Machines

11 pages, 2369 KB

Open AccessArticle

Experimental Evaluation of a Line-Start Consequent-Pole Surface Permanent-Magnet Motor with Simple Rotor Design Strategies for Performance Improvement

by Yuichi Yokoi, Yasuhiro Miyamoto and Tsuyoshi Higuchi

Machines 2025, 13(11), 1003; https://doi.org/10.3390/machines13111003 (registering DOI) - 31 Oct 2025

Abstract

The line-start permanent-magnet (LSPM) motor combines the direct-on-line starting of induction motors with the high efficiency of permanent-magnet (PM) synchronous motors, but conventional interior PM designs are difficult to manufacture and surface PM (SPM) designs often suffer from limited starting torque and reduced [...] Read more.

The line-start permanent-magnet (LSPM) motor combines the direct-on-line starting of induction motors with the high efficiency of permanent-magnet (PM) synchronous motors, but conventional interior PM designs are difficult to manufacture and surface PM (SPM) designs often suffer from limited starting torque and reduced efficiency. This paper investigates consequent-pole SPM designs, in which the number of magnets is reduced by half while maintaining equal magnet volume, enabling simple rotor construction and improved starting performance. A prototype is manufactured and tested, confirming smooth synchronization under load. Efficiency is constrained by the non-sinusoidal flux distribution of the consequent-pole structure. Rotor design strategies enlarging the air gap near the iron poles are analyzed, and a finite element method analysis shows improved torque and efficiency without loss of starting capability. Full article

(This article belongs to the Section Electrical Machines and Drives)

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20 pages, 2503 KB

Open AccessArticle

Towards Digital Transformation in SMEs: A Custom Software Solution for Shopfloor–ERP Integration

by Bárbara Amaro, Abílio Borges, Angela Semitela and António Completo

Machines 2025, 13(11), 1002; https://doi.org/10.3390/machines13111002 (registering DOI) - 31 Oct 2025

Abstract

The increasing complexity of mechanical manufacturing demands intelligent, integrated solutions to maintain high levels of precision, efficiency, and traceability. While ERP systems provide centralized management for core business functions, they often fall short in addressing operational-level workflows on the shopfloor. This paper presents [...] Read more.

The increasing complexity of mechanical manufacturing demands intelligent, integrated solutions to maintain high levels of precision, efficiency, and traceability. While ERP systems provide centralized management for core business functions, they often fall short in addressing operational-level workflows on the shopfloor. This paper presents the development and implementation of GIP (Gestão Integrada de Produção—Integrated Production Management), a custom software solution designed to bridge this gap for a small-to-medium enterprise (SME) specializing in precision mechanical components. GIP automates manual tasks such as technical drawing validation, file management, and part tracking, significantly reducing approval times and human error while enhancing traceability through unique DataMatrix part marking and centralized data logging. Developed with a modular, user-centered design using C# and SQL Server, the system integrates seamlessly with existing ERP infrastructure, following Industry 4.0 principles. Its deployment resulted in quantifiable improvements in productivity, data security, interdepartmental communication, and project delivery times. The success of GIP underscores the benefits of complementing ERP platforms with task-specific tools tailored to real user workflows. This approach aligns with smart manufacturing trends such as digital threads and digital twins, laying the groundwork for future enhancements in predictive maintenance and real-time analytics. GIP demonstrates how agile, scalable digital tools can drive competitiveness in modern industrial environments. Full article

(This article belongs to the Section Automation and Control Systems)

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22 pages, 8305 KB

Open AccessArticle

Investigation on the Use of 2D-DOST on Time–Frequency Representations of Stray Flux Signals for Induction Motor Fault Classification Using a Lightweight CNN Model

by Geovanni Díaz-Saldaña, Luis Morales-Velazquez, Vicente Biot-Monterde and José Alfonso Antonino-Daviu

Machines 2025, 13(11), 1001; https://doi.org/10.3390/machines13111001 (registering DOI) - 31 Oct 2025

Abstract

Condition monitoring and fault detection in induction motors (IMs) are priorities in the industrial environment to secure safe conditions for the processes and production. Convolutional Neural Networks (CNNs) are gaining interest in these tasks as they allow automatic extraction of features from the [...] Read more.

