• 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.10 no.6
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• pp.234-240
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• 2002

This paper treats the problem of estimating the longitudinal velocity of a braking vehicle using measurements from an accelerometer and wheel speed data from standard anti-lock braking wheel speed sensors. We develop and experimentally test three velocity estimation algorithms of increasing complexity. The algorithm that works the best gives peak errors of less than 3 percent even when the accelerometer signal is significantly biased.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1326-1330
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• 2008

The failure mode of steel road wheels in a vehicle is cracks from ventilation hole through to contact plane on steel wheel's disc plate. But a number of cracks of Cornering Fatigue Limit Test is on contact plane near to wheel nut mounting area, even though it's satisfied with specified cycles. So this paper searches out causes to improve durability and reliability of C.F.T by uni-axial bending moment test. The verified cause is a "fretting" on contact area of steel wheel. In result, this paper suggests a solution to prevent a fretting by inserting a damping shim, 0.7mm between steel wheel contact areas. Therefore this paper makes it possible to move crack position of C.F.T in steel wheel from contact plane to vehicle's failure mode.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.606-612
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• 2008

Creep force is one of the only appeared at conventional train which used to be driven by metallic wheel and rail contact. Due to the elastic deformation of wheel/rail contact patch by the weights of wheel and all the components related to it, creep force generates and becomes to the decision factor of critical speed of bogie(or railway vehicle) which is the criteria of avoiding vehicle to be unstable. There are many kind of factors which affect generation of creep force at a wheel/rail contact surface such as viscosity of contact patch, velocity, wheel and rail geometric profile, mechanical properties of wheel and rail. This paper concentrates on a wheelset simple 2 DOF Equation of Motion being exerted. From the simple numerical analysis using linear solution about getting creep force some factors could find roughly. Among the factors geometric parameter could be the one of most important for this study. In the future we'll prolong the range of study to find out method of measuring creep force easily.

• Structural Engineering and Mechanics
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• v.69 no.5
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• pp.499-509
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• 2019

While the wheel flat is an asymmetrical phenomenon in the railway, majority of researches have used two-dimensional models in the investigation of the effect of wheel flat on the wheel rail forces. This is due to the considerably low computational costs of two dimensional (2D) models although their reliability is questionable. This leaves us with the question of "what is the optimum modeling technique?". It is addressed in this research. For this purpose, two and three dimensional numerical models of railway vehicle/track interaction were developed. The three dimensional (3D) model was validated by comparisons of its results with those obtained from a comprehensive field tests carried out in this research and then, the results obtained from the 2D and 3D models were compared. The results obtained indicate that there are considerable differences between wheel/rail forces obtained from the 2D and 3D models in the conditions of medium to large wheel-flats. On the other hand, it was shown that the results of the 2D models are reliable for particular ranges of vehicle speed, railway track stiffness and wheel-fats lengths and depths. The results were used to draw a diagram, which presents the optimum modeling technique, compromising between the costs and accuracy of the obtained results.

• International Journal of Automotive Technology
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• v.7 no.7
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• pp.803-812
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• 2006

In order to reduce the negative effects of dynamic coupling among vehicle subsystems and improve the handling performance of vehicle under severe driving conditions, a vehicle chassis control integration approach based on a main-loop and servo-loop structure is proposed. In the main-loop, in order to achieve satisfactory longitudinal, lateral and yaw response, a sliding mode controller is used to calculate the desired longitudinal, lateral forces and yaw moment of the vehicle; and in the servo-loop, a nonlinear optimizing method is adopted to compute the optimal control inputs, i.e. wheel control torques and active steering angles, and thus distributes the forces and moment to four tire/road contact patches. Simulation results indicate that significant improvement in vehicle handling and stability can be expected from the proposed chassis control integration.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.6
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• pp.600-606
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• 2012

Upon investigation of the damaged wheels for high speed train it was determined that the damage was caused by rolling contact fatigue during operation of train. The major problems that railway vehicle system using wheel-rail has to face during operation of railway vehicle are rolling contact fatigue, cracks in wheels, cracks in rails and wheel-rail profile wear. If these deficiencies are not controlled at early stages the huge economical problems due to unexpected maintenance cost in railway vehicle can be happened. Also, If the accurate knowledge of contact conditions between wheel and rail can be evaluated, the damage of wheel can be prevented and the maintenance operation can save money. This paper presents the applicability of electro-magnetic technique to the detection and sizing of defects in wheel. Under the condition of continuous rolling contact fatigue the damage of wheel has continuously monitored using the applied sensor. It was shown that the usefulness of the applied sensor was verified by twin disc test and the measured damaged sizes showed good agreement with the damaged sizes estimated by electro-magnetic technique.

• Journal of the Korean Society for Railway
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• v.12 no.2
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• pp.230-235
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• 2009

We have conducted an experimental study to analyze characteristics of the wheel profile wear and an influence of the wheel flange wear on the vehicle's vibration characteristics. In experiment with EMU, wheel profile wear is severe at the beginning of the commercial operation. In this stage, the variations of the wheel dimension parameters and equivalent conicity is changed rapidly. Along with a mileage of the test vehicle, the wear of the wheel flange is increased and also the vibration level of the car-body is increased. The peak-peak mean value of the body vibration is estimated as good level, but the level is approached at the limit of the good level as mileage increases. Especially, the peak-peak maximum value of the body vibration shows the distinct increase of vibration level.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.23 no.6 s.165
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• pp.931-942
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• 1999

This paper develops a 3 DOF vehicle model which includes lateral, roll and yaw motion to study a 4WS vehicle. The model is used for the simulation of a 4WS vehicle behavior, and to derive a control algorithm for rear wheel steering. This paper uses a feedforward plus feedback control scheme to compute a rear wheel steering angle. The feedforward control scheme for computing the first rear wheel steering angle uses a gain which is acquired by multiplying a proper value on a gain to maintain a zero sideslip angle. The feedback control scheme for computing the second rear wheel steering angle uses fuzzy logic and model following control scheme. A linear 2 DOF model is used as a reference model for model following control, and is derived from the developed 3 DOF model by neglecting sprung mass roll motion. A reference state variable is yaw rate, and is computed using the linear 2 DOF model. J-turn and lane change maneuver simulation are performed to show the effectiveness of the developed control scheme. The simulation results show that the 4WS vehicle with the developed control scheme has much better performance in yaw rate, lateral acceleration, roll angle, and sideslip angle than the 2WS vehicle. Also, the results show that the performance of the developed control is close to the one of an optimal control which assumes all states are perfect.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.1922-1928
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• 2011

The rail inclination produces a wider bearing area between the wheel and the rail by moving the wheel rail contact area away from the gauge towards the centre of the railhead, thus improving the wear pattern of the railhead and wheel treads. It is essential to keep the rail inclination within the allowable range to ensure optimum track geometry. Neglecting the rail inclination geometrical parameters in a track quality evaluation can cause safety of railway vehicle and serviceability problems. In this paper, we examined the effect of the rail inclination in general geometry state of the railway track using VI-Rail and analyzed running safety when the railway vehicle passing through curves depending on change of the rail inclination and running speed.