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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" />
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    <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>Multibody Dynamic Analysis of Belt-Type CVT Systems in Two-Wheelers: A Study on Slip, Misalignment, and Transmission Efficiency</title>
      <link>https://trid.trb.org/View/2663327</link>
      <description><![CDATA[More efficient drivetrain technologies are in greater demand in the two-wheeler market as a result of the introduction of BS6.2 emission standards. In order to satisfy these performance and regulatory requirements, Continuously Variable Transmission (CVT) systems, which are renowned for their stepless gear shifting and increased fuel efficiency, are being given more and more consideration. However, because CVT is nonlinear and multibody dynamic, accurately predicting its behavior is still a difficult task.With an emphasis on variables like belt slip, pulley misalignment, and transmission efficiency, this study provides a thorough multibody dynamic analysis of a belt-type CVT system used in two-wheelers. High-fidelity analysis of the belt-pulley interaction under various load and speed conditions is now possible thanks to the development of a novel modeling methodologyThe method makes early design validation easier, minimizes iterations of physical prototyping and helps to maximize system performance. This study supports the automotive industry's drive for affordable and emission-compliant vehicle development by offering a strong framework for virtual validation of CVT systems under actual operating conditions.]]></description>
      <pubDate>Mon, 02 Feb 2026 16:36:54 GMT</pubDate>
      <guid>https://trid.trb.org/View/2663327</guid>
    </item>
    <item>
      <title>Optimal Control Strategy for Dual-Motor EVs with CVT: Comparison of Simulation of Steady-State and Dynamic Programming Methods</title>
      <link>https://trid.trb.org/View/2608417</link>
      <description><![CDATA[This study investigates an optimal control strategy for a battery electric vehicle (BEV) equipped with a high-speed motor and a continuously variable transmission (CVT). The proposed dual-motor powertrain model activates only one motor at a time, with Motor A routed through a CVT and Motor B through a fixed gear. To improve energy efficiency, two optimization methods are evaluated: a quasi-steady-state map-based approach and a dynamic programming (DP) method. The DP approach applies Bellman’s principle to derive the globally optimal CVT ratio and motor torque trajectory over the WLTC cycle. Simulation results demonstrate that the DP method significantly improves overall efficiency compared to traditional control logic. Furthermore, the study proposes using DP-derived maps to refine practical control strategies, offering a systematic alternative to conventional experimental calibration.]]></description>
      <pubDate>Tue, 14 Oct 2025 10:35:52 GMT</pubDate>
      <guid>https://trid.trb.org/View/2608417</guid>
    </item>
    <item>
      <title>Effect of Power Source and Transmission Mechanism on WLTC Electric Consumption of BEV</title>
      <link>https://trid.trb.org/View/2561948</link>
      <description><![CDATA[The study of changing combination of motor/generator and transmission is actively conducted to improve the specific electric consumption of BEV. In this study, OpenModelica model provided by TRAMI was used to predict the specific electric consumption in both steady run and WLTC cycle with changing maximum motor speed, transmission system, and number of gear speed. Sensitivity analysis was also conducted to examine the factors that affect the efficiency improvement of electric vehicles. As a result, it was quantitatively found that i) WLTC ranking does not necessarily accord with steady one, ii) the ring gear output is good when using planetary gear system and iii) CVT shows high mechanical efficiency by keeping low input speed and wide ratio-coverage and the optimization of shift map will be required, and iv) a combination of 2 motor and multi-speed is the best in specific electric consumption.]]></description>
      <pubDate>Tue, 12 Aug 2025 10:18:31 GMT</pubDate>
      <guid>https://trid.trb.org/View/2561948</guid>
    </item>
    <item>
      <title>A New Electrified Planetary Gear Set - The Cost- and Fuel-Efficient Alternative to Continuously Variable Transmissions</title>
      <link>https://trid.trb.org/View/2571739</link>
