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    <title>Transport Research International Documentation (TRID)</title>
    <link>https://trid.trb.org/</link>
    <atom:link href="https://trid.trb.org/Record/RSS?s=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" rel="self" type="application/rss+xml" />
    <description></description>
    <language>en-us</language>
    <copyright>Copyright © 2026. National Academy of Sciences. All rights reserved.</copyright>
    <docs>http://blogs.law.harvard.edu/tech/rss</docs>
    <managingEditor>tris-trb@nas.edu (Bill McLeod)</managingEditor>
    <webMaster>tris-trb@nas.edu (Bill McLeod)</webMaster>
    <image>
      <title>Transport Research International Documentation (TRID)</title>
      <url>https://trid.trb.org/Images/PageHeader-wTitle.jpg</url>
      <link>https://trid.trb.org/</link>
    </image>
    <item>
      <title>Experimental Analysis of Frictional Torque from Radial Ball Bearings</title>
      <link>https://trid.trb.org/View/2579379</link>
      <description><![CDATA[In this paper a method for experimental determination of frictional torque in radial ball bearings is proposed. For this purpose, an experimental stand is designed and manufactured which allows experimental determination of the frictional torque. A mathematical model is presented which allows the determination of frictional torque in bearings, namely the torque due to liquid lubrication and the torque due to rolling. This mathematical model is processed and numerical data are obtained, by theoretical method, which are compared with those determined experimentally. The obtained results are presented and discussed in the paper.]]></description>
      <pubDate>Mon, 13 Jul 2026 10:46:16 GMT</pubDate>
      <guid>https://trid.trb.org/View/2579379</guid>
    </item>
    <item>
      <title>Aspects of Planetary Transmissions Predesign</title>
      <link>https://trid.trb.org/View/2579372</link>
      <description><![CDATA[The paper presents some recommendations for the study of the possibilities offered by an existent kinematic scheme of a planetary transmission. First, some constructive characteristics of planetary units are obtained so that the realizable transmission ratios of the gearset to represent the best approximation of the wanted ratios for best performances. It is also presented a way to establish the magnitudes of the torques and powerflows that stress the gears, shafts, clutches and brakes.]]></description>
      <pubDate>Mon, 13 Jul 2026 10:46:16 GMT</pubDate>
      <guid>https://trid.trb.org/View/2579372</guid>
    </item>
    <item>
      <title>Predictive modeling of BLDC motor performance in UAV systems using ensemble learning</title>
      <link>https://trid.trb.org/View/2702880</link>
      <description><![CDATA[Accurate prediction of thrust and torque is essential for optimizing the performance, energy efficiency, and control of brushless direct current (BLDC) motors in unmanned aerial vehicles (UAVs). Traditional physics-based models often struggle to capture the nonlinear relationships between motor input parameters and aerodynamic outputs, prompting the exploration of data-driven approaches. This study evaluates the predictive capabilities of six ensemble learning algorithms, including Bootstrap Aggregating (Bagging), Adaptive Boosting (AdaBoost), Gradient Boosting Machine (GBM), Extreme Gradient Boosting (XGBoost), Categorical Boosting (CatBoost), and Stacked Generalization (Stacking), in modeling thrust and torque. Experimental data were obtained using a Tyto Robotics thrust stand designed for precise static performance testing of electric propulsion systems. Among the models, CatBoost exhibited the highest accuracy in thrust prediction with a coefficient of determination of 0.9873, a root mean square error (RMSE) of 7.0506, a mean absolute error (MAE) of 6.0610, and a mean absolute percentage error (MAPE) of 2.10%. In torque prediction, AdaBoost demonstrated superior performance, achieving an R2 of 0.9713, RMSE of 0.0018, MAE of 0.0013, and MAPE of 2.60%, effectively capturing complex electromechanical dynamics. In contrast, XGBoost underperformed in thrust prediction due to hyperparameter sensitivity, while Stacking showed limited generalization in torque estimation. Bagging and GBM delivered moderate and consistent results across both outputs. The findings underscore the potential of CatBoost and AdaBoost for robust predictive modeling of UAV propulsion systems, contributing to enhanced control and system design in autonomous flight applications.]]></description>
      <pubDate>Tue, 30 Jun 2026 09:45:03 GMT</pubDate>
      <guid>https://trid.trb.org/View/2702880</guid>
    </item>
    <item>
      <title>Analytical Magnetic Circuit Modeling and Parameter Estimation of a PMSM for Spatial Harmonics and Radial Forces Characterization</title>
      <link>https://trid.trb.org/View/2717280</link>
