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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>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>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>Optimized Slot Design of PMVM Aiming for Reduced Back EMF Total Harmonic Distortion</title>
      <link>https://trid.trb.org/View/2665572</link>
      <description><![CDATA[Permanent magnet vernier machine (PMVM) are known for high torque density enabled by magnetic field modulation, making them suitable for electric vehicle (EV) applications. However, harmonics in the back electromotive force (EMF) have been shown to degrade torque quality and increase the peak-to-peak torque ripple. In this study, the back EMF of PMVM is analyzed to achieve low total harmonic distortion (THD). The operating principle is examined, and the relationship between the fundamental and harmonic components is derived. The conflict between fundamental enhancement and harmonic suppression is revealed, requiring a trade-off design strategy. Reduced slot opening is found to increase the slot-opening factor, which in turn amplifies both fundamental and high-order harmonics. To address this, a new topology is adopted capable of suppressing high-order harmonics while maintaining high fundamental component. Magnetic field modulator with an inverted trapezoidal slot and a multidegree-of-freedom tooth structure is proposed. With appropriate topology selection, the fundamental can be enhanced while harmonics are minimized, reducing back EMF THD. The effectiveness of the proposed method is validated through experiments on two prototypes.]]></description>
      <pubDate>Wed, 10 Jun 2026 13:40:31 GMT</pubDate>
      <guid>https://trid.trb.org/View/2665572</guid>
    </item>
    <item>
      <title>Tradeoff Between Radial Force and Tangential Force for Multiphase Permanent Magnet Machines With Harmonic Current Injection</title>
      <link>https://trid.trb.org/View/2665566</link>
      <description><![CDATA[Harmonic currents are commonly employed in multiphase permanent magnet (PM) machines to enhance the output torque, which essentially improves the tangential force. However, as the radial force (RF) is also affected by the harmonic currents, high noise and vibration may be induced. This article systematically investigates the dual impacts of harmonic currents on both radial and tangential force characteristics. Analytical derivations reveal that armature-induced RFs correlate with current phase, enabling antiphase compensation between current-induced and inherent RFs to suppress vibrations. However, the optimal phase angles for vibration minimization and torque maximization are inherently mismatched. A detailed parametric analysis is performed through finite element simulations on a five-phase PM machine with a ten-slot/eight-pole configuration, employing third-harmonic current injection with varying amplitudes. The amplitude–phase relationships of both tangential and RF components are quantitatively examined. Results demonstrate the fundamental compromise between torque improvement and vibration reduction in current injection strategies. Experimental validation is subsequently conducted through prototype testing, with measured vibration acceleration and output torque data confirming the analytical findings.]]></description>
      <pubDate>Tue, 09 Jun 2026 14:43:23 GMT</pubDate>
      <guid>https://trid.trb.org/View/2665566</guid>
    </item>
    <item>
      <title>No-Load Analytical Model of STPM Motor With Asymmetric Modular Rotor Under Mixed Eccentricity for In-Wheel Traction Applications</title>
      <link>https://trid.trb.org/View/2665564</link>
      <description><![CDATA[To reduce the usage of rare-earth permanent magnet (PM), this article proposes a novel asymmetric modular rotor spoke-type PM (MR-STPM) motor for in-wheel lightweight traction applications. The analytical model is established to investigate the operation principle and the no-load performance of this type of motor. First, the evolution process of the geometric topology of the STPM motor is introduced. Then, the analytical models of cogging torque and open-circuit back-electromotive force (back EMF) for symmetric/asymmetric MR-STPM motors are developed based on the general airgap field modulation theory (AFMT). Furthermore, the effect of mixed eccentricity (ME) on the aforementioned performances, attributable to manufacturing tolerances, is also investigated. With the help of analytical models and finite element analysis (FEA), the harmonic behaviors are revealed comprehensively. Finally, a prototype motor is manufactured and tested, and the measured results have a good agreement with the analytical models and FEA predicted results.]]></description>
      <pubDate>Tue, 09 Jun 2026 14:43:23 GMT</pubDate>
      <guid>https://trid.trb.org/View/2665564</guid>
    </item>
    <item>
      <title>Optimization of Amorphous Alloy Axial-Modular Flux-Switching Permanent Magnet Machine Considering Edge Degradation Uncertainty</title>
      <link>https://trid.trb.org/View/2665544</link>