      <description><![CDATA[In order to mitigate the effects of climate change, the global transport sector, one of the largest emitters of CO2, needs to drastically reduce its emissions. Although hybridization and electrification are becoming increasingly popular as a solution for a variety of applications, their use in two- and three-wheelers, as well as in recreational and powersports vehicles, remains limited due to their high costs and complexity compared to conventional drivetrains with continuously variable transmissions (CVTs). Despite their affordability and simplicity, CVTs suffer from low mechanical efficiency, with transmission losses ranging from 20–50 %, highlighting a significant opportunity for improvement. In response to these limitations, this study presents the development and experimental evaluation of an electrified planetary gear set (ePGS) in a lightweight off-road vehicle. It is designed to overcome the efficiency limitations of CVTs while maintaining high driving comfort and low system complexity, as well as enhancing performance and fuel efficiency. The system design followed a structured approach, beginning with a morphological analysis and multi-criteria evaluation to refine potential drivetrain concepts. The final concept is characterized by its exceptionally compact design, which is achieved despite the use of commercial-off-the-shelf components. The functionality of the concept was validated through a prototype transmission that is tested in a series of driving scenarios, both on the road and on a chassis dynamometer. The results demonstrated a 17 % reduction of fuel consumption relative to the original vehicle that was equipped with a CVT, despite the absence of access to the engine control unit. These findings highlight the great potential of the ePGS system as a cost-effective, fuel efficient alternative for conventional CVT powered vehicles.]]></description>
      <pubDate>Tue, 08 Jul 2025 10:41:05 GMT</pubDate>
      <guid>https://trid.trb.org/View/2571739</guid>
    </item>
    <item>
      <title>Fatigue Strength Improvement for CVT Metal Belt by Ring Mesh</title>
      <link>https://trid.trb.org/View/2556920</link>
      <description><![CDATA[The fatigue strength of the mesh on the inner ring surface of the CVT metal belt was determined by ultrasonic fretting tests and low-torque high-tension loading mode. In the low-torque, high-tension loading mode, the cracks generated at the apex of the mesh geometry passed through the grooves of the mesh geometry, which arrested the crack propagation and increased the fatigue strength.]]></description>
      <pubDate>Thu, 26 Jun 2025 16:12:48 GMT</pubDate>
      <guid>https://trid.trb.org/View/2556920</guid>
    </item>
    <item>
      <title>Changes of Shifting Rate of Metal V-Belt Type CVT during Speed Up/Down under Quasi-Idle Loading Condition</title>
      <link>https://trid.trb.org/View/2547896</link>
      <description><![CDATA[The objective of this experimental study was to investigate the change of shifting rate of metal V-belt type CVT during speed up/down under quasi-idle loading condition. Changes in the rotational speeds of the driving and driven pulleys were simultaneously measured by the rotational speed sensors installed on the driving and driven shafts during speed up/down shifting, respectively. In addition, the interaxial force applied to the driving and driven pulleys was measured by a load cell. The shifting rate was defined as the ratio of the calculated radial displacement to the tangential displacement of the belt in the pulley groove. This study found that the shifting rate was determined not only by the slippage between the pulley and the belt element, but also by the elastic deformation of the belt element in the pulley groove. The power transmission performance was improved when the elastic deformation was small even though radial slippage between the pulley and the belt element was increased when quick shifting was achieved by increasing the applied low thrust force (which was defined as the lower thrust force than the other one).]]></description>
      <pubDate>Tue, 29 Apr 2025 15:53:21 GMT</pubDate>
      <guid>https://trid.trb.org/View/2547896</guid>
    </item>
    <item>
      <title>A Power Split eCVT Hybrid for Sustainable Urban Mobility</title>
      <link>https://trid.trb.org/View/2547847</link>