      <description><![CDATA[This paper presents an analytical model for three-phase Permanent Magnet Synchronous Motors (PMSMs) based on Magnetic Equivalent Circuits (MECs). The approach combines a reduced magnetic network, formulated in the complex domain to simplify the mathematical development, with an offline parameter estimation procedure systematically applied for different harmonic orders. This enables the model to capture the spatial dependence of permeance variations and reproduce inductance and magnetic flux nonlinearities, while maintaining generality, physical interpretability, and computational efficiency. Numerical simulations are compared with Finite Element (FE) results to validate the model’s ability to predict current and torque harmonics and the resulting radial electromagnetic forces, demonstrating its suitability for fast Noise, Vibration, and Harshness (NVH) analysis and vibroacoustic optimization.]]></description>
      <pubDate>Tue, 30 Jun 2026 08:51:20 GMT</pubDate>
      <guid>https://trid.trb.org/View/2717280</guid>
    </item>
    <item>
      <title>Parameter optimisation of heavy-duty vehicle wet clutch based on Kriging approximation model and multi-island genetic algorithm</title>
      <link>https://trid.trb.org/View/2677530</link>
      <description><![CDATA[In the transmission system of heavy-duty vehicles, when the friction pair of the wet clutch is in the separation condition, due to the viscous effect of the oil, the relative speed difference between the friction plate and the steel disc will generate the drag torque in the clearance of the friction pair and the drag power loss in wet clutch, which will cause a decrease in the transmission efficiency of the power system and an increase in the failure rate. Therefore, the fluid model of friction pair was established with composite groove as the research object. Based on the Kriging approximation model, eight groove parameters were selected as optimisation variables, and the minimum drag torque was taken as the optimisation objective. The multi-island genetic algorithm was used to optimise the structure parameters of the friction pair groove, the results showed that the optimised friction plate effectively improved the oil circulation.]]></description>
      <pubDate>Wed, 24 Jun 2026 13:22:07 GMT</pubDate>
      <guid>https://trid.trb.org/View/2677530</guid>
    </item>
    <item>
      <title>Development of Next Generation Sustainable Electric Traction Motors</title>
      <link>https://trid.trb.org/View/2581599</link>
      <description><![CDATA[The development of traction motors with easily recyclable rare-earth permanent magnets (PMs) is studied. The primary objective is to find means and technologies that enable the reuse of the PMs without extracting their elements. Both the motor design and PM assembly need to be aligned with this target. Especially, we are focusing on metallic encapsulation of the PMs to make them strong enough to tolerate the disassembly forces. First, we discuss the design, addressing the positioning of the encapsulated PMs to balance between the mechanical and electromagnetic requirements. Second, we present the first results on the encapsulation of the PMs for intact disassembly, elaborating on the materials, manufacturing via direct energy deposition, and visual inspection of the results. We aim to contribute to the emergence of the next generation less rare-earth-element-dependent, compact, and energy-efficient electric traction motors.]]></description>
      <pubDate>Thu, 18 Jun 2026 08:54:38 GMT</pubDate>
      <guid>https://trid.trb.org/View/2581599</guid>
    </item>
    <item>
      <title>High-Precision Nonlinear Semi-Analytical Model of High Torque Density 3-D Magnetic Circuit Permanent Magnet Motor in Aircraft Electric Propulsion Application</title>
      <link>https://trid.trb.org/View/2665607</link>
      <description><![CDATA[This article proposes a novel high-precision nonlinear semi-analytical model for the magnetic fields and the electromagnetic performance calculation of 3-D magnetic circuit permanent magnet motor (3DMCPMM) in aircraft electric propulsion applications, which can take the effects of the magnetic saturation nonlinearity and the permanent magnet (PM) end-leakage flux into account. The high torque density 3DMCPMM topology is first proposed, which can improve the output torque per unit weight via the 3-D magnetic circuit coupling. To simplify the computation, the 3-D magnetic circuit equivalent decoupling method is proposed for 3DMCPMM, which can convert the 3-D magnetic circuit into dual 2-D magnetic circuits. The 3DMCPMM analytic model is then proposed based on the harmonic subdomain approach, which can accurately predict the magnetic field distribution and the electromagnetic performance. Furthermore, using the equivalent magnetic circuit (EMC) model, the PM end leakage flux coefficient is proposed for the 3DMCPMM analytic model, which