      <description><![CDATA[This article proposes a multiobjective optimization considering edge degradation uncertainty design methodology for amorphous alloy axial-modular flux-switching permanent magnet (AM-FSPM) machines. To eliminate the uncertainty effects associated with edge degradation, the harmonic distributions of the air-gap magnetic field are deduced with an effect factor for edge degradation. Based on the stochastic characteristics of edge degradation, an optimization function considering edge degradation uncertainty is established and optimized with the standard deviations of torque and torque ripple as the objective functions. Then, a comparison between the optimization design considering edge degradation uncertainty and the optimization design only considering edge degradation shows that the proposed method effectively mitigates the impact of edge degradation uncertainty. Finally, a prototype is manufactured and tested to further validate the effectiveness of the proposed approach.]]></description>
      <pubDate>Fri, 05 Jun 2026 16:41:22 GMT</pubDate>
      <guid>https://trid.trb.org/View/2665544</guid>
    </item>
    <item>
      <title>A Novel Compound Fast Nonsingular Terminal Sliding Mode Disturbance Rejection Control for Multiunit Distributed Permanent Magnet Arc Motor</title>
      <link>https://trid.trb.org/View/2665535</link>
      <description><![CDATA[This article proposes a novel compound fast nonsingular terminal sliding mode disturbance rejection control strategy for permanent magnet arc motors (PMAMs), which simultaneously enhances speed tracking accuracy and disturbance rejection performance. The primary contribution of this study lies in the development of a multilayer fast nonsingular terminal sliding mode controller (MFNTSMC) that effectively addresses the slow convergence issues associated with conventional terminal sliding mode control (SMC) when it is far from the equilibrium point, and eliminates chattering through the introduction of innovative multilayer terminal attraction factors. The proposed MFNTSMC guarantees finite-time convergence of the speed tracking error, regardless of initial conditions. In addition, in order to combat high-frequency nonlinear unmodeled disturbances inherent in PMAMs, which are caused by high pole-pair configurations and end effects induced by segmented structures, a novel high-order global fast-convergent nonlinear disturbance observer (HGFNDO) is integrated with MFNTSMC for accurate lumped disturbance estimation. The main innovation is the novel switching mechanism incorporated into both the controller and the observer, which significantly enhances convergence speed and can be extended to any order without imposing a substantial computational burden. The closed-loop stability of the system is rigorously proven using the Lyapunov theory. Experimental results verify the effectiveness and superiority of the proposed strategy.]]></description>
      <pubDate>Thu, 04 Jun 2026 11:57:21 GMT</pubDate>
      <guid>https://trid.trb.org/View/2665535</guid>
    </item>
    <item>
      <title>Fault Detection of Microcracks in Permanent Magnet of Permanent Magnet Synchronous Linear Motors Based on Magnetic Surface Information Time-Domain and Gray Texture Features</title>
      <link>https://trid.trb.org/View/2665526</link>
      <description><![CDATA[A novel method for the rapid and accurate detection of microcracks in the secondary permanent magnets of permanent magnet synchronous linear motor (PMSLM) is proposed in this article, which combines the time-domain characteristics and gray-level texture features of microcracks. First, an analytical model of the air-gap magnetic field for a permanent magnet with microcracks is established. This model demonstrates that the surface magnetic field information of the permanent magnet can be utilized to detect microcracks. Second, the magnetic surface information matrix (MSIM) is constructed. After extracting the time-domain characteristics, the matrix is transformed into a grayscale image to facilitate the extraction of grayscale co-occurrence matrix features that are indicative of microcrack characteristics. Subsequently, the fluctuation rate of thrust caused by microcracks is utilized as the basis for classification. The SHapley Additive exPlanation (SHAP) method is introduced to demonstrate the correlation between the aforementioned feature quantities and the severity of microcracks, thereby enhancing the interpretability of the deep learning model. Finally, a classification model for microcracks in permanent magnets is established using the Transformer algorithm and is compared with WOA-MSKCNN and WOA-PNN. Simulation experiments and prototype experiments have proven that the method proposed in this article has the highest recognition rate for microcracks in PMSLM under both noisy and normal environments while also having the shortest computation time.]]></description>
      <pubDate>Tue, 02 Jun 2026 13:56:53 GMT</pubDate>
      <guid>https://trid.trb.org/View/2665526</guid>
    </item>
    <item>
      <title>A Precise Semianalytical Model for Efficiently Calculating the Magnetic-Track Coupled Forces in a Superconducting Electrodynamic Suspension Train</title>
      <link>https://trid.trb.org/View/2658882</link>
