• Journal of Korea Game Society
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• v.19 no.3
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• pp.15-24
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• 2019

Many limitations arise when using washout algorithms to calibrate input values in VR content-making environments using VR HMD and motion platforms. Thus, in this study, we designed a new fabrication method using a control object that turns acceleration into a rotational motion. A total of 30 people were tested to see if the improved method was better than the existing one. The results showed significant differences that the improved method is better for realism, immersion and ride comfort.

• The Journal of the Convergence on Culture Technology
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• v.7 no.4
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• pp.801-806
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• 2021

Rail corrugation is continuously increasing due to the lack of maintenance regulations for the amount of rail irregularities. Rail corrugation is causing various problems, such as a decrease in ride comfort and an increase in the amount of track maintenance. In this paper, the effect of rail corrugation on the track force was analyzed by measuring the rail irregularities before and after rail grinding and the track measurements (dynamic wheel load, displacement, and acceleration) for the section where the rail corrugation occurred. In addition, it was experimentally proven that the rail grinding performed to reduce the corrugation of the rail was very effective in reducing the additional forces on the track.

• IEMEK Journal of Embedded Systems and Applications
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• v.17 no.5
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• pp.257-263
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• 2022

Active stabilizers use signals such as steering angle, yaw rate, and lateral acceleration to vary the roll stiffness of the front and rear suspension depending on the vehicle's driving conditions, and are attracting attention as RSC (Roll Stability Control) system that suppresses roll when turning and improves ride comfort when going straight. Various studies have been conducted in relation to active stabilizer bars and RSC systems. However, accurate modeling of passive stabilizer model and active stabilizer model and vehicle dynamics analysis result verification are insufficient, and performance result analysis related to vehicle roll angle estimation and electric motor control is insufficient. Therefore, in this study, an accurate vehicle dynamics model was constructed by measuring the passive/active stabilizer bar model and component parameters. Based on this, the analysis result with high reliability was derived by comparing the roll angle estimation algorithm based on the lateral acceleration and suspension of the vehicle with the actual vehicle driving test result. In addition, it was intended to accurately analyze the motor torque characteristics and roll reduction effects of the electric motor-driven RSC system.

• Smart Structures and Systems
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• v.34 no.2
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• pp.87-96
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• 2024

Smart materials, such as magnetorheological (MR) fluid, have received considerable research attention in recent years due to their unique capabilities. MR fluid, which possesses a magnetic field controllable viscosity, has been extensively studied for vehicular applications with the aim of synthesizing optimal MR fluids, designing optimal MR dampers, and developing control strategies. However, a comprehensive study that primarily focuses on developing a cost-effective semi-active suspension system for a commercial vehicle in a developing nation is still lacking. This study addresses this gap by synthesizing an in-house MR fluid and studying its rheological properties. Subsequently, a novel single-sensor-based controller is developed and closed-loop simulations are conducted on a quarter-car semi-active model. Finally, the overall semi-active quarter-car suspension system is experimentally tested using a suspension test rig. The performance of the proposed system in terms of ride comfort and road holding is evaluated and is compared with simple control strategies. The dynamic range of the developed semi-active MR damper is found to be around 2.3, indicating a significant MR effect. The results suggest an intermediate response using the proposed acceleration-driven controller (ADV) at lower frequencies and similar performance to that of the skyhook controller at higher frequencies. The cost-effective methodology proposed in this study is effective and can be adapted for other semi-active engineering applications.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.9 no.4
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• pp.113-122
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• 2010

Research and development related to advanced railway systems is currently underway presently to promote the maintenance and economic feasibility of subways, and the aim of such research and development is to enhance the functionality, passenger convenience, system safety and reliability assurance of the subway. In this situation, a study that predicts the effect that the development of such an advanced railway system would have on subway users is required. To this end, this study derived willingness to pay and decision factors with the introduction of an advanced railway system after surveying passengers who use subway lines 1~8. The Price Sensitivity Method (PSM) was applied to derive the willingness to pay in relation to user convenience (operating speed, ride comfort, safety, comfort, security and informativeness) with the introduction of an advanced railway system. In addition, willingness to pay and decision factors were examined after explaining the effects of introducing an advanced railway system in detail to subway users. Through the analysis, it was found that willingness to pay amounted to a premium of 148 won ~ 161 won with the introduction of an advanced railway system, and that this was affected by factors such as gender, frequency of use, satisfaction with comfort, and satisfaction with security.

• International Journal of Highway Engineering
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• v.20 no.2
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• pp.35-44
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• 2018