can eliminate the calculation error due to the PM end-leakage flux effect. The nonlinear iteration-based magnetic permeability is proposed for the 3DMCPMM analytic model, which can improve the analytic calculation accuracy by considering the magnetic saturation nonlinearity. A 630-N ⋅ m 3DMCPMM is designed and manufactured with the torque density of 25.37 N ⋅ m/kg. Simulation and experimental results show that the proposed semi-analytic model has an excellent electromagnetic prediction performance with a maximum calculation error of 4.62%, which can achieve the analytic calculation of 3-D magnetic circuit motor. The 3DMCPMM semi-analytical model is proposed for the first time, which lays the foundation for the 3DMCPMM rapid design and iterative optimization.]]></description>
      <pubDate>Wed, 17 Jun 2026 16:13:03 GMT</pubDate>
      <guid>https://trid.trb.org/View/2665607</guid>
    </item>
    <item>
      <title>An Energy-Efficient Torque Optimization Strategy With Field Weakening for a State Feedback Controller With Synchronous Reluctance Motor Drive</title>
      <link>https://trid.trb.org/View/2665596</link>
      <description><![CDATA[A trend for developing synchronous reluctance motors (SynRMs)-based drive systems is observed in the industry due to their simple and robust construction, with no rare Earth elements (REEs). These machines offer high efficiency and are based on easily available materials. Designing an energy-efficient control strategy is nontrivial because of the magnetic saturation phenomenon in the iron-based rotor. Outstanding dynamic drive performance can be achieved by applying a constrained full-state feedback controller (SFC). However, this structure cannot employ classical torque maximization strategies, leading to poor efficiency. Thus, a customized torque maximization strategy has to be designed for SFC-based angular velocity control systems to enable energy-efficient operation. An original torque maximization strategy for a SynRM drive is proposed for the SFC structure. Maximum torque operation is ensured by applying a customized torque maximization unit (TMU) with maximum torque per ampere (MTPA) and field weakening (FW) operation. MTPA is based on a precalculated trajectory using the machine’s model, implemented using an offline-trained artificial neural network; meanwhile, FW is based on a machine parameter-free approach with current phase shifting (CPS). The robustness of the CPS was analytically confirmed based on a small-signal analysis. The experimental results obtained confirm energy-efficient and stable operation of the system for both the MTPA and the FW operations. The proposed SFC-TMU structure is compared to a state-of-the-art lookup table (LUT)-based field-oriented control (FOC) cascade control structure (CCS). The given torque maximization trajectory is properly tracked and reveals superior efficiency, outperforming a classical LUT-based FOC-CCS strategy.]]></description>
      <pubDate>Wed, 17 Jun 2026 16:13:03 GMT</pubDate>
      <guid>https://trid.trb.org/View/2665596</guid>
    </item>
    <item>
      <title>Full-Torque Copper-Loss Minimum Adaptive Fault-Tolerant Control of Dual Three-Phase PMSM Under Open-Phase Faults</title>
      <link>https://trid.trb.org/View/2665590</link>
      <description><![CDATA[A full-torque copper-loss minimum adaptive fault-tolerant control (FTCM-AFTC) method is proposed in this article for a dual three-phase permanent magnet synchronous motor (DTP-PMSM) drive system under an open-phase fault. In the proposed FTCM-AFTC, a unified control architecture is constructed to realize seamless operation under healthy and fault conditions. The proposed FTCM-AFTC method can smoothly transition after fault occurrence without additional hardware. In addition, the method can dynamically adjust FTCM according to torque demand to ensure optimal operation efficiency. Finally, the effectiveness of the proposed FTCM-AFTC method is verified by the experimental results.]]></description>
      <pubDate>Wed, 17 Jun 2026 16:13:03 GMT</pubDate>
      <guid>https://trid.trb.org/View/2665590</guid>
    </item>
    <item>
      <title>Magnet Arrangement Design and Comprehensive Analysis of a Split-Tooth Permanent Magnet Arc Motor Based on Poynting Theory</title>
      <link>https://trid.trb.org/View/2665589</link>
      <description><![CDATA[This article proposes a new split-tooth permanent magnet (PM) arc motor with dual PM excitation. The property of the slot-PMs allows the motor to have good overload capacity, while the flux-reversal PMs can compensate for the torque in slot-PM motors under light load. This PM combination ensures that the proposed motors have high torque under different load conditions. Two different magnet arrangements with different rotor poles are investigated through flux harmonic analysis to obtain higher output torque. Two optimal motor types are selected and compared with two benchmark motors that only have flux-reversal PMs. In order to analyze the torque components of the four motors, a Poynting theory-based torque calculation method is proposed, and a more detailed derivation is carried out. After optimization and comprehensive torque performance comparison, the proposed motor with five rotor poles in a single motor unit is manufactured and tested. The finite element and experimental results validate the superiority of the proposed motor.]]></description>
