Search Results (784)

In this study, a novel direct torque control (DTC) strategy is proposed to mitigate the torque ripple issue inherent in switched reluctance motors (SRMs), which is caused by the double salient pole configuration and the pulse power supply mode. The strategy is based on the prediction and optimization of a long-time-domain model. Central to this method is the development of a multi-step predictive optimization framework. By incorporating hysteresis control, the conventional approach of minimizing instantaneous error in predictive control is shifted towards minimizing tracking error over an extended time frame. A dual-objective evaluation function is also introduced, which simultaneously optimizes both torque smoothness and switching frequency, ensuring their collaborative enhancement. To validate the proposed method, a 6/4-pole SRM simulation model was implemented using MATLAB/Simulink 2024B, and comparisons were made with traditional methods. The results demonstrate that this strategy significantly reduces torque pulsation and lowers the system’s switching frequency, even under varying operational conditions such as different rotational speeds and sudden load variations. Consequently, this approach not only guarantees improved dynamic performance but also enhances the motor’s efficiency and stability. Full article

Axial Flux Permanent Magnet Synchronous Motors (AFPMSMs) are gaining increasing attention for their application in electric vehicle (EV) drive systems. Their high torque density and compact axial geometry make them attractive for high-performance EV drive systems. However, cogging torque remains a major challenge, degrading low-speed drivability, noise performance, and control stability. This article proposes a magnet skew on rotor modulation structure using a genetic algorithm (GA) to reduce cogging torque in AFPMSMs utilizing a 12/15 non-integer pole/slot arrangement. The objective of optimization is to simultaneously reduce cogging torque under identical electromagnetic constraints. A complete three-dimensional finite element model (3D-FEM) incorporating nonlinear magnetic material properties has been developed to evaluate the electromagnetic field distribution and torque components. The results indicate that a 12/15 non-integer pole/slot arrangement improves harmonic distribution and extends the operating range with lower cogging torque compared to integer pole/slot designs. Combined with GA-optimized skew angles, this reduces peak-to-peak cogging torque to less than 50%. This design is ideally suited for the traction requirements of electric vehicles, including premium electric vehicles where smooth operation at low speeds is critical. Full article

Background: We assessed the effects of a 6-week, low-volume Nordic hamstring exercise (NHE) intervention on hamstring flexibility, muscle mechanical properties and eccentric and isometric isokinetic knee flexion strength in recreationally active adults. Methods: Eighteen recreationally active adults were randomized into an NHE intervention group (IG; n = 9; females/males: 3/6; mean ± SD, age: 24.1 ± 1.3 years) and control group (CG; n = 9; females/males: 5/4; mean ± SD, age: 23.5 ± 1.8 years). The NHE intervention involved a progressive, supplementary training program performed initially one (weeks 1 and 2) and then two times per week over a 6-week period. The number of repetitions per session increased from 15 to 36 repetitions/week. The CG maintained their usual exercise routine over the same period. Standard goniometry, myotonometry, and isokinetic dynamometry (60°/s) were used to measure hamstring flexibility, muscle properties and isometric and eccentric isokinetic strength prior to and five days following the intervention. Results: The Linear Mixed Methods analysis identified a significant group × time interactions for isometric torque (IG: +5% vs. CG: −12%, p = 0.022) and flexibility (IG: +1% vs. CG: +7%, p = 0.023). Peak eccentric torque (IG: +7% vs. CG: −7%, p = 0.053) and muscle mechanical properties remained unchanged over the intervention period. Conclusions: Six weeks of low-volume NHE training marginally improved isometric and eccentric hamstring strength in recreationally active adults without changing hamstring flexibility or mechanical properties. The findings may have important implications for performance enhancement and hamstring injury risk reduction during high-intensity recreational sports. Full article