Condition monitoring and fault detection in induction motors (IMs) are priorities in the industrial environment to secure safe conditions for the processes and production. Convolutional Neural Networks (CNNs) are gaining interest in these tasks as they allow automatic extraction of features from the inputs, sometimes Time–Frequency Distributions (TFDs) obtained with various transforms, directly into large models for data classification. This work presents a proposal for the application of a widely used texture analysis tool in the medical field, the 2D Discrete Orthonormal Stockwell Transform (2D-DOST), to improve the accuracy of a lightweight CNN when using different TFDs and comparing the results to the use of the TFDs in RGB and grayscale. The results show that the use of the 2D-DOST improves the classification accuracy in a two to five percent range for all motor conditions under study, while having minimal variations to the training times when compared to RGB or grayscale images, opening the possibility for the use of image processing tools on TFDs to improve automatic feature extraction while using small CNN models. Full article

(This article belongs to the Section Electrical Machines and Drives)

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50 pages, 2867 KB

Open AccessReview

Literature Review on Fault Mechanism Analysis and Diagnosis Methods for Main Pump Systems

by Wensheng Ma, Shoutao Ma, Zheng Zou, Benyuan Fu, Jinghua Ma, Junjiang Liu and Qi Zhang

Machines 2025, 13(11), 1000; https://doi.org/10.3390/machines13111000 (registering DOI) - 31 Oct 2025

Abstract

As a fundamental element in industrial fluid transportation, the main pump fulfills an irreplaceable function in critical infrastructure, including the energy, water conservancy, petrochemical, and sewage treatment industries. As the core component of key power equipment, its operating condition is intrinsically connected to [...] Read more.

As a fundamental element in industrial fluid transportation, the main pump fulfills an irreplaceable function in critical infrastructure, including the energy, water conservancy, petrochemical, and sewage treatment industries. As the core component of key power equipment, its operating condition is intrinsically connected to the safety, stability, and reliability of the entire system. This paper provides a systematic review of the latest advances in fault mechanism analysis and diagnosis methods for main pump systems. First, the typical structural composition and functional characteristics of the main pump system are examined, and the occurrence mechanisms and evolution rules of typical faults, such as mechanical malfunctions and performance degradation caused by hydraulic imbalance, are discussed in detail. Second, the main technical approaches to fault diagnosis are summarized and reviewed, including diagnosis methods based on signal processing, modeling, data-driven techniques, and multi-source information fusion. The advantages, limitations, and application scopes of these approaches are comparatively analyzed. On this basis, the development trends in main pump fault diagnosis technology and the key challenges faced—such as strong noise, small sample size, and multiple fault coupling—are identified and discussed. Finally, future research prospects are put forward in view of the limitations of current research. This review aims to provide theoretical insights and technical support for advancing condition monitoring, fault diagnosis, and health management of main pump systems. Full article

(This article belongs to the Section Machines Testing and Maintenance)

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22 pages, 9740 KB

Open AccessArticle

Design and Performance Analysis of a High-Temperature Forging Deformation Simulation Device for Dual Manipulators

by Xiaonan Wang, Fugang Zhai, Ziyuan Wang, Zhuofan Yang, Runyuan Zhao and Zunzheng Gu

Machines 2025, 13(11), 999; https://doi.org/10.3390/machines13110999 - 30 Oct 2025

Abstract

To address the difficulty of directly detecting internal stresses in high-temperature forgings during dual-manipulator control experiments and the significant safety risks associated with high-temperature environments, this study developed an experimental device to simulate the deformation behavior of such forgings. First, numerical simulations of [...] Read more.

To address the difficulty of directly detecting internal stresses in high-temperature forgings during dual-manipulator control experiments and the significant safety risks associated with high-temperature environments, this study developed an experimental device to simulate the deformation behavior of such forgings. First, numerical simulations of the elongation process were conducted using DEFORM V11 software to examine the deformation mechanisms of high-temperature forgings. Quantitative results for axial deformation, maximum deformation velocity, and deformation force ranges were obtained, which defined the operational specifications and functional requirements of the device. Second, the mechanical structure and hydraulic system were designed based on engineering principles. The dynamic response characteristics of the simulation device under conventional PID and fuzzy PID control were compared through simulations, and the feasibility of the fuzzy PID control strategy was experimentally verified. Finally, a joint simulation model of the high-temperature forging deformation simulation device and the dual forging manipulator clamping system was established. This model was used to analyze the dynamic response of the simulated workpiece under typical cooperative conditions of dual manipulators and to assess the accuracy of the simulation process during clamping. The results confirmed the practical applicability of the device. Overall, the developed simulation device can effectively reproduce the deformation behavior of high-temperature forgings under ambient conditions, providing a safe and reliable platform for studying coordinated control strategies of dual forging manipulators. Full article