PURPOSES : The purpose of this research is to analyze the characteristics of panels that affect the evaluating results of riding quality and to evaluate the appropriateness of roughness management criteria based on ride comfort satisfaction. METHODS : In order to analyze the influence of panel characteristics of riding quality, 33 panels, consisting of civilians and experts, were selected. Also, considering the roughness distribution of the expressway, 35 sections with MRI ranging from 1.17 m/km to 4.65 m/km were selected. Each panel boarded a passenger car and evaluated the riding quality with grades from 0 to 10, and assessed whether it was satisfied or not. After removing outlier results using a box plot technique, 964 results were analyzed. An ANOVA was conducted to evaluate the effects of panel expertise, age, driving experience, vehicle ownership, and gender on the evaluation results. In addition, by using the receiver operating characteristics (ROC) curve, the MRI value, which can most accurately evaluate the satisfaction with riding quality, was derived. Then, the compatibility of MRI was evaluated using AUC as a criterion to assess whether the riding quality was satisfactory. RESULTS : Only the age of the panel participants were found to have an effect on the riding quality satisfaction. It was found that satisfaction with riding quality and MRI are strongly correlated. The satisfaction rate of roughness management criteria on new (MRI 1.6 m/km) and maintenance (MRI 3.0 m/km) expressways were 95% and 53%, respectively. As a result of evaluating the roughness management criteria by using the ROC curve, it was found that the accuracy of satisfaction was the highest at MRI 3.1-3.2 m/km. In addition, the AUC of the MRI was about 0.8, indicating that the MRI was an appropriate index for evaluating the riding quality satisfaction. CONCLUSIONS : Based on the results, the distribution of the panels' age should be considered when panel rating is conducted. From the results of the ROC curve, MRI of 3.0 m/km, which is a criterion of roughness management on maintenance expressways, is considered as appropriate.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.2090-2100
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• 2011

Railway rail fastening system is the critical device which gives big influences to not only the vehicle driving stability and the orbit's structural stability against the impulsive load, but also the noise vibration and the ride comfort. As a part of the low-carbon green growth, the importance of the railroad industry is getting highlights on its excellent energy-efficiency and eco-friendliness. However, so far the Korea's domestic rail fastening system technology is not so good and the technical reliance to abroad is very heavy. In this study, we conducted comparative analysis on the rail fastening system with new and used one of the same type. And those systems are imported by Seoul Metro and are being used by it. With this basis, we developed the components and the materials and then, established the durability assessment methods appropriate to the Korean domestic circumstances. And through the reliability qualification test on the 7 parts of the rail fastening system, we've improved the reliability and guaranteed the 15 years of service lifetime. ($B_{10}Life15$) Establishment and standardization of Reliability Standard on the parts of the rail fastening system such as anti-vibration pads, guide-plate, screw spike made it possible to perform the internationally fair assessment. And it is thought that we can satisfy the manufactures' and consumers' needs of cost-cutting and qualification security by shortening of assessment period on rail fastening system.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.4
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• pp.683-690
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• 2012

In this work, the semi-active control of a large-sized bus suspension system with an MR damper was studied. An MR damper model that can aptly describe the hysteretic characteristics of an MR damper was adopted. Parameter values of the MR damper model were suitably modified by considering the maximum damping force of a passive damper used in the suspension system of a real large-sized bus. In addition, a fuzzy logic controller was developed for semi-active control of a suspension system with an MR damper. The vertical acceleration at the attachment point of the MR damper and the relative velocity between sprung and unsprung masses were used as input variables, while voltage was used as the output variable. Straight-ahead driving simulations were performed on a road with a random road profile and on a flat road with a bump. In straight-ahead driving simulations, the vertical acceleration and pitch angle were measured to compare the riding performance of a suspension system with a passive damper with that of a suspension with an MR damper. In addition, a single lane change simulation was performed. In the simulation, the lateral acceleration and roll angle were measured in order to compare the handling performance of a suspension system using a passive damper with that of a suspension system using an MR damper.

• International Journal of Automotive Technology
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• v.4 no.4
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• pp.181-191
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• 2003

Since the nonlinearity and uncertainties which inherently exist in vehicle system need to be considered in active suspension control law design, this paper proposes a new control strategy for active vehicle suspension systems by using a combined control scheme, i.e., respectively using a genetic algorithm (GA) based self-tuning PID controller and a fuzzy logic controller in two loops. In the control scheme, the PID controller is used to minimize vehicle body vertical acceleration, the fuzzy logic controller is to minimize pitch acceleration and meanwhile to attenuate vehicle body vertical acceleration further by tuning weighting factors. In order to improve the adaptability to the changes of plant parameters, based on the defined objectives, a genetic algorithm is introduced to tune the parameters of PID controller, the scaling factors, the gain values and the membership functions of fuzzy logic controller on-line. Taking a four degree-of-freedom nonlinear vehicle model as example, the proposed control scheme is applied and the simulations are carried out in different road disturbance input conditions. Simulation results show that the present control scheme is very effective in reducing peak values of vehicle body accelerations, especially within the most sensitive frequency range of human response, and in attenuating the excessive dynamic tire load to enhance road holding performance. The stability and adaptability are also showed even when the system is subject to severe road conditions, such as a pothole, an obstacle or a step input. Compared with conventional passive suspensions and the active vehicle suspension systems by using, e.g., linear fuzzy logic control, the combined PID and fuzzy control without parameters self-tuning, the new proposed control system with GA-based self-learning ability can improve vehicle ride comfort performance significantly and offer better system robustness.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.4
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• pp.353-360
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• 2015

Commercial drivers feel tired more than the general public, because their driving times are long and they experience more idle vibration. In this study, we developed a nonlinear model of a magnetic, linear spring seat suspension to determine the optimal design to improve ride comfort. The resonant frequency for the optimal design of the suspension was found to be 3.5 Hz, and the stiffness was analyzed through displacement-load experiments. Additionally, the vibration transmissibility was analyzed by the suspension stiffness, and the existing coil spring type vibration transmissibility was found to be 0.99. A parallelogram type magnetic spring was determined to result in a better performance than the existing spring with a vibration transmissibility of 0.823.