• Proceedings of the KSR Conference
• /
• 2009.05a
• /
• pp.1431-1440
• /
• 2009

A subway in Seoul has had a major role of public transportation after the opening of Seoul Subway Line 1 on August 15, 1974 and it has reached 34.7% of the transportation of Seoul citizens. The extended length of the subway system suppled with DC power in Korea is about 500km. In this system, the devices which are proper for regenerative power system are being required because of changeover from old braking and ATS signal system to regenerative braking and ATO signal system. In this paper, we reviewed the safety standards for the insulated hangers in overhead contact line. These hangers which have depended on foreign imports are being developed in Korea considering ease of demand and supply and economic effects.

• Proceedings of the KSR Conference
• /
• 2009.05b
• /
• pp.595-600
• /
• 2009

Passengers in a vehicle feel uncomfortable due to squeal noise. Squeal noise, a kind of self-excited vibration, is generated by the friction force between the disc and the pad of the automobile. In this paper, modal analysis of wheel brake system was performed in order to prediction of squeal phenomenon. It was shown that the prediction of system instability is possible by FEM. Finite element model of that brake system was made. Some parts of a real brake was selected and modeled. The normal mode analysis method performs analyses of each brake system component. Experiment of modal analysis was performed for each brake components and experimental results were compared with analytical result from FEM. The complex eigenvalue analysis results compared with braking test. The analysis results show good correlation with braking test for the squeal frequency at an unstable mode.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.4 no.6
• /
• pp.223-228
• /
• 1996

The frequency of the brake squeal noise can be changed during braking, and this frequency shifting is due to variation of braking deceleration rate. The natural frequency of the brake system also shifted according to deceleration rate. It makes difficult to treat this problem. This paper shows an experimental study on the brake squeal noise having main frequencies of about 450~500Hz. And it shows how to improve the brake squeal noise problem.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.36 no.12
• /
• pp.868-873
• /
• 1987

In this pater, we have proposed a synthetic main chopper circuit for the chopper controlled electric automobile. The proposed chopper circuit operates as a step-down chopper in powering mode and as a polarity reversion type chopper in regenerative braking mode. In this study, it was found that powering and regenerative braking operations using the separately excited D.C motor can be controlled continuously only by gate signals of the chopper without changing the connection of the circuit.

• Proceedings of the KSR Conference
• /
• 2002.05a
• /
• pp.411-416
• /
• 2002

The strength evaluation of a wheel is becoming very important due to the high speed of railway system and the reduction of wheel weight. Therefore, in this study, the influence of thermal stress at tread breaking in Korean High Speed Train wheel was investigated using FEM. During FEM analysis, the mechanical load or wheel-rail contract load and braking load were considered. When 300% of the block force was applied, the maximum von Mises stress of 61.0 ㎫ was found at the outside plate around 400mm far away from the wheel center.

• Journal of the Korean Society for Precision Engineering
• /
• v.20 no.3
• /
• pp.58-65
• /
• 2003

Vehicle acceleration data from an accelerometer and wheel speed data from standard, 50-tooth antilock braking system wheel speed sensors are used to estimate the absolute longitudinal speed of a vehicle. We develop the four velocity estimation algorithms. And we compare experimental results with the Butterworth filtered speed from the fifth wheel and find that it is possible to estimate absolute longitudinal vehicle speed during a hard braking maneuver lasting three seconds.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.9
• /
• pp.493-501
• /
• 2016

In this study, core technologies of a traction system on a mountain tram operating on the track of mountain road full of sharp curves and steep gradients were developed. In domestic mountain resort areas, sometimes the transportation service is not provided in winter because of ice and heavy snow on roads, so a mountain railway service independent of the climate and geographic conditions is needed. A traction system was designed taking into account of the power of a traction motor to climb the gradient of 120 ‰, which is common in domestic mountainous areas. and power transmission system was designed to consider the installation space for the traction system. In addition, a reduction gear and a propeller shaft were developed. An elastic pinion was developed and applied to the rack & pinion bogie system for steep gradient so that noise and vibration generated by contact between the steel gears could be reduced. Impact comparison tests showed that the vibration level of the elastic pinion is one-third lower than that of previous steel pinion. Independent rotating wheels and axles were developed for the bogie system to operate on the sharp curve of a 10 meter radius. In addition, the band braking system was developed to enhance the braking force during running on the steep gradient. A test for the braking force showed it exerts the required braking force. The performance of the developed core components were verified by the tests and finally they were applied to the bogie system running on the track of steep gradient and sharp curve.