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21 pages, 5218 KB

Open AccessArticle

Biomimetic Nonlinear X-Shaped Vibration Isolation System for Jacket Offshore Platforms

by Zhenghan Zhu and Yangmin Li

Machines 2025, 13(11), 998; https://doi.org/10.3390/machines13110998 - 30 Oct 2025

Abstract

Vibrations induced by marine environmental loads can compromise the operational performance of offshore platforms and, in severe cases, result in structural instability or overturning. This study proposes a biomimetic nonlinear X-shaped vibration isolation system (NXVIS) to suppress earthquake-induced vibration response in offshore platforms. [...] Read more.

Vibrations induced by marine environmental loads can compromise the operational performance of offshore platforms and, in severe cases, result in structural instability or overturning. This study proposes a biomimetic nonlinear X-shaped vibration isolation system (NXVIS) to suppress earthquake-induced vibration response in offshore platforms. Compared with traditional passive vibration isolators, the key innovations of the NXVIS include: (1) the proposed NXVIS can be tailored to different load requirements and resonant frequencies to accommodate diverse offshore platforms and environmental loads; (2) By adjusting isolator parameters (e.g., link length and spring stiffness, etc.), the anti-vibration system can achieve different types of nonlinear stiffness and a large-stroke quasi-zero stiffness (QZS) range, enabling ultra-low frequency (ULF) vibration control without compromising load capacity. To evaluate the effectiveness of the designed NXVIS for vibration suppression of jacket offshore platforms under seismic loads, numerical analysis was performed on a real offshore platform subjected to seismic loads. The results show that the proposed nonlinear vibration isolation solution significantly reduces the dynamic response of deck displacement and acceleration under seismic loads, demonstrating effective low-frequency vibration control. This proposed NXVIS provides a novel and effective method for manipulating beneficial nonlinearities to achieve improved anti-vibration performance. Full article

(This article belongs to the Special Issue Vibration Isolation and Control in Mechanical Systems)

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16 pages, 2429 KB

Open AccessArticle

Biomimetic Design and Optimization of a Rolling-Gear Knee Exoskeleton for High Kinematic Fidelity and Efficiency

by Hui Li, Ming Li, Yujie Su, Disheng Xie, Raymond Kai-Yu Tong and Hongliu Yu

Machines 2025, 13(11), 997; https://doi.org/10.3390/machines13110997 - 30 Oct 2025

Abstract

Biomimetic knee exoskeletons often struggle to balance accurate replication of joint biomechanics with efficient torque transmission. This study presents a knee exoskeleton featuring a single-stage planetary gear set with three coupled interface gears to reproduce the coupled rolling–sliding motion of the human knee. [...] Read more.

Biomimetic knee exoskeletons often struggle to balance accurate replication of joint biomechanics with efficient torque transmission. This study presents a knee exoskeleton featuring a single-stage planetary gear set with three coupled interface gears to reproduce the coupled rolling–sliding motion of the human knee. By mapping rolling and sliding displacements into distinct gear-driven motions, the design achieves a near-linear relationship approximating the physiological J-shaped instantaneous center of rotation (ICR). Gear parameters were optimized under biomechanical and engineering constraints, producing a compact, manufacturable configuration with ICR deviation ≤ 5 mm (sliding distance). Performance experience demonstrates that the optimized joint reduced sliding misalignment of the contact point by 73.4%, delivered peak output torque in agreement with predictions, and maintained an average efficiency of 95.4% across operating speeds. These findings confirm that the proposed mechanism enhances kinematic fidelity and actuation performance, offering a promising solution for next-generation rehabilitation exoskeletons. Full article

(This article belongs to the Special Issue Advanced Rehabilitation Exoskeleton Robots)

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14 pages, 20276 KB

Open AccessArticle

A Discrete Space Vector Modulation MPC-Based Artificial Neural Network Controller for PMSM Drives

by Jiawei Guo, Takahiro Kawaguchi and Seiji Hashimoto

Machines 2025, 13(11), 996; https://doi.org/10.3390/machines13110996 - 30 Oct 2025

Abstract

In addition to the basic voltage vector modulation technique, virtual vectors can be generated through the discrete space vector modulation (DSVM) technique. Consequently, DSVM-based model predictive control (MPC) can achieve the reduction in current harmonics and torque ripples in permanent magnet synchronous machine [...] Read more.

