Browsing by Author "Mensur Birhan"

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    Simulation and Control of Wheel Flange Climbing Derailment Using Actuators
    (Addis Ababa University, 2016-11) Mensur Birhan; Zewudu Abadi (PhD); Tolosa Deberie (Mr.) Co-Advisor
    This research explores how active actuation systems can affect rail vehicle dynamics, using a combined multibody simulation and experimental verification strategy. The research addresses an important issue concerning vehicle-track interaction, particularly large vibrations, instabilities in wheel-rail contact forces, and potential derailment, as each of these factors critically impact ride quality, safety operations, and maintenance costs. The methodology contrasts multibody dynamics modeling with experimental validation of key metrics, such as accelerations of the car body and bogie, wheel-rail contact forces, derailment coefficients, wheel lift, attack angles, and spectral vibration characteristics. The simulation-based evaluation compares system performance with and without active control under various operational conditions. The paper will demonstrate the capability of active control to mitigate harmful rail vehicle dynamics. The findings indicate significant improvements across all assessed measures. Active control leads to a 52% improvement in vertical car body acceleration (from 0.076 m/s² to 0.0375 m/s²) and a 35.7% improvement in lateral acceleration (0.28 m/s² to 0.18 m/s²), markedly improving ride comfort and stability. The wheel-rail contact forces are reduced by 1.3% vertically (73.75 kN to 72.8 kN) and laterally 3.6% (8.9 kN to 8.3 kN), which improves wear characteristics and longevity of components. The derailment coefficient is lower by 4.3% (0.115 to 0.11), improving the safety margin, and wheel lift is lower by 2.1% (375×10⁻⁶ m to 367×10⁻⁶ m), facilitating better contact stability. Spectral analysis reveals that active control shifts resonant frequencies down (e.g. from 9.67 Hz to 8.75 Hz) for car body vibrations and simultaneously reduces amplitudes, which signifies that well-targeted vibration suppression is achievable within critical frequency bands. These results give strong support to advance the implementation of active actuation in rail systems, especially in high-speed applications where dynamic performance is important. We showed that active control improves safety, comfort, and maintenance efficiency; furthermore, it also validated both theoretical and experimental models in our study. These results provide a practical basis to use active suspension in future rail vehicles.