      <description><![CDATA[The main drivers for powertrain electrification of two-wheelers, motorcycles and ATVs are increasingly stringent emission and noise limitations as well as the upcoming demand for carbon neutrality. Two-wheeler applications face significantly different constraints, such as packaging and mass targets, limited charging infrastructure in urban areas and demanding cost targets.Battery electric two wheelers are the optimal choice for transient city driving with limited range requirements. Hybridization provides considerable advantages and extended operation limits. Beside efficiency improvement, silent and zero emission modes with solutions allowing fully electric driving, combined boosting enhances performance and transient response.In general, there are two different two-wheeler base categories for hybrid powertrains: motorcycles featuring frame-integrated internal combustion engine (ICE) and transmission units, coupled with secondary drives via chain or belt; and scooters equipped with integral single-sided swingarm power units, featuring an internal combustion engine with a continuously variable transmission (CVT).A promising hybrid scooter powertrain concept allows combining efficiency improvement with additional benefits of electric driving – utilizing a power-split electrified continuously variable transmission (e-CVT) with a planetary gearset. In this hybrid concept, the planetary gearset seamlessly manages the modulation of the transmission ratio interacting with the e-motor’s operation modes. A hybrid strategy, considering the power demand and battery state of charge was developed concurrently with the implementation of all driving modes.The paper explains the e-CVT-layout, the selection criteria of ICE and e-motor-performance, while addressing the applicable hybrid operation modes. The evaluation of performance and efficiency had been conducted in the relevant drive cycle sections.]]></description>
      <pubDate>Tue, 29 Apr 2025 15:53:21 GMT</pubDate>
      <guid>https://trid.trb.org/View/2547847</guid>
    </item>
    <item>
      <title>Trends in the Automated and AutomaticTransmission Systems for Two Wheeled Vehicles</title>
      <link>https://trid.trb.org/View/2547846</link>
      <description><![CDATA[The two-wheeler industry features a diverse range of transmission systems catering to varied riding preferences and market demands. Manual transmissions offer direct gear control, favored by enthusiasts for its precision and customizable performance. Automatic transmissions simplify riding, especially in urban settings, eliminating manual gear shifts and reducing rider fatigue.Understanding the dynamics of transmission systems in the two-wheeler space is crucial for manufacturers, engineers, policymakers, and riders alike. It informs product development, regulatory compliance efforts, and market positioning initiatives in an increasingly competitive and innovation-driven industry landscape.DCT (Dual Clutch Transmission) and manual transmissions represent extremes in rider engagement, automation, and cost. While DCT offers seamless gear changes and convenience at a higher price point, manual transmissions provide direct control and a tactile experience with lower initial costs. Riders weigh these factors when choosing between technological innovation and traditional engagement.Between these two extremes, certain transmissions systems provide manual gear selection with automatic clutch operation, appealing to riders seeking control without the complexities of manual clutch manipulation like the E-Clutch. Continuously Variable Transmission (CVT) systems represent a notable innovation, offering seamless gear ratio adjustments and optimized engine output across riding conditions, enhancing ride quality and rider comfort, particularly in urban environments and have gained a lot of traction in the past decade.Each transmission system presents distinct advantages and challenges, influencing rider preferences and manufacturer strategies. Understanding the dynamics of transmission systems in the two-wheeler space is crucial for manufacturers, engineers, policymakers, and riders alike. It informs product development, regulatory compliance efforts, and market positioning initiatives in an increasingly competitive and innovation-driven industry landscape.The introduction of Semi-Automated Manual Transmission (SMT) stands as a bridge, blending the precision of automated gear shifts with the visceral engagement of manual control.SMT enables clutch less gear shifts, providing riders with a unique synthesis of technological innovation and the hands-on experience enthusiasts cherish. Beyond preserving the art of manual transmission, SMT addresses challenges associated with manual gear changes, mitigating issues like gear grinding and missed shifts. Positioned at the intersection of automated efficiency and the enduring appeal of manual engagement, SMT represents a blend of conventional mechanics and modern-day power electronics.]]></description>
      <pubDate>Tue, 29 Apr 2025 15:53:21 GMT</pubDate>
      <guid>https://trid.trb.org/View/2547846</guid>