In addition to the basic voltage vector modulation technique, virtual vectors can be generated through the discrete space vector modulation (DSVM) technique. Consequently, DSVM-based model predictive control (MPC) can achieve the reduction in current harmonics and torque ripples in permanent magnet synchronous machine (PMSM) drives. However, as the number of virtual candidate voltage vectors becomes excessively large, the computational burden increases significantly. This paper proposes an artificial neural network (ANN) control algorithm, in which massive input and output datasets generated by an existing DSVM-MPC algorithm are utilized for ANN offline training. In this way, the ANN can efficiently select the optimal voltage vector without enumerating all candidate voltage vectors, thereby reducing the heavy online computation of the DSVM-MPC controller and significantly reducing the computational burden. Finally, the effectiveness of the proposed ANN controller is validated. Full article

(This article belongs to the Section Electrical Machines and Drives)

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18 pages, 4434 KB

Open AccessArticle

Deadbeat Predictive Current Control with High Accuracy Under a Low Sampling Ratio for Permanent Magnet Synchronous Machines in Flywheel Energy Storage Systems

by Xinjian Jiang, Hao Qin, Zhenghui Zhao, Fuwang Li, Zhiru Li and Zhijian Ling

Machines 2025, 13(11), 995; https://doi.org/10.3390/machines13110995 - 29 Oct 2025

Abstract

The predictive current control for the permanent magnet synchronous machine (PMSM) shows great potential in applications like flywheel energy storage, owing to its fast dynamic response and simple structure. However, under low carrier ratio conditions, conventional deadbeat predictive current control (DPCC) exhibits drawbacks [...] Read more.

The predictive current control for the permanent magnet synchronous machine (PMSM) shows great potential in applications like flywheel energy storage, owing to its fast dynamic response and simple structure. However, under low carrier ratio conditions, conventional deadbeat predictive current control (DPCC) exhibits drawbacks such as significant current prediction error, inaccurate instruction voltage calculation, and severe torque and flux linkage coupling. This paper proposes an improved DPCC method suitable for both high and low carrier ratio operation of the PMSM. First, a modified stator voltage equation is established considering rotor flux orientation error. By treating the dq-coordinates as stationary and accounting for rotor rotation within the control period, a dynamic PMSM model is developed, effectively suppressing cross-axis coupling under low carrier ratios. Simultaneously, a multi-coordinate variable synchronization method is also introduced to eliminate prediction and voltage errors caused by cross-coordinate computation, enabling precise deadbeat control across all carrier ratios. The experimental results demonstrate that the proposed method enhances torque-flux decoupling, improves current prediction and tracking accuracy at low carrier ratios, and offers a reliable solution for dynamic control in flywheel energy storage systems. Full article

(This article belongs to the Section Electrical Machines and Drives)

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18 pages, 2340 KB

Open AccessArticle

The Potential of Using Birotor Machines in Modern Transport Means

by Oleksij Fomin, Mikhaylo Chubykalo, Oleksandr Lohvinenko, Václav Píštěk and Pavel Kučera

Machines 2025, 13(11), 994; https://doi.org/10.3390/machines13110994 - 29 Oct 2025

Abstract

The transport sector requires compact, reliable, and energy-efficient power units for modernization of road, rail, maritime, and aerial systems. Conventional piston and rotary machines often face limitations related to vibration, sealing losses, and manufacturing complexity. This study investigates birotor machines (BM), a class [...] Read more.

The transport sector requires compact, reliable, and energy-efficient power units for modernization of road, rail, maritime, and aerial systems. Conventional piston and rotary machines often face limitations related to vibration, sealing losses, and manufacturing complexity. This study investigates birotor machines (BM), a class of positive-displacement devices combining synchronized rotation of the rotor and housing. This configuration ensures smooth kinematics, near-complete dynamic balance, and simplified design. The working principle enables continuous volumetric transformation with reduced friction and leakage, enhancing efficiency and durability. Using generalized mathematical models (GMM) developed through statistical experimental design, optimal geometric parameters were determined with a root-mean-square error below 3%. A prototype birotor compressor (BC) designed for subway rolling stock achieved equivalent output performance (0.43 m³/min at 0.8 MPa) with 82% efficiency and a mass reduction from 130 kg to 32 kg. Comparative simulations and preliminary testing of BM-based internal combustion engines (BRICE) demonstrated 3–4 times smaller and lighter units with improved reliability and environmental characteristics. The results confirm that BM technology provides a feasible and manufacturable alternative to conventional designs, suitable for integration into next-generation transport and unmanned vehicle systems. Full article