This study presents a stator-focused electromagnetic optimization of a 350 W, 27-slot, 30-pole outer-rotor brushless direct current (BLDC) motor developed for electric scooter applications. Unlike conventional redesign approaches that modify rotor topology or overall motor dimensions, the proposed methodology preserves the rotor structure and external geometry of a commercially validated reference motor and improves performance primarily through targeted stator geometric refinement, with minor adjustments in the winding configuration. A two-stage optimization strategy combining parametric analysis and genetic algorithm (GA)-based multi-objective optimization is implemented to minimize cogging torque and torque ripple while maximizing efficiency. Finite element analyses (FEA) were conducted to evaluate back electromotive force (back-EMF) characteristics, magnetic flux density distribution, torque behavior, and current density. Experimental validation confirms a 54.86% reduction in cogging torque (from 257 mNm to 116 mNm), a 19.6% decrease in torque ripple, a 6.17% reduction in maximum current density, and a 2–3% improvement in efficiency within the nominal load range (5.2–6.45 Nm), reaching 85.69% efficiency at 350 W output power. The results demonstrate that systematic stator geometry optimization, supported by minor winding modifications, can significantly enhance efficiency, torque smoothness, and thermal margin without increasing motor size, rated power, or manufacturing complexity. This work provides a practical and manufacturable design pathway for high-performance outer rotor BLDC motors in light electric vehicle (LEV) propulsion systems. Full article

This study proposes a vibration reduction strategy for a 12-slot, two-pole permanent magnet brushed DC (PMDC) motor used in automotive blower systems. A multi-parameter optimization framework combining finite element analysis and experimental validation is developed to address cogging torque, a critical source of electromagnetic vibration and acoustic noise. The influence of pole arc coefficient and permanent magnet eccentricity on cogging torque is systematically investigated using response surface methodology, identifying an optimal design with significantly reduced torque ripple and vibration. Furthermore, a machine learning model based on the random forest algorithm is introduced to predict cogging torque, air gap magnetic flux density, and output torque, achieving high accuracy and strong generalizability. The results confirm that the optimized motor structure suppresses resonance-induced noise near 7500 Hz, improving overall motor stability and acoustic performance. The proposed data-driven design approach offers a reliable and efficient pathway for vibration optimization in low-cost automotive PMDC motors. Full article

Objectives/Background: Aerobic exercise serves as a fundamental component in improving metabolic health. However, because obese middle-aged women often find it difficult to maintain long-term exercise participation, more efficient alternative strategies, such as whole-body electromyostimulation (WB-EMS), need to be explored. This study investigated the effects of aerobic exercise combined with WB-EMS on muscle and pulmonary functioning and metabolic health indicators in obese middle-aged women in South Korea, where obesity rates have been steadily increasing. Methods: Women aged 40–65 years with a body mass index ≥25 kg/m² who met at least three diagnostic criteria for metabolic syndrome were recruited. Of the 45 recruits, 36 completed the study. Participants were randomly assigned to a control (CON), aerobic exercise (EXG), or aerobic exercise with WB-EMS (WEG) group. The intervention consisted of a 12-week aerobic program performed three times per week for 40 min per session, with WB-EMS applied during the main exercise period. Muscle function, pulmonary function, and metabolic health indicators were assessed. Data were analyzed using two-way repeated-measures analysis of variance. Statistical significance was set at p < 0.05. Results: Significant group × time interaction effects were observed for muscle strength outcomes, with knee extensor and flexor peak torque at 60°/s (p < 0.001 for the right and left knee extensors; p = 0.001 for right knee flexors; p < 0.001 for left knee flexors). Post hoc comparisons indicated greater improvements in the WEG than in both the CON and EXG. Forced vital capacity (FVC) showed significant group × time interactions and time main effects (both p < 0.001), whereas forced expiratory volume in one second (FEV₁) and the FEV₁/FVC ratio showed no significant group, time, or interaction effects (all p > 0.05). Regarding metabolic health, BMI and waist-to-hip ratio showed significant time effects, indicating overall reductions following the intervention without significant interaction effects. Low-density lipoprotein cholesterol (p = 0.004) and fasting plasma glucose (p = 0.004) showed significant group × time interaction effects; however, post hoc analyses revealed no significant differences between the WEG and EXG. No consistent additional metabolic benefits of WB-EMS beyond aerobic exercise alone were observed. Conclusions: The 12-week aerobic exercise program improved muscle strength, pulmonary function, and selected metabolic indicators in obese middle-aged women. Aerobic exercise combined with WB-EMS provided additional benefits primarily for muscle strength compared with aerobic exercise alone, without conferring additional metabolic advantages. Full article

