenging, the proposed framework has both scientific and industrial relevance. The extended and thorough analyses unequivocally prove that CNNs fed with images are remarkably more accurate than TCN models fed with raw time series data, with values higher than 93% if the number of implanted spikes is 10% of the total data and a gain in accuracy of up to 40% in the most realistic scenario.
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(This article belongs to the Special Issue Advanced Techniques for Fault Detection, Diagnosis, and Prognostics in Machinery)
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Open AccessArticle
A Comprehensive Tooth Surface Modification Method for Harmonic Drive by Changing the Radial Deformation Coefficient
by
Feng Yin, Zhezhen Cao, Bingquan Lu, Yuansheng Zhou, Shenghui Wang and Jinyuan Tang
Machines 2025, 13(10), 942; https://doi.org/10.3390/machines13100942 (registering DOI) - 13 Oct 2025
Abstract
The tooth surface geometry of harmonic gears directly affects the transmission accuracy and service life. Traditional design methods may cause tooth profile distortion when changing the radial deformation coefficient, which limits their application. This paper proposes a comprehensive tooth surface modification method that
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The tooth surface geometry of harmonic gears directly affects the transmission accuracy and service life. Traditional design methods may cause tooth profile distortion when changing the radial deformation coefficient, which limits their application. This paper proposes a comprehensive tooth surface modification method that changes the radial deformation coefficient on the basis of traditional design methods. Firstly, the meshing trajectories and corresponding tooth profiles of gear teeth under different radial deformation coefficients are calculated and analyzed based on the rack approximation method. Secondly, a calculation method is proposed to eliminate the tooth profile distortion caused by changing the radial deformation coefficient, which not only expands the application of the rack approximation method but also eliminates interference during the meshing process. Subsequently, a comprehensive tooth surface modification method is proposed with the aim of increasing contact area and contact ratio, as well as reducing contact stress. Compared to traditional modification, it requires less material removal, which is beneficial for increasing the tooth strength. Furthermore, a finite element simulation model of a harmonic drive is established, and the tooth surface and contact performance of harmonic gears under three different radial deformation coefficients are designed and analyzed, verifying the effectiveness of the proposed tooth surface design method.
Full article
(This article belongs to the Section Machine Design and Theory)
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Open AccessArticle
Research on Quasi-Static Transmission Error Measurement of Spur Gears Based on the Acceleration Method
by
Chengcheng Ji, Jian Zhang, Jiaxin Jian, Chuanmao Lv and Zhengminqing Li
Machines 2025, 13(10), 941; https://doi.org/10.3390/machines13100941 (registering DOI) - 13 Oct 2025
Abstract
Transmission error (TE) is an important parameter in gear dynamics that has a direct impact on the vibration and noise of gears. Under quasi-static conditions, gear elastic deformation and assembly errors amplify with increasing load, potentially contributing to noise and vibration. This paper
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Transmission error (TE) is an important parameter in gear dynamics that has a direct impact on the vibration and noise of gears. Under quasi-static conditions, gear elastic deformation and assembly errors amplify with increasing load, potentially contributing to noise and vibration. This paper presents a novel method for measuring the quasi-static transmission error (QSTE) of spur gears under quasi-static conditions. In particular, the study investigates the relationship between quasi-static transmission error, elastic deformation transmission error, and gear tangential acceleration. Gear elastic deformation transmission error was calculated from experimental data obtained with single-point, symmetrical dual-point, and orthogonal four-point configurations of tangential acceleration sensors. The orthogonal four-point sensor configuration greatly improves measurement accuracy when compared to theoretical values derived from material mechanics calculations. A dedicated on-machine acquisition system for spur gear tangential acceleration was constructed. Tangential acceleration tests were conducted across varying loads and rotational speeds. The acquired data underwent filtering and integration processing in order to obtain gear elastic deformation and quasi-static transmission error. The feasibility of the acceleration approach for measuring both gear elastic deformation and quasi-static transmission error is confirmed by a comparative analysis of the acceleration method results with transmission errors obtained via material mechanics calculations and magnetic grating detection.