(This article belongs to the Section Machine Design and Theory)

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22 pages, 21876 KB

Open AccessArticle

Dynamic Analysis and Design of Cylindrical Roller Bearings with Arc End Surfaces of Rollers

by Maokuan Bao, Liqin Wang and Chuanwei Zhang

Machines 2025, 13(11), 993; https://doi.org/10.3390/machines13110993 - 29 Oct 2025

Abstract

The new contact model for arc end surfaces of rollers and flanges is established in a dynamic model for cylindrical roller bearings. The dynamic behaviors between roller arc end surfaces and flanges, i.e., contact pressures, sliding velocities, and PV values (peak contact pressure [...] Read more.

The new contact model for arc end surfaces of rollers and flanges is established in a dynamic model for cylindrical roller bearings. The dynamic behaviors between roller arc end surfaces and flanges, i.e., contact pressures, sliding velocities, and PV values (peak contact pressure P × sliding velocity V), are investigated and compared to those between roller corners and flanges. Based on the indicators of contact heights and axial clearances, the selection ranges of layback angles, flange axial clearances, and end radius of rollers are proposed, thereby ensuring the bearing operates normally. The results indicate that arc end surfaces are beneficial in reducing contact pressures, sliding velocities, and PV values acting on flanges, especially under high-speed conditions. With less layback angles of flanges and end radii of rollers, contact positions on rollers are more concentrated and the sliding velocity decreases obviously. However, flange heights need to be increased to prevent contact heights between rollers and flanges within the limited zones. Furthermore, since the end radius of rollers leads to a decrease in the axial clearance of flanges, the actual clearance of flanges under axial direction needs to be widened. Full article

(This article belongs to the Special Issue Tribology in Bearing Design for High-Speed and Energy-Efficient Mechanical Systems)

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26 pages, 5541 KB

Open AccessArticle

Intelligent Recognition of Weld Seams on Heat Exchanger Plates and Generation of Welding Trajectories

by Fuyao Xie, Mingda Huang, Neng Wang, Linyuxuan Li and Xianhai Yang

Machines 2025, 13(11), 992; https://doi.org/10.3390/machines13110992 - 29 Oct 2025

Abstract

The large-format, long-distance welding of heat exchanger plates is widely used in shipbuilding, oil and gas, power and metallurgical equipment, rail transportation, and other fields. To address issues such as low automation and information silos in actual welding production, this paper proposes an [...] Read more.

The large-format, long-distance welding of heat exchanger plates is widely used in shipbuilding, oil and gas, power and metallurgical equipment, rail transportation, and other fields. To address issues such as low automation and information silos in actual welding production, this paper proposes an intelligent weld seam identification and trajectory generation method, accurately achieving coordinate generation for large-format, long-distance heat exchanger plate welding. The method investigates a camera calibration model based on coordinate transformation, preprocesses collected weld seam images, develops an edge approximation algorithm using median filters for denoising, and proposes a two-stage fusion strategy of “deep learning localization + optimized operator refinement” for edge intelligent identification. This strategy utilizes deep learning object detection for the fast and robust coarse localization of weld regions, combined with optimized operators for high-precision, efficient pixel-level edge extraction. Finally, a weld trajectory coordinate generation program based on the Hough transform algorithm is developed, enabling the rapid automatic welding of plates by welding robots. Experiments demonstrate the accurate identification of heat exchanger plate welds with an error of only 0.33%, meeting welding requirements. The method shows the fast integration of identification and welding information: overall welding efficiency improved by over 100%, and we achieved strong real-time performance, compatibility, and low hardware requirements. Full article

(This article belongs to the Section Advanced Manufacturing)

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19 pages, 6117 KB

Open AccessArticle

Impact of Crown-Type Cage Eccentricity in New Energy Vehicle Motor Ball Bearings on Their Dynamic Performance

by Haisheng Yang, Jiahang Zhang, Run Zhang, Zhanwang Shi and Haiyang Dong

Machines 2025, 13(11), 991; https://doi.org/10.3390/machines13110991 - 29 Oct 2025

Abstract

In response to the increasing demands for cage strength and operational stability of ball bearings in new energy vehicle motors operating under high-speed and light-load conditions, this paper focuses on the 6207 deep groove ball bearing as the research subject. It systematically analyzes [...] Read more.