    </item>
    <item>
      <title>Analysis of Transmission Efficiency and Transient Dynamics in Rubber V-belt Continuously Variable Transmission</title>
      <link>https://trid.trb.org/View/2535993</link>
      <description><![CDATA[For the purpose of predicting the transmission efficiency during operation of a rubber belt-type CVT for motorcycles, including gear shifting, the authors developed theoretical equations. Conventional studies have often dealt with the theorization of constant speed states, and it has been difficult to predict the transmission efficiency because a theoretical analysis method for the behavior during gear shifting has not been established. The authors compared the results of calculations based on the developed theoretical equations with experimental results, demonstrating their effectiveness.]]></description>
      <pubDate>Mon, 14 Apr 2025 09:35:23 GMT</pubDate>
      <guid>https://trid.trb.org/View/2535993</guid>
    </item>
    <item>
      <title>Evolutionary CVT Metal Belt Further Improves Power Transmission Efficiency</title>
      <link>https://trid.trb.org/View/2529553</link>
      <description><![CDATA[In order to improve the power transmission efficiency of the MID ratio of the evolutionary metal belt, the type of contact between the pulley and the element was changed from linear contact to point contact. It is revealed that the torque transmission efficiency is improved by changes in the torque transmission distribution by the element and the ring.]]></description>
      <pubDate>Wed, 09 Apr 2025 09:52:24 GMT</pubDate>
      <guid>https://trid.trb.org/View/2529553</guid>
    </item>
    <item>
      <title>Vibration Characteristics of Advanced CVT Metal Belts and New Vibration Evaluation Method</title>
      <link>https://trid.trb.org/View/2505974</link>
      <description><![CDATA[Vibration characteristics of a CVT metal belt were evaluated in terms of vibration transmission characteristics of two bearing sections for the DR and DN pulleys. While the resonance phenomena occurred in the inter-axial vibration on conventional belts at 800-840 Hz, they did not occur on the evolutionary type. It was clarified that this resonance phenomena is caused by the additional spin by the spinning motion of the element in the string section.]]></description>
      <pubDate>Tue, 25 Mar 2025 16:57:55 GMT</pubDate>
      <guid>https://trid.trb.org/View/2505974</guid>
    </item>
    <item>
      <title>Design and Analysis of a Novel Super-Fast Multi-Gear Power-Split
          Hybrid Electric Vehicle</title>
      <link>https://trid.trb.org/View/2505934</link>
      <description><![CDATA[Electrified powertrain configurations are critical to the fuel economy and                     performance of hybrid vehicles. While single planetary gear (PG) configurations                     - such as the Toyota Prius - have the advantage of simple control and excellent                     fuel economy, the generator1 is unable to participate in the drive, resulting in                     poor acceleration. To overcome these problems, we propose a new multi-gear                     electronically controlled continuously variable transmission (ECVT) due to its                     high efficiency and excellent acceleration performance. It requires only one PG                     and two synchronizers. For this type of multi-gear ECVT hybrid vehicle, this                     paper describes in detail the synchronizer-based shift logic of the new                     configuration. Furthermore, the power flow and dynamics modeling process in                     different operating modes are systematically analyzed. In addition, the global                     optimal Dynamic Programming (DP) algorithm is presented and a new near-optimal                     energy management strategy, Rapid-DP, is employed to evaluate the acceleration                     and fuel consumption of the new design, respectively. The newly proposed design                     is also qualitatively and quantitatively analyzed under Federal Test Procedure                     72 (FTP72), Highway Fuel Economy Test Cycle (HWFET) and Worldwide Harmonized                     Light Vehicles Test Cycle (WLTC) driving cycles. The case results show that                     compared with the original Toyota Prius, the proposed multi-gear ECVT                     configuration can effectively improve the overall performance, with a fuel                     economy improvement of 4.01%-4.96%, a power improvement of 50% on average, and a                     shift smoothness comparable to that of the Prius under different driving cycles,                     which verifies the validity of the new configuration proposed in this study.                     Meanwhile, this study provides a new theoretical basis for optimizing and                     modifying the technology path of multi-gear power-split hybrid vehicles.]]></description>
