• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.336-341
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• 2003

In this paper, resonance durability analysis technique is presented for the fatigue life assessment considering dynamic effect of a vehicle system. In the resonance durability analysis, the frequency response and the dynamic load on frequency domain are used. Multi-body dynamic analysis, finite element analysis, and fatigue life prediction method are applied for the virtual durability assessment. To obtain the frequency response and the dynamic load, the computer simulations running over typical pothole and Belgian road are carried out by utilizing vehicle dynamic model. The durability estimations on the rear suspension system of the passenger car are performed by using the presented technique and compared with the quasi-static durability analysis. The study shows that the fatigue life considering resonant frequency of vehicle system can be effectively estimated in early design stage.

• Proceedings of the KSR Conference
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• 2003.10c
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• pp.455-460
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• 2003

180km/h 급 한국형 틸팅차량의 틸팅 메카니즘 기구동역학 해석을 통하여 얻어진 틸팅 대차를 형성하는 주요 파라메터들의 값을 기반으로 틸팅대차용 엑츄에이터의 성능과 용량을 계산하여 설계에 결과를 반영하고자 한다. 승객의 안락감을 유지하기 위해 차체 틸팅 각가속도에 Sine 연속 함수를 적용하여 차체의 틸팅 제어 패턴을 결정하였으며, 이를 통해 차체의 틸팅 각속도와 틸팅각의 패턴을 얻어내었다. 또한 이번 연구를 통해 틸팅 메카니즘의 파라메타를 변화하면서 각각의 틸팅각에 따른 Swing bar 와 엑츄에이터에 작용되는 반발력에 대한 영향력을 분석, 검토하였으며, 이에 따른 엑츄에이터의 출력과 변위 속도등의 변화를 조사하였다. 이러한 결과와 틸팅 메카니즘 기구동력학 해석의 결과를 토대로 틸팅차량이 요구하는 최적의 틸팅 운동을 수행하는 파라메타를 결정하였다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.4
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• pp.581-587
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• 2013

In a magnetic train set composed of more than two cars, the installation of dampers between cars is carefully considered for improving both the ride quality and the safety, particularly during curve negotiation. In this study, a dynamic simulation of the ride quality and curve negotiation of a Maglev vehicle was carried out. The dynamic model is developed based on multibody dynamics. The presented full vehicle multibody dynamic model integrates the electromagnet model and its control algorithm. By using this model, the effects of the dampers are numerically analyzed. The proposed damper is installed on the vehicle and tested to analyze its effects. In this study, the simulation and measured results of the vehicle behavior and ride quality are discussed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.10
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• pp.967-974
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• 2017

In this paper, a differential-braking-based yaw moment control system was developed to guarantee robust performance against road bank angle. A new target yaw rate model was established by combining the signal from a lateral acceleration sensor and 2-DOF single track model. In addition, a disturbance observer was utilized to take into account parameter uncertainties in yaw dynamics and to improve robust performance of the controller. CARSIM, which is a multi-DOF vehicle dynamic simulation tool, was used to verify the performance of the proposed controller in various driving scenarios. The simulation results indicate that the stability of the vehicle was robustly maintained by the controller, which is characterized by the reflection of the signal of a lateral acceleration sensor signal and by the compensation of the errors in the model parameters via the disturbance observer.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.5
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• pp.541-549
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• 2008

The dynamic contact between a high-speed wheel and an elastic beam is numerically analyzed by solving the whole equations of motion of the wheel and the beam subjected to the contact condition. For the stability of the numerical solution, the velocity and acceleration constraints as well as the displacement constraint are imposed on the contact point. Through the numerical examples, it is shown that the acceleration contact constraint including the Coriolis and centripetal accelerations are crucial for the numerical stability.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.1
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• pp.85-90
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• 2011

To maintain the safety and efficiency of railroad vehicles, it is important to understand the working of the brake system with anti-skid control unit (ASCU) for rolling stocks. In this paper, a HILS (Hardware In-the Loop Simulations) system with ASCU hardware (for logic) and a DSP board (for dynamics) is developed to analyze skidding of the Hanvit-200 train during the process of braking. Experimental results are presented for the case that the skid on one of the four wheels is artificially generated using a Simulink model. A convenient GUI is prepared using ControlDesk of dSPACE.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.383-386
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• 2005

An integrated analytical model which should have essential dynamics on the longitudinal railway vehicle is developed. The model consists of translational movement, rotational movement, brake actuator, adhesion force between rail and wheel, and brake friction force between wheel and pad. Thus, during the deceleration for stopping, a feedback controller controlling the brake cylinder pressure is designed to improve ride quality and to release friction problems. Through the developed model, the feasibility of controlling the cylinder pressure is verified for the better performances during braking.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.1
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• pp.29-35
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• 2002

A simulation program for vehicle dynamic analysis was developed. The Cartesisn coordinate system was used for translational motion and the Euler angle system was used for rotational motion. A three dimensional multi-wheeled vehicle model and equations of motion were derived. Also static equilibrium analysis was added for initial vehicle condition setting. The program user can describe the exact characteristics of suspension spring force and damping force in the user subroutine. A wheel-ground contact model which represents geometrical effect was developed. Two cases of simulation for 16 D.O.F. vehicle model were conducted to validate the developed program by comparing the simulation results with the experimental data.

• Tribology and Lubricants
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• v.34 no.1
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• pp.9-15
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• 2018

Modern high-performance automotive turbochargers (TCs) implement ceramic hybrid angular contact ball bearings in series with squeeze film dampers (SFDs) to enhance transient responses, thereby reducing the overall emission levels. The current study predicts the rotordynamic responses of the commercial automotive TCs (compressor wheel diameter = ~53 mm, turbine wheel diameter = ~43 mm, and shaft diameter at the bearing locations = ~7 mm) supported on ball bearings and SFDs for various design parameters of SFDs, including radial clearance, axial length, lubricant viscosity, and rotor imbalance conditions (i.e., amplitudes and phase angles) while increasing rotor speed up to 150 krpm. This study validates the predictive rotor finite element model against measurements of mass, polar and transverse moments of inertia, and free-free mode natural frequencies and mode shapes. A nonlinear rotordynamic model integrates nonlinear force coefficients of SFDs to calculate the transient responses of the TC rotor-bearing system. The predicted results show that SFD radial clearances, as well as phase angles of rotor imbalances, have the paramount effect on the dynamic responses of TC shaft motions.

• Journal of the Korean Society for Railway
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• v.10 no.5
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• pp.540-545
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• 2007

The tilting train is able to tilt its body towards the center of the turning radius, preventing roll-over of the train as it runs on a curved rail at high-speed. This train, widely accepted for commercial purpose internationally, is very beneficial in that the operating time is shortened without much capital investment to the infrastructure where there are many curved rails. Over several years, the Korea Railroad Research Institute (KRRI) has developed such a train. In this paper, the safety of the Korean tilting train express (TTX) is investigated using a dynamic simulation model. Since proper safety standards have not been established for the TTX, those for the Korean train express (KTX) is employed to analyze the safety and ride comfort of the TTX. This study is useful in predicting the behavior of the TTX and ride comfort, and conforms that designed TTX is stable enough to satisfy the safety standards. It would be useful to recommend proper normal operating speed and determine the maximum safety speed, according to the result. Furthermore, it would be possible to provide basic reference data when analyzing the dynamic effect of the catenary system and the fatigue of the bogie.