In response to the increasing demands for cage strength and operational stability of ball bearings in new energy vehicle motors operating under high-speed and light-load conditions, this paper focuses on the 6207 deep groove ball bearing as the research subject. It systematically analyzes the influence of various structural parameters of the crown-type cage, including profile radius, side beam thickness, claw length, and claw radius, on its eccentricity. Furthermore, the paper explores the mechanism by which eccentricity affects the dynamic performance of the cage. By establishing a rigid–flexible coupled dynamics model and conducting simulation analyses, the results indicate that the claw ends of the crown-type cage pockets are the regions of maximum deformation, while the pocket bottom experiences the highest equivalent stress, identifying it as a critical location for fracture failure. The research demonstrates that the impact of eccentricity on performance is non-monotonic: a reduction in eccentricity can significantly diminish the collision force between the balls and the cage, decrease vibration amplitude, and lower equivalent stress; concurrently, the maximum cage deformation and vibration acceleration level increase correspondingly. Additionally, the centrifugal force acting on the cage itself significantly elevates the equivalent stress. Therefore, the optimal design of the crown-type cage necessitates a comprehensive trade-off among multiple objectives, including strength and stability. It is essential to avoid inappropriate eccentricity design that may arise from the pursuit of a single performance indicator (such as friction reduction or weight reduction), thereby providing a theoretical foundation for the refined design of high-performance bearing cages. Full article

(This article belongs to the Section Vehicle Engineering)

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44 pages, 4366 KB

Open AccessReview

Design Methods and Practices for Centrifugal Compressor Diffusers: A Review

by Oana Dumitrescu, Sergiu Strătilă and Valeriu Drăgan

Machines 2025, 13(11), 990; https://doi.org/10.3390/machines13110990 - 28 Oct 2025

Abstract

The design of diffusers is a critical aspect of compressor performance, directly influencing pressure recovery, flow stability, and overall stage efficiency and operating range. This review paper provides an analysis of diffuser design principles, methodologies, and practical considerations in turbomachinery applications. The importance [...] Read more.

The design of diffusers is a critical aspect of compressor performance, directly influencing pressure recovery, flow stability, and overall stage efficiency and operating range. This review paper provides an analysis of diffuser design principles, methodologies, and practical considerations in turbomachinery applications. The importance of diffusers in compressors is discussed, and the main types of diffusers are presented, highlighting, for each type of diffuser, their aerodynamic characteristics and operational advantages. Traditional empirical correlations and analytical models for diffuser geometry generation are reviewed, emphasizing their role in guiding preliminary design decisions. The integration of one-dimensional (1D) performance analysis methods with computational fluid dynamics (CFD) simulations is also discussed, illustrating how these approaches improve performance prediction and optimization accuracy. Design constraints are analyzed alongside performance trade-offs, highlighting the need to balance efficiency and stability. Overall, this review synthesizes existing knowledge on diffuser design in compressors, providing a structured framework for engineers and researchers to understand the key factors affecting performance and guiding the development of efficient, reliable diffuser configurations for real-world turbomachinery applications. Full article

(This article belongs to the Section Turbomachinery)

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22 pages, 4691 KB

Open AccessReview

Comprehensive Survey of Micro Turbojet Experimentation: Sensor Technologies, Methodologies, and Research Trends

by Ahmed M. Shehata and Marco P. Schoen

Machines 2025, 13(11), 989; https://doi.org/10.3390/machines13110989 - 28 Oct 2025

Abstract

From advanced research platforms to Unmanned Aerial Vehicles (UAVs), Micro Turbojet Engines (MTEs) have grown to be essential parts in many different kinds of applications. Extensive testing, encompassing analysis, alternative fuel suitability, performance characterization, and control system validation, supports their development. This survey [...] Read more.