      <description><![CDATA[In superconducting electrodynamic suspension (EDS) trains, the magnetic-track coupled forces arise from the electromagnetic interaction between the onboard magnets and track coils, enabling the train’s suspension, guidance, and propulsion. These forces can be determined based on the mutual inductance between the magnets and track coils. This paper presents a novel segregated integration approach for accurately and efficiently calculating mutual inductance. Building on this approach, we develop a semianalytical model capable of simulating an infinitely long track to compute the magnetic-track coupled forces in an EDS train with high accuracy and efficiency. To validate the model, we conducted force measurements on a superconducting EDS prototype and compared the results with our semianalytical model, which demonstrated a relative error of less than 3%. Additionally, we performed a systematic evaluation of the semianalytical model by comparing it with a finite element model and a widely adopted analytical model based on Neumann’s formula to thoroughly assess its accuracy and applicability. The results show that, compared to the finite element model, our model enhances computational speed by two orders of magnitude while maintaining an accuracy on the order of  $10^{-3}$ . Furthermore, it surpasses the analytical model in both accuracy and efficiency. Using this developed model, we investigated the forces in an EDS train with a stepped onboard magnet. The results show that employing stepped magnets can suppress the first harmonic of the suspension force by 65% without compromising the train’s suspension and propulsion capabilities.]]></description>
      <pubDate>Thu, 28 May 2026 17:09:35 GMT</pubDate>
      <guid>https://trid.trb.org/View/2658882</guid>
    </item>
    <item>
      <title>A Novel Intelligent Operation State Recognition Approach for High-Temperature Superconducting Levitator of Maglev Vehicle Based on Thermal-Vibration Fusion Method</title>
      <link>https://trid.trb.org/View/2659030</link>
      <description><![CDATA[The change in the levitation state of the superconducting levitator will directly affect the operation of the high temperature superconducting (HTS) pinning maglev vehicle. The internal temperature of the HTS bulks inside the superconducting levitator and external vibration acceleration significantly affect its levitation performance. However, the traditional state detection method uses the levitation height monitoring to evaluate the state, which cannot accurately measure the levitation state of superconducting levitator. Therefore, an intelligent method combining wavelet packet transform (WPT) and one-dimensional convolutional neural network (1D-CNN) is proposed in this paper, which integrates vibration acceleration and temperature rise. Firstly, based on the HTS maglev dynamical experimental data of the SCML-03 device, an accurate finite element model is constructed. Then, the dynamic thermal-vibration dataset of the superconducting levitator at operating speeds of 100 km/h-620 km/h is obtained. The WPT is employed to extract the energy features of vibration acceleration, the energy features and temperature are used as input for recognition model. Finally, the state recognition result is output, with an accuracy of 100%. The work can provide a preliminary research foundation for the online monitoring and fault diagnosis of future HTS maglev train.]]></description>
      <pubDate>Thu, 28 May 2026 17:09:32 GMT</pubDate>
      <guid>https://trid.trb.org/View/2659030</guid>
    </item>
    <item>
      <title>Novel In-Slot Direct Cooling Structure of Concentrated Winding Permanent Magnet Electrical Machine for Aerospace Propulsion</title>
      <link>https://trid.trb.org/View/2665496</link>
      <description><![CDATA[With the development of high-power-density electrical machines, in-slot direct cooling has become a key method to overcome power density limitations. To further enhance the thermal performance of stator oil direct cooling, three novel cooling structures are proposed and systematically compared, with the optimal structure being identified. The structure introduces tooth- and wedge-side oil paths to increase the contact area between the winding and coolant, and further incorporates oil-blocking teeth at the slot bottom to adjust the flow rate and velocity distribution of different paths. First, three novel direct cooling structures and a conventional structure are introduced, and their coolant flow paths are analyzed. To simplify modeling, a thermal conductivity equivalent model for formed litz wires is developed and validated. In addition, electromagnetic and mechanical performance are evaluated. Finite element results show stable torque across all designs, while harmonic response analysis indicates that the added features enhance stiffness and reduce vibration near excitation frequencies. Computational fluid dynamic (CFD) simulations are then conducted to assess flow distribution, coolant velocity, and temperature under various conditions. Results show that the proposed structures effectively reduce winding temperature rise. A stator tooth-slot module is also tested, and the experimental results align well with simulations, validating the analysis and thermal model.]]></description>
      <pubDate>Thu, 28 May 2026 10:47:37 GMT</pubDate>
      <guid>https://trid.trb.org/View/2665496</guid>
    </item>
    <item>
      <title>Power-Dense Integrated Motor Drive Using a WBG-Enabled Current-Source Inverter for EV Traction Applications</title>
      <link>https://trid.trb.org/View/2665491</link>
      <description><![CDATA[This article explores the major design considerations associated with the development of a high-power-density integrated motor drive (IMD) utilizing wide bandgap (WBG) power switches in a current-source inverter (CSI) for electric vehicle (EV) traction applications. The rationale for adopting the CSI for this application is presented, followed by a discussion of key design issues associated with all major IMD components, including the CSI itself, dc/dc converter, passive components, control algorithms, CSI-based electric motor, and the cooling system. By focusing attention on the IMD physical integration details, the optimized power electronics and machine can achieve active power densities of 115 kW/L and 55.6 kW/L, respectively. The performance of the proposed IMD system under different operating conditions is carefully evaluated using a combination of simulation and experimental test results. These results provide insights into the advantages that high-power-density IMDs based on CSI and WBG devices can provide for future EV traction drive systems, as well as the remaining technical challenges.]]></description>
