• Journal of the Korean Society of Mechanical Technology
• /
• v.13 no.2
• /
• pp.45-54
• /
• 2011

A vehicle suspension system performs two functions, the ride quality and the stability, which conflict with each other. Among the various suspension systems, an active suspension system has an external energy source, from which energy is always supplied to the system for continuous control of vehicle motion. In the process of the linearization for the nonlinear active suspension system, the frequency dependent damping method is used for the exact modelling to the real model. The pressure control valve which is controlled by proportional solenoid is the most important component in the active suspension system. The pressure control valve has the dynamic characteristics with 1st order delay. Therefore, It's necessary to adopt the lead compensator to compensate the dynamics of the pressure control valve. The sampling time is also important factor for the control performances. The sampling time value is proposed to satisfy the system performances. After the modelling and simulation for the pressure control valve and vehicle dynamic, the performances of the vehicle ride quality and the stability are enhanced.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.26 no.1
• /
• pp.74-82
• /
• 2002

In this paper the start fuel index was developed to estimate ride quality of a forklift truck during the start motion. Through the consultation with test drivers, definition of start feel was made, and three parameters were selected to describe the start motion. They are engagement shock in the forwarding direction, vertical and pitch vibration respectively. To find out the relation between the measured motion and the subjective fueling, both the subjective rating and the measurement of vehicle motions were performed simultaneously. The correlation analysis between the two kinds of results showed start fuel was expressed by the measured accelerations with accuracy and reliability, Use of the new index has advantages of not only evaluating start fuel only by the measured signals but providing the consistent results which are not affected by physical and mental state of a test driver. Usefulness of the new index was confirmed by verification test on four new forklift trucks of a same model, which showed the order of preference by the index was coincided that by subjective evaluation.

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

• Fashion & Textile Research Journal
• /
• v.19 no.3
• /
• pp.302-311
• /
• 2017

The purpose of this study is to develop an aesthetic and functional bicycle wear for new senior women in their 50s and 60s. We developed bicycle wear that is friendly to bicycling posture and reflects the preference of new senior women. Both the expert group and the subject group evaluated the appearance, completeness of clothing and motion functionality. The results are as followed: First, in the evaluation result of the expert group regarding the appearance and completeness of clothing, high scores are given to design, materials, color scheme, the trends suitability as well as the appearance with regard to clothing fitness. Second, in the results of the evaluation of the appearance and movement functionality targeting the subject groups, movement functionality was rated higher than appearance. In the case of the appearance evaluation, adhesion of both jacket and pants was rated very highly, which is considered to come from the elasticity of the material. In the functionality evaluation, what were pointed out as inconvenient details in the prior studies were found to be all improved and the sleeves and armpit parts were rated highly. Therefore, the pattern design and the usage of the materials suggested in this study were found to be very suitable in the movement on the ride of bicycle.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.16 no.12 s.117
• /
• pp.1231-1237
• /
• 2006

The vibration of a running railway vehicle can be classified on lateral, longitudinal and vertical motions. The important factor on the stability and ride quality of a railway vehicle is the lateral motion. The contact between wheel and rail with conicity influences strongly on the lateral motion. In this study, an experiment for the vibration of a running railway vehicle was performed using a of the scale model of a railway vehicle. Also, the effects on the car-body, bogie and wheelset were examined for the weight and the stiffness of the second suspension system. The experimental results showed that the lateral vibration increases as the wheel conicity and stiffness of the second suspension system increase. And the lateral vibration of the bogie increases as the mass ratio between car-body and bogie increases. Also, the lateral vibration of the wheel becomes high at low speed, while the wheel of 1/20 conicity makes severe vibration at high speed running.

• Proceedings of the KSR Conference
• /
• 2011.10a
• /
• pp.1856-1861
• /
• 2011

As a secondary suspension, the air spring has not good lateral stiffness characteristics. In order to make up for this weak point, lateral damper is used between bogie and carbody. The lateral vibration of carbody can be reduced by the lateral damper. When the damping force of lateral damper becomes worse, the running stability and ride comfort of the railway vehicle go down. Simultaneously the lateral motion of carbody is increased. In this study, the lateral displacement of carbody was studied by the multibody dynamic analysis in accordance with lateral damping force to find the cause of abnormal noise(impact noise) when the vehicle is running. The suitable lateral damping force was reviewed in order not to generate abnormal noise.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2010.10a
• /
• pp.71-76
• /
• 2010

This paper presents the feasibility for improving the ride quality of railway vehicle equipped with semi-active suspension system using magnetorheological(MR) fluid damper. In order to achieve this goal, a fifteen degree of freedom of railway vehicle model, which includes a car body, bogie frame and wheel-set is proposed to represent lateral, yaw and roll motions. The MR damper system is incorporated with the governing equation of motion of the railway vehicle which includes secondary suspension. To illustrate the effectiveness of the controlled MR dampers on railway vehicle secondary suspension system, the sky-hook control law using the velocity feedback is adopted. Computer simulation for performance evaluation is performed using Matlab. Various control performances are demonstrated under external excitation which is the creep force between wheel and rail.

• Transactions of The Korea Fluid Power Systems Society
• /
• v.7 no.3
• /
• pp.20-27
• /
• 2010

A vehicle suspension system performs two functions, the ride quality and the stability, which conflict with each other. An active suspension system has an external energy source, from which energy is always supplied to the system for continuous control of vehicle motion. Therefore, an active suspension system can have even more improved performance. Some control laws have been proposed for active suspension system, but in this paper, an optimal variable structure control(VSC) is proposed. The VSC method is well suited for a class of nonlinear system and can address the robustness issues to constant modelling errors and disturbances. This paper develops an optimal VSC controller and compares its performance to those of a passive suspension system and an active suspension system with an optimal controller. The transient and frequency responses are analyzed respectively.

• Journal of the Korean Society for Railway
• /
• v.9 no.4 s.35
• /
• pp.499-503
• /
• 2006

Maglev vehicles, which are levitated and propelled by electromagnets, often run on elevated flexible guideways comprised of steel, aluminum and concrete. Therefore, an analysis of the dynamic interaction between the Maglev vehicle and the flexible guideway is needed in the design of the critical speed, ride, controller design and weight reduction of the vehicle. This study introduces a dynamic interaction simulation technique that applies structural dynamics. Because the proposed method uses detailed 3D FE models, it is useful to analyze the deformation of the elevated flexible guideway, the dynamic stress, and the motion of the vehicle. By applying the proposed method to an urban transit Maglev vehicle, UTM01, the dynamic response is simulated and validated. From the result of the study, we concluded that the simulation of dynamic interaction between the Maglev vehicle and the flexible guideway is possible and a potential of using computational mechanics.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.17 no.1
• /
• pp.42-47
• /
• 2018

This paper describes the dynamical behavior of the bicycle and its nonlinear effect when magnetic repulsive forces are applied to the bicycle cushion system. A finite-element method was used to obtain its reliabilities by comparing the experimental and numerical values and select the proper magnet sizes. The Equivalent spring stiffness values were evaluated in terms of both linear and nonlinear approximations, where the nonlinear effect was specifically investigated for the ride comfort. The corresponding equations of linear and nonlinear motion were derived for the numerical model with three degrees of freedom. Dynamic behaviors were observed when the bicycle ran over a curvilinear road in the form of a sinusoidal curve. The analysis in this paper for the observed nonlinearity of magnetic repulsive forces will be a useful guide to more accurately predict the cushion design for any vehicle system.