From advanced research platforms to Unmanned Aerial Vehicles (UAVs), Micro Turbojet Engines (MTEs) have grown to be essential parts in many different kinds of applications. Extensive testing, encompassing analysis, alternative fuel suitability, performance characterization, and control system validation, supports their development. This survey examines the current state of MTE experimentation, along with information on experimental methods, sensor technologies, and new directions in corresponding research. Measurement techniques, alternative fuel effects, characterization of gaseous and particle emissions, and the utilization of experimental data to validate control systems and sophisticated engine models are among the recent advances in test bed design discussed here. Presenting an overall view, the aim is to highlight current challenges and inspire more MTE technology advancement. Full article

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27 pages, 3199 KB

Open AccessArticle

Heat Loss Calculation of the Electric Drives

by Tamás Sándor, István Bendiák, Döníz Borsos and Róbert Szabolcsi

Machines 2025, 13(11), 988; https://doi.org/10.3390/machines13110988 - 28 Oct 2025

Abstract

In the realm of sustainable public transportation, the integration of intelligent electric bus propulsion systems represents a novel and promising approach to reducing environmental impact—particularly through the mitigation of NOx emissions and overall exhaust pollutants. This emerging technology underscores the growing need for [...] Read more.

In the realm of sustainable public transportation, the integration of intelligent electric bus propulsion systems represents a novel and promising approach to reducing environmental impact—particularly through the mitigation of NOx emissions and overall exhaust pollutants. This emerging technology underscores the growing need for advanced drive control architectures that ensure not only operational safety and reliability but also compliance with increasingly stringent emissions standards. The present article introduces an innovative analysis of energy-optimized dual-drive electric propulsion systems, with a specific focus on their potential for real-world application in emission-conscious urban mobility. A detailed dynamic model of a dual-drive electric bus was developed in MATLAB Simulink, incorporating a Fuzzy Logic-based decision-making algorithm embedded within the Transmission Control Unit (TCU). The proposed control architecture includes a torque-limiting safety strategy designed to prevent motor overspeed conditions, thereby enhancing both efficiency and mechanical integrity. Furthermore, the system architecture enables supervisory override of the Fuzzy Inference System (FIS) during critical scenarios, such as gear-shifting transitions, allowing adaptive control refinement. The study addresses the unique control and coordination challenges inherent in dual-drive systems, particularly in relation to optimizing gear selection for reduced energy consumption and emissions. Key areas of investigation include maximizing efficiency along the motor torque–speed characteristic, maintaining vehicular dynamic stability, and minimizing thermally induced performance degradation. The thermal modeling approach is grounded in integral formulations capturing major loss contributors including copper, iron, and mechanical losses while also evaluating convective heat transfer mechanisms to improve cooling effectiveness. These insights confirm that advanced thermal management is not only vital for performance optimization but also plays a central role in supporting long-term strategies for emission reduction and clean, efficient public transportation. Full article

(This article belongs to the Section Electrical Machines and Drives)

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17 pages, 1985 KB

Open AccessArticle

Parameter Identification in FEM of Mechanical Structure Within NPP Based on Seismic Response

by Genfei Li, Peiyue Li, Pengju Zhao, Ruiyuan Xue, Linbin Li and Pengcheng Geng

Machines 2025, 13(11), 987; https://doi.org/10.3390/machines13110987 - 28 Oct 2025

Abstract

Reliable finite element models (FEMs) are required in seismic qualification of mechanical structures within a nuclear power plant (NPP). The relative displacement response of such mechanical structures is difficult to measure, and it is costly to extract enough modes. Therefore, the modification of [...] Read more.

Reliable finite element models (FEMs) are required in seismic qualification of mechanical structures within a nuclear power plant (NPP). The relative displacement response of such mechanical structures is difficult to measure, and it is costly to extract enough modes. Therefore, the modification of the initial FEM by the common FEM updating method could not always be carried out smoothly. In this paper, a vibration control equation error-based two-stage FEM updating method is proposed to identify uncertain parameters in the FEMs, which is capable of employing seismic response in the form of acceleration. Optimal values of updating parameters are searched by using the Marquardt method, which is effective in avoiding the ill-conditioned iterative equation. Numerical simulation is performed for the steam pipeline to validate the actual feasibility and robustness of the proposed method. The fact that the distribution of damping is independent of the identification of parameters related to the mass and stiffness matrices is also demonstrated. Finally, experimental validation of the method is carried out on a load-bearing pipeline. The damping coefficients of the pipeline are modified independently by back propagation neural network. Full article

(This article belongs to the Section Machines Testing and Maintenance)

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25 pages, 5952 KB

Open AccessArticle

Research on Vibration-Damping and Deflection Correction of BTA Deep Hole Drilling Tool Systems Based on Dynamic Pressure Lubrication and Squeeze Film Theory

by Yu Wang, Tong Chen and Daguo Yu

Machines 2025, 13(11), 986; https://doi.org/10.3390/machines13110986 - 27 Oct 2025

Abstract

In the processes of deep hole drilling and boring, tool deflection and chatter are prevalent problems that significantly affect the quality and efficiency of deep hole part machining. This paper designs a Helical-Type Vibration-Damping and Deflection Correction Device for BTA (boring and trepanning [...] Read more.

