• Journal of the Korean Society for Railway
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• v.10 no.4
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• pp.444-450
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• 2007

The bi-modal tram guided by the magnetic guidance system has two car-bodies and three axles. Each axle of the vehicle has an independent suspension to lower the floor of the car and improve ride quality. The turning radius of the vehicle may increase as a consequence of the long wheel base. Therefore, the vehicle is equipped with the All-Wheel-Steering(AWS) system for safe driving on a curved road. Front and rear axles should be steered in opposite directions, which means a negative mode, to minimize the turning radius. On the other hand, they also should be steered in the same direction, which means a positive mode, for the stopping mode. Moreover, only the front axle is steered for stability of the vehicle upon high-speed driving. In summary, steering angles and directions of the each axle should be changed according to the driving environment and steering mode. This paper proposes an appropriate AWS control algorithm for stable driving of the bi-modal tram. Furthermore, a multi-body model of the vehicle is simulated to verify the suitability of the algorithm. This model can also analyze the different dynamic characteristics between 2WS and AWS.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.4
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• pp.19-29
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• 1995

This paper discusses the stick-slip phenomenon of the driveline system of a vehicle in consideration of friction. Friction is operated on the between of flywheel and clutch disk. The expressions for obtaining the results have been derived from the equation of motion of a three degree of freedom frictional torsion vibration system which is made up driving part(engine, flywheel), driven part(clutch, transmission) and dynamic load part(vehicle body) by applying forth-order Rungekutta method. It was found that the great affect parameters of the stick-slip or stick motion were surface pressure force between flywheel and clutch disk, time decay parameter of surface pressure force and 1st torsional spring constant of clutch disk when driveline system had been affected by friction force. The results of this study can be used as basic design data of the clutch system for the ride quality improvement of a car.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.46-55
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• 2008

Maglev is a system that a train runs levitated above a rail. Therefore it is very important to maintain a constant levitation gap for achieving serviceability and ride comfort. This study is a cooperation research subject of the 3-1 subject, performance improvement of maglev track structures, of the Center for Urban Maglev Program in Korea, started in 2006. The aim of this study is development of rapid constructions of bridge superstructure for maglev. At present, precast deck is widely used because of its superiority to cast-in-place concrete on quality and the term of works. The research group suggested basic systems of maglev guideway with PSC-U type and trapezoidal open steel box type girder, and precast deck, cooperating with Korea Railroad Research Institute, the managing institute of the 3-1 subject. In this study, longitudinally full-scale guideway girder system was fabricated and static/dynamic test of the girder was performed for the purpose of the performance evaluation.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.2
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• pp.123-130
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• 2004

The automobile suspension system is composed of parts that affect performances of a vehicle such as ride quality, handling characteristics, straight performance and steering effort, etc. Moreover, by using the finite element analysis the cost for the initial design step can be decreased. In the design of a suspension system, usually system vibration and structural rigidity must be considered simultaneously to satisfy dynamic and static requirements simultaneously. In this paper, we consider the weight reduction and the increase of the first eigen-frequency of a suspension part, the upper control arm, especially using topology optimization and size optimization. Firstly, we obtain the initial design to maximize the first eigen-frequency using topology optimization. Then, we apply the multi-objective parameter optimization method to satisfy both the weight reduction and the increase of the first eigen-frequency. The design variables are varying during the optimization process for the multi-objective. Therefore, we can obtain the deterministic values of the design variables not only to satisfy the terms of variation limits but also to optimize the two design objectives at the same time. Finally, we have executed reliability based optimal design on the upper control arm using the Monte-Carlo method with importance sampling method for the optimal design result with 98％ reliability.

• Structural Engineering and Mechanics
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• v.68 no.4
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• pp.459-473
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• 2018

Temperature fields and temperature deformations induced by time-varying solar radiation, shadow, and heat exchange are of great importance for the ride safety and quality of the maglev system. Accurate evaluations of their effects on the dynamic performances are necessary to avoid unexpected loss of service performance. This paper presents a numerical approach to determine temperature effects on the maglev train/guideway interaction system. Heat flux density and heat transfer coefficient of different components of a 25 m simply supported concrete guideway on Shanghai High-speed Maglev Commercial Operation Line is calculated, and an appropriate section mesh is used to consider the time-varying shadow on guideway surfaces. Based on the heat-stress coupled technology, temperature distributions and deformation fields of the guideway are then computed via Finite Element method. Combining guideway irregularities and thermal deformations as the external excitations, a numerical maglev train/guideway interaction model is proposed to analyze the temperature effect. The responses comparison including and excluding temperature effect indicates that the temperature deformation plays an important role in amplifying the response of a running maglev, and the parameter analysis results suggest that climatic and environmental factors significantly affect the temperature effects on the coupled maglev system.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.1303-1308
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• 2011