      <pubDate>Thu, 28 May 2026 10:47:37 GMT</pubDate>
      <guid>https://trid.trb.org/View/2665491</guid>
    </item>
    <item>
      <title>Modeling and Investigation of Asymmetric Rotor Eccentricities in Double-Rotor Single-Stator Axial-Flux Permanent Magnet Machines</title>
      <link>https://trid.trb.org/View/2659235</link>
      <description><![CDATA[The dual-rotor single-stator axial-flux permanent magnet machine (DRSS AFPMM) demonstrates superior power density and torque output capabilities through dual air-gap topology and compact magnetic circuit design. However, the additional rotor introduces increased probability and complexity of eccentricity faults, manifesting as spatiotemporal asynchrony in dual air-gap magnetic flux density (MFD) distributions. Conventional single-rotor eccentricity models prove inadequate for characterizing asymmetric faults in this specialized architecture. A novel analytical modeling (AM) framework is developed for asymmetric eccentricity in DRSS AFPMMs, employing a coordinated representation system of phase displacement and normalized amplitude. This methodology maps dual-rotor eccentricity states to compound air-gap field modulation processes: rotor axis eccentricities (RAXEs) are described through dynamic pole-pitch correction modeling, while rotor angular eccentricities (RAGEs) are translated into air-gap permeance amplitude modulation principles. Subsequent analysis of the electromagnetic performance under asymmetric eccentricity conditions was conducted by double air-gap offset field superposition. A loss coefficient is established to evaluate flux linkage reduction under RAXE. Furthermore, a dual air-gap MFD deviation model is formulated to analyze back electromotive force (EMF) attenuation caused by magnetic excitation misalignment fault (MEMF). The proposed methodology is validated through finite-element analysis (FEA) and experimental testing, confirming its effectiveness in predicting fault-induced electromagnetic variations.]]></description>
      <pubDate>Tue, 26 May 2026 11:56:24 GMT</pubDate>
      <guid>https://trid.trb.org/View/2659235</guid>
    </item>
    <item>
      <title>Comprehensive Comparative Analysis of High-Speed Permanent Magnet Motors With Different Winding Structures</title>
      <link>https://trid.trb.org/View/2659232</link>
      <description><![CDATA[There are three main types of winding structures for high-speed permanent magnet motors: double-layer lap winding, double-layer concentric winding, and toroidal winding. Different winding structures have different multiphysics properties. For example, although the toroidal winding can effectively improve the rotor dynamic characteristics, the loss and temperature characteristics would become worse. Unfortunately, current research on high-speed permanent magnet motors is mainly based on double-layer lap winding structures, lacking a comprehensive analysis of the multiphysical characteristics of the three winding structures. The quantitative impact of each winding structure on the various performance parameters of high-speed permanent magnet motors is unclear. Therefore, this article comprehensively compares the electromagnetic characteristics, loss characteristics, rotor dynamics characteristics, and temperature characteristics of three winding structures and finally obtains the quantitative impact of the three winding structures on various performance indicators.]]></description>
      <pubDate>Tue, 26 May 2026 11:56:24 GMT</pubDate>
      <guid>https://trid.trb.org/View/2659232</guid>
    </item>
    <item>
      <title>Research of Dislocation and Bending Angle Effects on EDS Dynamic Characteristics Based on Real-Time Coupling Calculation Method</title>
      <link>https://trid.trb.org/View/2659198</link>
      <description><![CDATA[There are notable differences between electrodynamic suspension (EDS) and wheel–rail systems, making existing wheel–rail irregularity research inapplicable to EDS. This study examines the correlation between deterministic irregularities, such as dislocation and bending angles, and dynamic characteristics. These irregularities are divided into type-I (due to bridge length) and type-II (due to sidewall length). The modified electromagnetic force (MEMF) model, refined three-group trains (RTGTs) model, and magnetic–electric–mechanical coupling method are developed in this article. The analysis indicates that dislocation and bending angles primarily affect bogie vibration while minimally impacting the carbody. The study assesses the dynamics at speeds of 200, 400, and 600 km/h, offering recommended limit values. Recommendations for construction and maintenance include as follows: 1) vertical irregularity management order: D-II-z, D-I-z, BA-II-z, and BA-I-z and 2) lateral irregularity management order: D-I-y, D-II-y, BA-I-y, and BA-II-y (letter meaning—I: Type-I, II: Type-II, D: dislocation, BA: bending angle, z: vertical, and y: lateral).]]></description>
      <pubDate>Tue, 26 May 2026 11:56:23 GMT</pubDate>
      <guid>https://trid.trb.org/View/2659198</guid>
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