In the processes of deep hole drilling and boring, tool deflection and chatter are prevalent problems that significantly affect the quality and efficiency of deep hole part machining. This paper designs a Helical-Type Vibration-Damping and Deflection Correction Device for BTA (boring and trepanning association) deep hole drilling based on the principles of fluid dynamic pressure lubrication and squeeze film damping. By leveraging the flow field characteristics of cutting oil during machining, the device achieves vibration-damping, deflection correction, and enhanced support for the tool system throughout the drilling operation. Through theoretical analysis, this research examines the oil film pressure distribution and stability of the Designed Vibration-Damping and Deviation Correction Device. It also explores the influence patterns of factors such as cutting parameters, device structure, minimum film thickness, film thickness ratio, and length-to-diameter ratio on its vibration-damping, deviation correction, and stability performance. Taking a

ϕ 29.35

deep hole as the research object, an experimental platform was designed and constructed to measure and verify the device’s vibration-damping and deviation correction effects under different operating conditions. Deep hole drilling tests were carried out on 10 conventional gun steel specimens (

ϕ 29.35

× 3000

m m

). The results indicate that, when the minimum oil film gap of the Vibration-Damping and Deflection Correction Device is 0.08

m m

, the axis deviation range is 0.27~0.45

m m

, with a surface roughness of 0.589 to 0.677

μ m

. Compared to similar conditions without the device, these represent reductions of 55~73% and 47.07~53.95%, respectively. It allows for a reduction of over 10% in blank material allowance and an increase of 5–15% in tool feed rates. Full article

(This article belongs to the Special Issue Design and Manufacturing for Lightweight Components and Structures)

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13 pages, 1751 KB

Open AccessArticle

Influence of Carbon Fiber Reinforcement on Mechanical and Thermal Behavior of PLA and PAHT in Additive Manufacturing

by Mamoun Alshihabi, Mahdi El Said, Abdussalam Alshami, Shafahat Ali and Ibrahim Deiab

Machines 2025, 13(11), 985; https://doi.org/10.3390/machines13110985 - 25 Oct 2025

Abstract

This study explores the comparative evaluation of PLA, carbon fiber-reinforced PLA (PLA-CF), and carbon fiber-reinforced high-temperature polyamide (PAHT-CF) for use in Fused Deposition Modeling (FDM) additive manufacturing. These materials were selected to examine how carbon fiber (CF) reinforcement affects PLA and PAHT, using [...] Read more.

This study explores the comparative evaluation of PLA, carbon fiber-reinforced PLA (PLA-CF), and carbon fiber-reinforced high-temperature polyamide (PAHT-CF) for use in Fused Deposition Modeling (FDM) additive manufacturing. These materials were selected to examine how carbon fiber (CF) reinforcement affects PLA and PAHT, using virgin PLA as the baseline. Mechanical and thermal properties were tested to assess the influence of reinforcement on strength, toughness, and heat transfer. Tensile, impact, and thermal conductivity tests were conducted on all three materials. The results showed that PAHT-CF outperformed both PLA and PLA-CF in all categories, achieving an ultimate tensile strength of 57.5 MPa, an impact strength of 14.30 kJ/m², and thermal conductivity of 0.182 W/m·K. PLA-CF showed moderate improvements in strength over neat PLA but with increased brittleness and slight improvement in thermal conductivity. Notably, this is the first study to investigate the thermal conductivity and resistivity of PAHT-CF in the literature, offering new insights into its heat dissipation capabilities and suitability for high-temperature applications. These findings highlight the critical role of polymer selection and fiber reinforcement in optimizing material performance. The results offer guidance for material selection in additive manufacturing, especially for lightweight, strong, and thermally efficient parts in various industries. Full article

(This article belongs to the Special Issue Innovations and Challenges in Additive Manufacturing Technologies)

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