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(This article belongs to the Section Machine Design and Theory)
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Open AccessArticle
Integration of Industrial Internet of Things (IIoT) and Digital Twin Technology for Intelligent Multi-Loop Oil-and-Gas Process Control
by
Ali Saleh Allahloh, Mohammad Sarfraz, Atef M. Ghaleb, Abdulmajeed Dabwan, Adeeb A. Ahmed and Adel Al-Shayea
Machines 2025, 13(10), 940; https://doi.org/10.3390/machines13100940 (registering DOI) - 13 Oct 2025
Abstract
The convergence of Industrial Internet of Things (IIoT) and digital twin technology offers new paradigms for process automation and control. This paper presents an integrated IIoT and digital twin framework for intelligent control of a gas–liquid separation unit with interacting flow, pressure, and
[...] Read more.
The convergence of Industrial Internet of Things (IIoT) and digital twin technology offers new paradigms for process automation and control. This paper presents an integrated IIoT and digital twin framework for intelligent control of a gas–liquid separation unit with interacting flow, pressure, and differential pressure loops. A comprehensive dynamic model of the three-loop separator process is developed, linearized, and validated. Classical stability analyses using the Routh–Hurwitz criterion and Nyquist plots are employed to ensure stability of the control system. Decentralized multi-loop proportional–integral–derivative (PID) controllers are designed and optimized using the Integral Absolute Error (IAE) performance index. A digital twin of the separator is implemented to run in parallel with the physical process, synchronized via a Kalman filter to real-time sensor data for state estimation and anomaly detection. The digital twin also incorporates structured singular value ( ) analysis to assess robust stability under model uncertainties. The system architecture is realized with low-cost hardware (Arduino Mega 2560, MicroMotion Coriolis flowmeter, pneumatic control valves, DAC104S085 digital-to-analog converter, and ENC28J60 Ethernet module) and software tools (Proteus VSM 8.4 for simulation, VB.Net 2022 version based human–machine interface, and ML.Net 2022 version for predictive analytics). Experimental results demonstrate improved control performance with reduced overshoot and faster settling times, confirming the effectiveness of the IIoT–digital twin integration in handling loop interactions and disturbances. The discussion includes a comparative analysis with conventional control and outlines how advanced strategies such as model predictive control (MPC) can further augment the proposed approach. This work provides a practical pathway for applying IIoT and digital twins to industrial process control, with implications for enhanced autonomy, reliability, and efficiency in oil and gas operations.
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(This article belongs to the Special Issue Digital Twins Applications in Manufacturing Optimization)
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Open AccessArticle
Self-Regulating Fuzzy-LQR Control of an Inverted Pendulum System via Adaptive Hyperbolic Error Modulation
by
Omer Saleem, Jamshed Iqbal and Soltan Alharbi
Machines 2025, 13(10), 939; https://doi.org/10.3390/machines13100939 (registering DOI) - 12 Oct 2025
Abstract
This study introduces an innovative self-regulating intelligent optimal balancing control framework for inverted pendulum-type mechatronic platforms, designed to enhance reference tracking accuracy and improve disturbance rejection capability. The control procedure is synthesized by synergistically integrating a baseline Linear Quadratic Regulator (LQR) with a
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This study introduces an innovative self-regulating intelligent optimal balancing control framework for inverted pendulum-type mechatronic platforms, designed to enhance reference tracking accuracy and improve disturbance rejection capability. The control procedure is synthesized by synergistically integrating a baseline Linear Quadratic Regulator (LQR) with a fuzzy controller via a customized linear decomposition function (LDF). The LDF dissociates and transforms the LQR control law into compounded state tracking error and tracking error derivative variables that are eventually used to drive the fuzzy controller. The principal contribution of this study lies in the adaptive modulation of these compounded variables using reconfigurable tangent hyperbolic functions driven by the cubic power of the error signals. This nonlinear preprocessing of the input variables selectively amplifies large errors while attenuating small ones, thereby improving robustness and reducing oscillations. Moreover, a model-free online self-tuning law dynamically adjusts the variation rates of the hyperbolic functions through dissipative and anti-dissipative terms of the state errors, enabling autonomous reconfiguration of the nonlinear preprocessing layer. This dual-level adaptation enhances the flexibility and resilience of the controller under perturbations. The robustness of the designed controller is substantiated via tailored experimental trials conducted on the Quanser rotary pendulum platform. Comparative results show that the prescribed scheme reduces pendulum angle variance by 41.8%, arm position variance by 34.6%, and average control energy by 28.3% relative to the baseline LQR, while outperforming conventional fuzzy-LQR by similar margins. These results show that the prescribed controller significantly enhances disturbance rejection and tracking accuracy, thereby offering a numerically superior control of inverted pendulum systems.