The rapid electrification of road vehicles has fundamentally reshaped the priorities of noise, vibration, and harshness (NVH) engineering. In the absence of combustion-related broadband masking, tonal and order-related phenomena originating from the electric machine, inverter switching, and high-speed reduction gearing have become clearly perceptible and, in many cases, acoustically dominant. Consequently, drivetrain noise in electric vehicles can no longer be assessed at component level alone; it must be understood as a coupled system response shaped by excitation mechanisms, structural dynamics, transfer paths, radiation efficiency, and ultimately human perception. This review adopts a source-to-perception perspective and consolidates the principal physical mechanisms governing vibro-acoustic behavior in integrated electric drive units. Electromagnetic force harmonics and torque ripple are discussed alongside transmission-error-driven gear mesh excitation, while bearing and shaft nonlinearities are examined in the context of high-speed operation. In addition, ancillary thermoacoustic and aerodynamic contributions are considered, reflecting the increasingly integrated packaging of modern e-axle architectures. On this mechanism-oriented basis, dominant excitation types are linked to frequency-appropriate modeling strategies, spanning electromagnetic force extraction, multibody drivetrain simulation, structural finite element analysis, transfer path analysis, and acoustic radiation prediction. Particular attention is given to workflow integration across domains. Finally, the paper identifies research challenges that predominantly arise at system level, including multi-source interaction effects, installation-dependent transfer-path variability, emergent resonances in assembled structures, manufacturing-induced tonal artifacts, and the still limited correlation between predicted vibration fields and perceived sound quality. Full article

Digital twin (DT) technologies are increasingly applied in manufacturing to support monitoring, optimization, and predictive maintenance; however, most implementations remain operationally focused and disconnected from system-level decision-making and lifecycle engineering. This limitation is particularly critical in manufacturing environments that exhibit System-of-Systems (SoS) characteristics, where performance emerges from the interactions among autonomous, interdependent subsystems. This study proposes an integrated systems engineering framework in which the digital twin functions as a system-level integrator rather than a standalone simulation tool. The framework embeds Quality Function Deployment (QFD), Analytic Hierarchy Process (AHP), Reliability and Safety analysis (RAMST), and Statistical Process Control (SPC) within a unified digital twin architecture, enabling explicit traceability from stakeholder requirements to design decisions, operational control, and lifecycle performance. The framework is demonstrated through a robotic fastening system operating under high variability, multi-vendor integration, and reliability constraints. A high-fidelity digital twin was developed in MATLAB Simscape and synchronized with operational data via virtual sensors and SPC-based monitoring. Results from a 35-month simulation study (n = 1050 operations) show a 30% reduction in system downtime and a 15% improvement in fastening quality (torque and angle compliance), supported by 95% confidence intervals, alongside enhanced fault detection and preventive maintenance capabilities. The findings demonstrate that integrating decision-making, monitoring, and learning within a single DT environment supports resilient, adaptive manufacturing systems aligned with Industry 4.0–5.0 objectives. Full article

This study investigates the incorporation of toner residue (TR), derived from post-consumer printing cartridges, as an alternative filler in styrene–butadiene rubber (SBR) composites, with emphasis placed on solid waste valorization and the promotion of a circular economy. TR consists predominantly of fine particles containing thermoplastic polymers, carbon black, metal oxides, and additives, exhibiting functional potential as a partially reinforcing filler material. Composites containing 0 to 50 phr of TR were prepared and characterized in terms of rheometric properties, dispersion degree, elemental composition by X-ray fluorescence (XRF), crosslink density, scanning electron microscopy (SEM), infrared spectroscopy, Shore A hardness, abrasion resistance, tensile strength, and tear resistance. Rheometric results indicated modifications in vulcanization kinetics and a reduction in maximum torque for formulations with high TR contents, suggesting a possible diluent effect or interference with elastomeric network formation. Conversely, moderate TR concentrations promoted increased hardness, improved tensile strength, and higher crosslink density, associated with adequate particle dispersion within the matrix, as confirmed by SEM analysis. However, excessive TR loading led to increased abrasion loss and an overall reduction in mechanical performance. It is concluded that TR demonstrates technical feasibility as a partial substitute for conventional fillers in SBR composites, with potential industrial application, such as in footwear sole prototypes, combining functional performance with environmental impact mitigation. Full article