      <pubDate>Thu, 06 Feb 2025 15:48:50 GMT</pubDate>
      <guid>https://trid.trb.org/View/2505934</guid>
    </item>
    <item>
      <title>Applying Regular Relief onto Conical Surfaces of Continuously Variable Transmission to Enhance Its Wear Resistance</title>
      <link>https://trid.trb.org/View/2475210</link>
      <description><![CDATA[While investigating the variator transmission of vehicles, the relationship between the technological and service parameters of the working surfaces of conical disks treated by technological methods was established. The service properties are proposed to be enhanced by Regular MicroReliefs (RMRs) created on such surfaces. The optimal technological processing conditions were found, which allow retaining the greatest amount of lubricant. The causes of surface defects, formed on the working surfaces of conical disks of the Continuously Variable Transmission (CVT), are systematized and classified. The wear resistance of such surfaces is proposed to be enhanced by technological methods, in particular, by forming partially RMRs on them. Their application facilitates relaxation processes on the material near to the surface, reduces shear stresses and strains, thus preventing the formation of burrs and extending the life of the conical disks of the CVT. A novel approach for obtaining the toolpaths of the deforming element, based on the so-called “Commis–Voyageur problem” algorithms, is employed in order to research the possibilities for involving that methods in toolpath generation. Dependences between the partial RMR’s formation conditions (deforming forces and feedrate) and microgeometric quality parameters are established. The latter include surface roughness, with a partially RMR applied onto the face surfaces of the test specimen (rotary body). It is found that these microreliefs enhance the ability of oil retaining in plastically deformed traces, formed over the operational surfaces, in comparison with those, that are processed by traditional cutting methods, as turning for example.]]></description>
      <pubDate>Mon, 16 Dec 2024 09:14:53 GMT</pubDate>
      <guid>https://trid.trb.org/View/2475210</guid>
    </item>
    <item>
      <title>Development of a Large Torque Capacity Half-Toroidal CVT</title>
      <link>https://trid.trb.org/View/1787304</link>
      <description><![CDATA[This paper describes a half-toroidal continuously variable transmission (CVT) that has been newly developed. The continuously variable unit (CVU) of this CVT adopts a traction drive as its power transmission principle. The major features of this mechanism include its capacity to transmit large torque, quick ratio changes, and high transmission efficiency in the low torque range. The major CVT performance characteristics and dimensions and features of the various parts of the unit are explained here.]]></description>
      <pubDate>Tue, 03 Dec 2024 17:10:41 GMT</pubDate>
      <guid>https://trid.trb.org/View/1787304</guid>
    </item>
    <item>
      <title>Design principles and traction performance of a novel zero-spin rolling conical traction continuously variable transmission</title>
      <link>https://trid.trb.org/View/2449534</link>
      <description><![CDATA[In the existing traction continuously variable transmission (CVT), half toroidal CVT (HT-CVT) is considered to have a better traction performance. However, the HT-CVT has the spin losses due to its structural limitations, which significantly influences the traction efficiency. In this paper, the kinematic qualities and contact models of a novel zero-spin rolling conical CVT (RC-CVT) are studied, and then the rollers and conical disks are compactly designed through the proposed design principles. Subsequently, the transmission efficiency is investigated by using a detailed numerical model and compared with HT-CVT. Based on these computational models and parameters, the practical spin ratio, spin momentum and traction efficiency of RC-CVT are calculated and compared with HT-CVT. The results show that the practical spin ratio and spin momentum of RC-CVT are much smaller than that of HT-CVT, and the efficiency on fixed transmission ratio is consequently higher than that of HT-CVT.]]></description>
      <pubDate>Fri, 22 Nov 2024 14:31:22 GMT</pubDate>
      <guid>https://trid.trb.org/View/2449534</guid>
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