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(This article belongs to the Special Issue Mechatronic Systems: Developments and Applications)
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Open AccessArticle
Promoting the Green Transformation of Traditional Ships in Anhui Province: A Model Prediction Cost Analysis Algorithm for a New Electrification Transformation Scheme Using Lithium Iron Phosphate Battery
by
Xiaoqing Zhou, Risha Na and Jun Tao
Machines 2025, 13(10), 938; https://doi.org/10.3390/machines13100938 (registering DOI) - 11 Oct 2025
Abstract
Promoting the green transformation of traditional diesel-powered ships is crucial for achieving carbon peaking and carbon neutrality goals. This study focuses on diesel-engine ships operating in the inland river areas of Anhui Province, China. It proposes two electrification retrofit schemes based mainly on
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Promoting the green transformation of traditional diesel-powered ships is crucial for achieving carbon peaking and carbon neutrality goals. This study focuses on diesel-engine ships operating in the inland river areas of Anhui Province, China. It proposes two electrification retrofit schemes based mainly on lithium iron phosphate (LIP) batteries: full electrification and diesel-engine redundancy. The economic and environmental impacts of these schemes are analyzed and compared with those of conventional diesel-powered ships. A cost prediction algorithm based on model prediction is proposed, supported by a mathematical model for cost analysis. Results indicate that for electric tankers to become economically viable, battery costs must decrease through yearly improvements in energy density and reduced degradation rates. Additionally, government support is essential, such as raising carbon prices and providing subsidies—either an annual operational subsidy of CNY 80,000 or an initial construction subsidy of CNY 500,000. The study concludes that continued advances in battery technology, together with policy and financial support, will accelerate the large-scale electrification of ships.
Full article
(This article belongs to the Special Issue Advanced Power Electronic Technologies in Electric Drive Systems, 2nd Edition)
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Open AccessArticle
Development and Balancing Control of Control Moment Gyroscope (CMG) Unicycle–Legged Robot
by
Seungchul Shin, Minjun Choi, Seongmin Ahn, Seongyong Hur, David Kim and Dongil Choi
Machines 2025, 13(10), 937; https://doi.org/10.3390/machines13100937 - 10 Oct 2025
Abstract
A wheeled–legged robot has the advantage of stable and agile movement on flat ground and an excellent ability to overcome obstacles. However, when faced with a narrow footprint, there is a limit to its ability to move. We developed the control moment gyroscope
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A wheeled–legged robot has the advantage of stable and agile movement on flat ground and an excellent ability to overcome obstacles. However, when faced with a narrow footprint, there is a limit to its ability to move. We developed the control moment gyroscope (CMG) unicycle–legged robot to solve this problem. A scissored pair of CMGs was applied to control the roll balance, and the pitch balance was modeled as a double-inverted pendulum. We performed Linear Quadratic Regulator (LQR) control and model predictive control (MPC) in a system in which the control systems in the roll and pitch directions were separated. We also devised a method for controlling the rotation of the robot in the yaw direction using torque generated by the CMG, and the performance of these controllers was verified in the Gazebo simulator. In addition, forward driving control was performed to verify mobility, which is the main advantage of the wheeled–legged robot; it was confirmed that this control enabled the robot to pass through a narrow space of 0.15 m. Before implementing the verified controllers in the real world, we built a CMG test platform and confirmed that balancing control was maintained within .
Full article
(This article belongs to the Special Issue Advances in Robot Kinematics and Dynamics: Innovations, Control Strategies, and Practical Applications)
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Open AccessArticle
Prediction and Optimization of Interference Fit Level in Slug Riveted Structure with Deep Learning Enhanced Genetic Algorithm
by
Kanghe Yan, Lichao Wan, Nana Hui, Donghe Shan, Yang Zhao and Zhengping Chang
Machines 2025, 13(10), 936; https://doi.org/10.3390/machines13100936 - 10 Oct 2025
Abstract
The interference fit connection with slug rivets is widely used in aircraft assembly, and an appropriate interference value is vital for aircraft structural integrity. This study proposed a prediction–optimization framework that a deep neural network (DNN) surrogate was trained on a parametric finite
[...] Read more.