This study presents a comprehensive comparative analysis of the performance, combustion, and emission characteristics of a single-cylinder, four-stroke spark-ignition engine fueled by commercial gasoline and raw biogas enhanced with cerium oxide (CeO₂) nanoparticles. Raw biogas containing 58% methane was tested without carbon dioxide removal to reflect practical rural applications, while CeO₂ nanoparticles were ultrasonically dispersed in the fuel to promote homogeneous suspension and catalytic activity. Experiments were conducted under wide-open and part-throttle conditions across a range of engine speeds, with simultaneous measurement of brake thermal efficiency, brake-specific fuel consumption, volumetric efficiency, in-cylinder pressure, heat release rate, combustion phasing, and regulated emissions. The results showed that while gasoline consistently outperformed biogas in torque and power due to its higher heating value and flame speed, the addition of CeO₂ significantly reduced the performance gap. For the biogas mode, CeO₂ addition increased brake thermal efficiency by up to 5%, lowered brake-specific fuel consumption by up to 8%, and shifted the start of main combustion to earlier crank angles, indicating faster and more complete combustion, particularly at high loads where higher temperatures activate CeO₂’s catalytic behavior. Emission analysis revealed that CeO₂-blended biogas reduced carbon monoxide emissions by approximately 25% and unburned hydrocarbons by up to 55% compared with gasoline, while nitrogen oxide emissions were consistently 15–22% lower. These reductions were observed across both wide-open and part-throttle conditions, confirming improved combustion completeness and lower peak flame temperatures. These improvements are attributed to CeO₂’s oxygen-storage capability, catalytic oxidation activity, and enhanced thermal conductivity, which collectively strengthen combustion completeness and cyclic stability. The findings demonstrate that nanoparticle-enhanced biogas can substantially improve the environmental and operational viability of spark-ignition engines, offering a practical pathway for integrating renewable gaseous fuels into existing transportation systems. Full article

The implementation of methanol-ammonia dual-fuel engines has the potential to contribute to a reduction in carbon emissions in the environment. The present study employs numerical simulations of the methanol-ammonia dual-fuel engine to investigate methanol direct injection pre-injection strategies. The impact of pre-main injection time interval and pre-injection quantity was investigated on output power, output torque, cylinder pressure and exhaust emissions such as NO_X, HC, CO, and CO₂. The results show that compared with the single methanol injection strategy, increasing the pre-injection strategy can effectively reduce soot emissions. Under certain pre-injection conditions, NO_X and soot emissions can also be significantly reduced. Compared with low pre-injection quantities, by using high pre-injection quantities, soot and NO_X emissions can be reduced by 36.91% and 35.31%, respectively. Under high pre-injection quantities, increasing the pre-main injection time interval can also significantly reduce NO_X emissions. Compared with the single methanol injection strategy, the pre-injection strategy leads to an increase in cylinder pressure peak and an advance in peak timing. As the pre-main injection time interval increases, both output power and output torque decrease. It is found that when the pre-injection quantity is 6 mg and the pre-main injection time interval is 25 °CA, with no substantial reduction in output power and output torque, the engine’s soot emissions can be reduced by 34.67%, and NO_X emissions can be reduced by 30.31%. Full article

This paper presents an efficient stand-alone photovoltaic water pumping system (PVWPS) intended for agricultural irrigation applications, operating without energy storage. The system employs a three-phase induction motor supplied by a three-level neutral point clamped (NPC) inverter. The proposed control strategy integrates the advantages of two distinct controllers to enhance both energy extraction and drive performance. On the photovoltaic side, a fuzzy logic-based maximum power point tracking (MPPT) algorithm is implemented to ensure continuous operation at the global maximum power point under rapidly varying irradiance conditions. On the motor drive side, a direct torque control (DTC) scheme is combined with the multilevel NPC inverter to regulate electromagnetic torque and stator flux. The use of a multilevel inverter significantly mitigates the inherent drawbacks of conventional DTC, notably torque and flux ripples, as well as stator current harmonic distortion. The overall control architecture maximizes power transfer from the photovoltaic generator to the pumping system, resulting in improved dynamic response and energy efficiency. The proposed system is validated through detailed MATLAB/Simulink simulations under abrupt irradiance variations and a realistic daily solar profile corresponding to August conditions in Kairouan, Tunisia. Simulation results demonstrate substantial performance improvements, including an 88% reduction in torque ripples, a 50% decrease in flux ripple, a 77.9% reduction in stator current THD, and a 33.3% enhancement in speed transient response compared to conventional DTC-based systems. Full article