In the modern society various types of transportation mode are utilized, among them the subway system is the one of the main transportation mode which more than 7.21 million people ride a day. Because of interests on the indoor air quality (IAQ) of underground public facilities, concerns on IAQ of subway system by many people are increasing. There are several approach to improve IAQ of subway station, such as installing platform screen door (PSD), frequent tunnel washing-out, and etc, however there has not been any attempt to improve IAQ of subway cabin inside. Most technologies for removing airborne particulate matters are known to be difficult to adopt on the subway cabin since the problem of maintenance cost. Therefore, the ultimate object of this study is a practical development of cabin air cleaning system which can reduce the concentration of airborne particles and harmful gases at the same time. The subway cabin air purifier (SCAP) was developed for removing particulate matters and gases pollutants inside a cabin. The whole system was designed and the roll-filter device was manufactured based on numerical prediction results. It is expected that SCAP could reduce indoor air pollutants in the subway cabin practically and it can be applied to other part of transportation vehicles.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.6
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• pp.573-578
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• 2013

In the case of the Back EMF voltage contains the harmonics, the motor torque ripple and vibration is occurred by the current pulsation, because IPMSM control algorithm is the model which is assumed that it contains a sinusoidal Back EMF voltage. To improve ride quality, in the case of IPMSM for EV, improving the torque control characteristics is necessary. Therefore, there is a need to minimize the influence of the harmonics. In this paper, the investigation to decrease the current distortion factor has been performed for improving torque control characteristics by applying the non-sinusoidal Back EMF to IPMSM model.

• Transactions of The Korea Fluid Power Systems Society
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• v.7 no.4
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• pp.32-38
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• 2010

A semi-active suspension is an automotive technology that controls the vertical movement of the vehicle while the car is driving. The system therefore virtually eliminates body roll and pitch variation in many driving situations including cornering, accelerating, and braking. This technology allows car manufacturers to achieve a higher degree of both ride quality and car handling by keeping the tires perpendicular to the road in corners, allowing for much higher levels of grip and control. An onboard computer detects body movement from sensors located throughout the vehicle and, using data calculated by opportune control techniques, controls the action of the suspension. Semi-active systems can change the viscous damping coefficient of the shock absorber, and do not add energy to the suspension system. Though limited in their intervention (for example, the control force can never have different direction than that of the current speed of the suspension), semi-active suspensions are less expensive to design and consume far less energy. In recent time, the research in semi-active suspensions has continued to advance with respect to their capabilities, narrowing the gap between semi-active and fully active suspension systems. In this paper we are studied the characteristics of vehicle movement during the field test with conventional and semi-active suspension system.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.2
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• pp.129-143
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• 1998

The vibrations of steering wheel are required to be reduced for convenient ride quality and good controllability. This phenomenon, vibration of steering wheel, is occured by interaction with suspension system, steering system, vehicle body, engine/transmission and tire complicately. But reviewing the current research activities, most researches are performed for the vibration analysis of steering wheel with a simple model, and mot easy to be applied to the variation of each component element connected with steering system as well as that of the steering system. In this study, suspension system and steering system are modelled by the T.L.H. coordinate system which is usually used by a passenger car maker. Also, rigid body motions of engine and elastic motions of vehicle body in the previous study are considered. Derive the equation of motion in 29 d.o.f. and the vibration of steering wheel is analyzed numerically and verify the midelling of steering system by comparison with test results for real car. And then, the optimal design values of the engine mount system obtained from the previous study are applied to the verified steering system model and investigate the effects of various engine mount design values on the vibration of steering wheel.

• Journal of Institute of Control, Robotics and Systems
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• v.7 no.3
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• pp.209-217
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• 2001

In this paper, we propose a linear quadratic regulator(LQR) controller design for the active suspension using evolution strategy(ES) and neural network. We can improve the inherent suspension problem, the trade-off between ride quality and suspension travel by selecting appropriate weight in the LQR-objective function. Since any definite rules for selecting weights do not exist, we replace the designers trial-and-error method with ES that is an optimization algorithm. Using the ES, we can find the proper control gains for selected frequencies, which have major effects on the vibrations of the vehicle. The relationship between the frequencies and proper control gains are generalized by use of the neural networks. When the vehicle is driven, the trained neural network is activated and provides the proper gains for operating frequencies. And we adopted double sky-hook control to protect car component when passing large bump. Effectiveness of our design has been shown compared to the conventional sky-hook controller through simulation studies.