      <pubDate>Wed, 17 Jun 2026 16:13:03 GMT</pubDate>
      <guid>https://trid.trb.org/View/2665589</guid>
    </item>
    <item>
      <title>Current–Torque Fusion Efficient Multiscale Convolutional Neural Network for Local Demagnetization Fault Diagnosis in PMSM Drive Based on Limited Data Samples</title>
      <link>https://trid.trb.org/View/2665585</link>
      <description><![CDATA[Permanent magnet synchronous motor (PMSM) operates under harsh environmental conditions and complex working regimes, making it prone to irreversible local demagnetization faults (LDFs). Classical irreversible LDF diagnosis methods primarily rely on signal processing- or model-based indirect identification techniques, which continue to face challenges in achieving satisfactory accuracy and robustness. In contrast, a strategy via multisource heterogeneous information fusion can more accurately capture the demagnetization behavior of permanent magnets, making it a suitable solution for further enhancing the safety and reliability of motor drive systems. However, in practical industrial scenarios, the scarcity of samples hinders diagnostic models from fully learning the deep characteristic patterns of different demagnetization fault modes, limiting further improvements in their generalization capability and diagnostic accuracy. To address this issue, a data-driven fault diagnosis scheme for local demagnetization is proposed. In the proposed scheme, the stator current and torque are compressed and reconstructed by using compressed sensing (CS) to overcome the problem of scarce fault data. Furthermore, a visual heterogeneous information fusion strategy is proposed. This strategy visualizes time-series data by using a 2-D mapping algorithm and fuses multisource visual data based on the visual saliency map and weighted least squares (VSM-WLS), achieving the enhancement and complementarity of demagnetization features. Finally, the efficient multiscale convolutional network (EMC-Net) for fault diagnosis and identification is designed with ConvNeXt as its backbone. By integrating the efficient multiscale attention (EMA) mechanism, the network adaptively captures fault features across different scales, significantly improving diagnostic performance. Experimental results show that the proposed scheme achieves 99.4% diagnostic accuracy and successfully identifies various demagnetization patterns across three prototypes.]]></description>
      <pubDate>Wed, 17 Jun 2026 16:13:03 GMT</pubDate>
      <guid>https://trid.trb.org/View/2665585</guid>
    </item>
    <item>
      <title>Design and Analysis of a Novel Consequent-Pole Interleaved Hybrid Magnet Memory Machine</title>
      <link>https://trid.trb.org/View/2665577</link>
      <description><![CDATA[The conventional hybrid magnet memory machine (C-HMMM) suffers from several drawbacks, including excessive permanent magnet (PM) usage and high associated costs. Moreover, it faces inherent performance trade-offs between high torque density and wide-speed-range operation, as well as between flux stabilization and flux regulation (FR) capabilities. To address these issues, this article proposes a novel motor topology: the consequent-pole interleaved hybrid magnet memory machine (CI-HMMM) with an eight-pole, 48-slot configuration. This structure is designed to strike a balance between the aforementioned conflicting performance requirements. Compared to the C-HMMM, the CI-HMMM significantly extends the FR range while maintaining a high torque output. Furthermore, an equivalent simplified magnetic circuit model of the machine was developed, which demonstrates that the proposed motor structure offers a superior FR range compared to C-HMMM. The study further reveals that the FR range is influenced by different parameters under various magnetic circuit configurations. Based on insights into how key parameters impact electromagnetic performance, a comprehensive design optimization of the CI-HMMM is conducted. The optimized CI-HMMM is then benchmarked against the C-HMMM through comparative analysis. Finally, a CI-HMMM prototype is fabricated and experimentally tested, which confirms the accuracy of the finite element (FE) analysis.]]></description>
      <pubDate>Wed, 10 Jun 2026 13:40:31 GMT</pubDate>
      <guid>https://trid.trb.org/View/2665577</guid>
    </item>
    <item>
      <title>Unbalanced Load Torque Compensation for Single-Rotary Compressors Based on Novel Magnetic Force Mechanisms in EVs and HEVs</title>