Permanent magnet synchronous motors (PMSMs) are utilized in demanding conditions and applications requiring precision and accuracy, such as servo systems. Especially at low speeds, the effects of cogging torque, current measurement and offset errors, improper controller gains, mechanical resonance, and torque fluctuations caused by load torque and flux result in fluctuations at various frequencies in the motor output speed. This study, motivated by two factors, proposes an extended state observer (ESO)-based multivariable fast response extremum-seeking (FESC) interval type-2 fuzzy PID (IT2FPID) controller to improve dynamic response and reduce speed ripple at low speeds in situations where all these negative factors could arise. This approach enables the real-time adaptation of parameters to counteract the decline in controller performance caused by the nonlinear characteristics of PMSMs and parameter fluctuations while also optimizing disturbance rejection in the speed response under varying operating conditions and existing speed ripple. The experimental results from the prototype setup validate that the proposed control mechanism is functional, valid, and precise in diminishing speed ripples during low-speed operations. The simulation and test outcomes of the control scheme show that speed noise at low speeds is reduced from 26% to 3% compared to traditional proportional-integral (PI) controller and supertwisting (STW) sliding mode controller (SMC) responses and that the scheme exhibits a 16–23% reduction in undershoot amplitude and faster recovery in the presence of load torque variations. Full article

This study presents a novel self-adaptive marine current power generation system capable of operating efficiently across a wide range of flow velocities. The key innovations include an adaptive variable-solidity rotor and a non-contact magnetic speed-increasing dynamic seal. The rotor employs foldable blades that enable passive solidity regulation in response to varying inflow conditions. At low flow velocities, the blades remain deployed, increasing rotor solidity and reducing the required startup flow velocity. Water tank experiments indicate that the minimum startup velocity of the variable-solidity rotor is 0.217 m/s, which represents a 38% reduction compared to a conventional rotor. At high flow velocities, the blades fold under increased hydrodynamic loading, thereby reducing the effective solidity and suppressing torque growth to provide overload protection. The power transmission module incorporates a non-contact magnetic speed-increasing dynamic seal, which ensures underwater dynamic sealing of the main shaft while simultaneously increasing the rotational speed of the driven shaft. Motor-driven bench tests demonstrate that when the active shaft speed remains below the cut-off threshold, a stable speed-increasing ratio of 2:1 is maintained, enabling effective speed amplification and torque transmission. Once the active shaft speed exceeds the cut-off threshold, the driven shaft automatically stalls, thereby preventing motor overload. Overall, this work provides an effective solution for enhancing the operational adaptability and transmission reliability of marine current energy conversion systems under variable flow conditions. Full article

This paper proposes a multi-objective optimization method based on response surface methodology and genetic algorithm to address the electromagnetic noise issue in external rotor permanent magnet synchronous motors. Theoretical analysis and 2D finite element simulation of electromagnetic force were conducted to identify the main orders of electromagnetic force; subsequently, through motor load and no-load tests, it was determined that the 6th-order radial electromagnetic force is the primary source of electromagnetic noise. Taking the 6th-order radial electromagnetic force, average torque, and torque ripple as optimization objectives, three key structural parameters were selected from eight optimization variables to construct a response surface model. The structural parameter optimization scheme for the motor was then obtained using a genetic algorithm. Finally, the optimization scheme obtained by the response surface method was validated under motor load conditions using two-dimensional finite element simulation; simulation results indicate that, compared to the original design, the optimized motor, exhibits a reduction in torque ripple by 65%, with the harmonic content of the radial air-gap flux density at the 1st, 3rd, 5th, and 7th orders decreasing by 8.7%, 6.4%, 12.5%, and 10.7%, respectively, and the 6th-order radial electromagnetic force reduced by 16.4%. Based on experimental identification of the dominant noise source, this reduction is expected to effectively suppress electromagnetic noise, which will be validated on a prototype in future work. Full article