The interference fit connection with slug rivets is widely used in aircraft assembly, and an appropriate interference value is vital for aircraft structural integrity. This study proposed a prediction–optimization framework that a deep neural network (DNN) surrogate was trained on a parametric finite element dataset to regress four interference measurements (G1–G4), and the trained DNN was embedded into a genetic algorithm (GA) to search process parameters that meet prescribed target interference. An orthogonal design with range analysis was employed to rank factor importance and provide interpretable trends, while finite element model (FEM) re-runs were used for validation. Compared with support vector regression, random-forest regression, and Bayesian regression, the DNN demonstrated superior fitting accuracy and a more favorable error distribution on held-out data. GA solutions obtained using the DNN surrogate achieved the target interference with a maximum relative deviation of 9.75%, confirming the effectiveness of the proposed workflow for rapid, physics-consistent interference control. The contributions of the study were as follows: (i) an end-to-end, quick-response, reproducible FEM→DNN→GA pipeline for slug-rivet interference; (ii) quantitative factor ranking with mechanistic interpretation; and (iii) minute-scale parameter optimization suitable for engineering deployment.
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(This article belongs to the Special Issue Advanced Manufacturing and Assembly Technologies for Aerospace Production Systems)
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Open AccessArticle
PSO-LQR Control of ISD Suspension for Vehicle Coupled with Bridge Considering General Boundary Conditions
by
Buyun Zhang, Shipeng Dai, Yunshun Zhang and Chin An Tan
Machines 2025, 13(10), 935; https://doi.org/10.3390/machines13100935 - 10 Oct 2025
Abstract
With the rapid development of transportation infrastructure, bridges increasingly face prominent issues of dynamic response and fatigue damage induced by vehicle–bridge interaction (VBI). To effectively suppress the coupled vibrations and enhance both vehicle ride comfort and bridge service life, this paper proposes an
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With the rapid development of transportation infrastructure, bridges increasingly face prominent issues of dynamic response and fatigue damage induced by vehicle–bridge interaction (VBI). To effectively suppress the coupled vibrations and enhance both vehicle ride comfort and bridge service life, this paper proposes an active inerter-spring-damper (ISD) suspension system based on Particle Swarm Optimization (PSO) algorithm and Linear Quadratic Regulator (LQR) control. By establishing a VBI model considering general boundary conditions and employing the modal superposition method to solve the system response, an LQR controller is designed for multi-objective optimization targeting the vehicle body acceleration, suspension dynamic travel, and tire dynamic load. To further improve control performance, the PSO algorithm is utilized to globally optimize the LQR weighting matrices. Numerical simulation results demonstrate that, compared to passive suspension and unoptimized LQR active suspension, the PSO-LQR control strategy significantly reduces vertical body acceleration and tire dynamic load, while also improving the convergence and stability of the suspension dynamic travel. This research provides a new insight into the control method for VBI systems, possessing both theoretical and practical engineering application value.
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(This article belongs to the Special Issue Advances in Vehicle Suspension System Optimization and Control)
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Open AccessArticle
Design and Optimization of Lightweight Electromagnetic Valves for High-Altitude Latex Balloons
by
Xiaoran Li, Donghui Zhang, Qiguang Yang, Zihao Wang and Chen Chen
Machines 2025, 13(10), 934; https://doi.org/10.3390/machines13100934 - 10 Oct 2025
Abstract
To address the altitude control requirements of high-altitude latex balloons, this paper proposes a novel lightweight electromagnetically actuated valve design. The valve employs a permanent magnet–electromagnet–spring composite structure to achieve rapid opening/closing motions through electromagnetic force control, enabling precise regulation of balloon gas
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To address the altitude control requirements of high-altitude latex balloons, this paper proposes a novel lightweight electromagnetically actuated valve design. The valve employs a permanent magnet–electromagnet–spring composite structure to achieve rapid opening/closing motions through electromagnetic force control, enabling precise regulation of balloon gas venting. 3D electromagnetic field simulations were conducted to validate the magnetic flux density distribution, while computational fluid dynamics (CFD) simulations based on the Reynolds-averaged Navier–Stokes equations were employed to evaluate the valve’s aerodynamic characteristics. The CFD results confirmed stable venting performance, with near-linear flow–pressure relationships and localized jet structures that support reliable operation under stratospheric conditions. A multidisciplinary optimization framework was further applied to achieve a lightweight structural design of critical components. Experimental results demonstrate that the optimized valve achieves a total mass of 984.69 g with an actuation force of 15.263 N, maintaining stable performance across a temperature range of −60 °C to 25 °C. This study provides an innovative and systematically validated solution for micro-valve design in lighter-than-air vehicles.