      <link>https://trid.trb.org/View/2665576</link>
      <description><![CDATA[Single-rotary compressors (SRCs) characterize a simple mechanical structure, low cost, and strong robustness, which are widely used in air-conditioning systems of EVs and HEVs. However, there is an inherent unbalanced load torque during the whole suction and exhausting process in SRCs, leading to a significant rotating speed fluctuation and hence serious vibration and noise issues. In this article, the properties of the unbalanced load torque in SRCs are studied in detail, and the corresponding magnetic force mechanisms (MFMs) for load torque compensation are proposed for the first time. The MFMs can be accommodated both inside and outside the drive motor, considered as integrated MFMs (IMFMs) and separated MFMs (SMFMs), respectively. It is found that both IMFM and SMFM can effectively reduce the load torque ripple, especially the dominant 1st harmonic, resulting in a steady rotating speed via finite-element analysis (FEA). Compared with IMFMs, SMFM exhibits flexible topologies without rebuilding of the drive motor and the decrease in efficiency. The SMFM prototype is built and tested. From the experimental results, it is found that the vibration and noise of the SRC are significantly improved, with 0.8% improvement in the energy efficiency after SMFM torque compensation. Compared with the conventional torque compensation by machine control (MC), the proposed SMFM torque compensation can exhibit competitive vibration and noise with faster response, especially a 2.1% improvement in the overall energy efficiency. It should be emphasized that the proposed SMFM can be the design guideline for electric machines in applications of periodic fluctuating loads.]]></description>
      <pubDate>Wed, 10 Jun 2026 13:40:31 GMT</pubDate>
      <guid>https://trid.trb.org/View/2665576</guid>
    </item>
    <item>
      <title>Field-Modulation Electrical Machines: Origin, Unification, and Development</title>
      <link>https://trid.trb.org/View/2665575</link>
      <description><![CDATA[The air-gap field harmonics were considered to undermine the performance of electrical machines for more than a century. Since the proposal of general air-gap field-modulation theory (GAFMT) in 2017, the magnetic field-modulation effect (MFME) has received unprecedented attention. Harmonics are proven to be no longer a hindrance, but a benefit by artificial design. Accompanied field-modulation electrical machines (FMEMs) that work relying on harmonics are becoming increasingly popular and expected to satisfy the hunger for high torque and high efficiency simultaneously in the modern industry. In this review, the development histories of FMEMs, with particular reference to brushless doubly fed machines (BDFMs), coaxial magnetic gears (CMGs) and magnetically geared machines (MGMs), permanent magnet Vernier (PMV) machines, and stator-PM machines, are presented. Then, the necessity of proposing the GAFMT for harmonic usage is highlighted. The latest developments of FMEMs, including theoretical, technological, and application aspects, are systemically analyzed. Finally, challenges to be addressed are discussed.]]></description>
      <pubDate>Wed, 10 Jun 2026 13:40:31 GMT</pubDate>
      <guid>https://trid.trb.org/View/2665575</guid>
    </item>
    <item>
      <title>Tangential-Rib-Free SynRel Machine With Improved Torque Density and Manufacturability for an Electric Assist Turbocharger</title>
      <link>https://trid.trb.org/View/2665568</link>
      <description><![CDATA[The synchronous reluctance (SynRel) machine designed for any high-speed application is found to exhibit an inferior saliency ratio due to the increased total rib thickness for handling the centrifugal force. Therefore, this article aims to identify a new rotor topology that offers an improved saliency ratio for high-speed SynRel machines. Based on this, a tangential rib-free SynRel rotor is recognized as the peerless SynRel configuration for all high-speed operations. A 3.5-kW, 60-kr/min SynRel machine is designed for an electric assist turbocharger (EAT) to ascertain the superior performance of the tangential rib-free rotor over its conventional counterparts. The tangential rib-free SynRel machine is found to achieve a minimum improvement of 16% in the electromagnetic torque performance compared to other conventional rotor topologies. In addition, the tangential rib-free SynRel machine is subjected to static structural, rotordynamic, and thermal analysis to validate its rigidity during high-speed operation. Finally, the tangential-rib-free SynRel machine is fabricated, and its performance is experimentally validated.]]></description>
      <pubDate>Tue, 09 Jun 2026 14:43:23 GMT</pubDate>
      <guid>https://trid.trb.org/View/2665568</guid>
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