• Journal of the Ergonomics Society of Korea
• /
• v.35 no.1
• /
• pp.11-27
• /
• 2016

Objective: The purpose of this study was to develop and evaluate high technology adaptive driving controls, such as mini steering wheel-lever system and joystick system, for the people with physical disabilities in the driving simulator. Background: The drivers with severe physical disabilities have problems in operation of the motor vehicle because of reduced muscle strength and limited range of motion. Therefore, if the remote control system with driver-by-wire technology is used for adaptive driving controls for people with physical limitations, the disabled people can improve their quality of life by driving a motor vehicle. Method: We developed the remotely controlled driving simulator with drive-by-wire technology, e.g., mini steering wheel-lever system and joystick system, in order to evaluate driving performance in a safe environment for people with severe physical disabilities. STISim Drive 3 software was used for driving test and the customized Labview program was used in order to control the servomotors and the adaptive driving devices. Thirty subjects participated in the study to evaluate driving performance associated with three different driving controls: conventional driving control, mini steering wheel-lever controls and joystick controls. We analyzed the driving performance in three different courses: straight lane course for acceleration and braking performance, a curved course for steering performance, and intersections for coupled performance. Results: The mini steering wheel-lever system and joystick system developed in this study showed no significant statistical difference (p>0.05) compared to the conventional driving system in the acceleration performance (specified speed travel time, average speed when passing on the right), steering performance (lane departure at the slow curved road, high-speed curved road and the intersection), and braking performance (brake reaction time). However, conventional driving system showed significant statistical difference (p<0.05) compared to the mini steering wheel-lever system or joystick system in the heading angle of the vehicle at the completion point of intersection and the passing speed of the vehicle at left turning. Characteristics of the subjects were found to give a significant effect (p<0.05) on the driving performance, except for the braking reaction time (p>0.05). The subjects with physical disabilities showed a tendency of relatively slow acceleration (p<0.05) at the straight lane course and intersection. The steering performance and braking performance were confirmed that there was no statistically significant difference (p>0.05) according to the characteristics of the subjects. Conclusion: The driving performance with mini steering wheel-lever system and joystick control system showed no significant statistical difference compared to conventional system in the driving simulator. Application: This study can be used to design primary controls with driver-by-wire technology for adaptive vehicle and to improve their community mobility for people with severe physical disabilities.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.6 no.5
• /
• pp.222-227
• /
• 1998

Collision warning systems have been an active research and development area as the interests and demands for ASV's (Advanced Safety Vehicles) have increased. This paper presents an experimental investigation of a collision warning system for automobiles. A collision warning HiLS(Hardware-in-the-Loop Simulation) system has been designed and used to test the collision warning algorithm, radar sensors, and warning displays under realistic operating conditions in the laboratory. the collision warning algorithm is operated by a warning index, which is a function of the warning distance and the braking distance. The computer calculates velocities of the preceding vehicle and following vehicle, relative distance and relative velocity of the vehicles using vehicle simulation models. The relative distance and the relative velocity are applied to the vehicle simulator controlled by a DC motor.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1997.10a
• /
• pp.605-608
• /
• 1997

In this paper, the case study of reducing rotational errors is done for a grinding spindle with an active magnetic bearing system. The rotational errors acting on the magnetic bearing spindle are due to mass unbalance of rotor, runout, grinding excitation and ed nonlinear dynamics of electromagnets. For the most case, the electrical runout of sensor target is big even in well-finished surface; this runout can cause a rotation error amplified by feedback control system. The adaptive feedforward method based on LMS algorithm is discussed to compensate this kind of runout effects, and investigated its effectiveness by numerical simulation and experimental analysis. The rotor orbit size in both bearings is reduced about to 5 pin due to lX rejection by feedforward control up to 50,000 rpm.