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(This article belongs to the Special Issue Advanced Aircraft Aerodynamics, Flight Stability, Stabilization and Control of Flying Vehicles)
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Open AccessArticle
Adaptive Trigger Compensation Neural Network for PID Tuning in Virtual Autopilot Heading Control
by
Yutong Zhou and Shan Fu
Machines 2025, 13(10), 933; https://doi.org/10.3390/machines13100933 - 10 Oct 2025
Abstract
Virtual commands are significant to model human–computer interactions in autopilot flight missions. However, the huge system hysteresis makes it difficult for proportional–integral–derivative (PID) algorithms to generate the commands that promise better flight convergence. An adaptive trigger compensation neural network method is proposed to
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Virtual commands are significant to model human–computer interactions in autopilot flight missions. However, the huge system hysteresis makes it difficult for proportional–integral–derivative (PID) algorithms to generate the commands that promise better flight convergence. An adaptive trigger compensation neural network method is proposed to dynamically tune the PID parameters, simulating the process of deciding virtual heading commands and performing heading adjustments for virtual pilots. The method consists of trigger filtering, dynamic updating, and compensation synthesis. First, the necessary historical errors are adaptively selected by the threshold trigger filter for better error utilization. Second, error-based initialization is introduced in the neural network PID update process to improve adaptiveness in the initial settings of PID parameters. Third, the parameters are synthesized via error compensation to compute virtual heading commands for acquiring more convergent flight trajectories. The adaptive filter, error-based initialization, and compensation are important to improve the backward propagation neural network in tuning PID parameters. The results demonstrate the advance of the method in simulating heading adjustment behaviors and reducing flight trajectory deviation and fluctuation. The adaptive trigger compensation neural network can enhance the convergent performance of the PID algorithm during autopilot flight scenarios.
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(This article belongs to the Special Issue Control and Mechanical System Engineering, 2nd Edition)
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Open AccessArticle
Profit-Oriented Multi-Objective Dynamic Flexible Job Shop Scheduling with Multi-Agent Framework Under Uncertain Production Orders
by
Qingyao Ma, Yao Lu and Huawei Chen
Machines 2025, 13(10), 932; https://doi.org/10.3390/machines13100932 - 9 Oct 2025
Abstract
In the highly competitive manufacturing environment, customers are increasingly demanding punctual, flexible, and customized deliveries, compelling enterprises to balance profit, energy efficiency, and production performance while seeking new scheduling methods to enhance dynamic responsiveness. Although deep reinforcement learning (DRL) has made progress in
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In the highly competitive manufacturing environment, customers are increasingly demanding punctual, flexible, and customized deliveries, compelling enterprises to balance profit, energy efficiency, and production performance while seeking new scheduling methods to enhance dynamic responsiveness. Although deep reinforcement learning (DRL) has made progress in dynamic flexible job shop scheduling, existing research has rarely addressed profit-oriented optimization. To tackle this challenge, this paper proposes a novel multi-objective dynamic flexible job shop scheduling (MODFJSP) model that aims to maximize net profit and minimize makespan on the basis of traditional FJSP. The model incorporates uncertainties such as new job insertions, fluctuating due dates, and high-profit urgent jobs, and establishes a multi-agent collaborative framework consisting of “job selection–machine assignment.” For the two types of agents, this paper proposes adaptive state representations, reward functions, and variable action spaces to achieve the dual optimization objectives. The experimental results show that the double deep Q-network (DDQN), within the multi-agent cooperative framework, outperforms PPO, DQN, and classical scheduling rules in terms of solution quality and robustness. It achieves superior performance on multiple metrics such as IGD, HV, and SC, and generates bi-objective Pareto frontiers that are closer to the ideal point. The results demonstrate the effectiveness and practical value of the proposed collaborative framework for solving MODFJSP.
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(This article belongs to the Section Industrial Systems)
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