• 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.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.6
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• pp.17-22
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• 2003

An airship is statically unstable, because it has no wing, relatively small tails and a large hull. Hence, an accurate prediction of dynamic stability is critical. In this study, dynamic stability data of the 50m Length Airship were acquired through forced oscillation wind tunnel tests. The tests were done in Birhle Applied Research Inc's Lange Amplitude Multi-Purpose(BAR LAMP) Facility located in Germany. The tests were composed with 16 static runs and 26 dynamic runs. As results, it is obtained that dynamic characteristics of the airship depend on the sideslip angle, the angular rate and its direction as well as the angle of attack. Generally, three directional moments have damping, but the normal force, the side force, and the cross-derivatives are unstable. The dynamic derivatives are not sensitive to the control surfaces, but nonlinear to the sideslip angle.

• Journal of Korean Society of Transportation
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• v.35 no.2
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• pp.129-142
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• 2017

Accident Black Spot Improvement Project is the representative road safety intervention to eliminate environmental risk factors on the roadway by installing road safety facilities. Although it is one of the main road safety projects in Korea, there has been a lack of effort analyzing the traffic accident reduction effects of this project. In this study, therefore, we selected 4,171 road black spots from 2004 to 2013 and investigated the traffic accident reduction effects of 5 road safety facilities by using "Comparison Group(C-G)" method. Through the analysis, it was found that the number of traffic accidents were lowered by 4.45% with traffic islands, 32.17% with road paved markers, and 24.13% with speed cameras, respectively. However, 0.61% with pedestrian fencing and 1.67% with skid resistant pavement were increased on the other hand. In addition, we also analyzed traffic accident reduction facilities' performance on specific types of collision mentioned in manual on road safety facilities by Ministry of Land, Infrastructure and Transport. It was shown that the number of bad weather traffic accidents were reduced by 52.96% with road paved markers, pedestrians accidents were reduced by 62.77% with pedestrian fencing and rear-end collisions were reduced by 26.00% with skid resistant pavement.

• Journal of the Korean Society of Safety
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• v.12 no.4
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• pp.214-219
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• 1997

The mechanical seals, which are installed in rotating machines like pump and compressor, are generally used as sealing devices in the many fields of industries. The failure of mechanical seals such as leakage, crack, breakage, fast and severe wear, excessive torque, and squeaking results in big problems. To identify abnormal phenomena on mechanical seals and to propose the proper monitoring parameter for the failure of mechanical seals, sliding wear experiments were conducted. Acoustic emission, torque, and temperature were measured during experiments. Optical microstructure was observed for the wear processing after every 10 minute sliding at rotation speed of 1750 rpm and scanning electron microscopy was also observed. Except for the initial part of every experiment, the variation of acoustic emission was well coincided with torque variation during the experiments. This study concludes that acoustic emission and torque are proper monitoring parameters for the failure of mechanical seals. The intensity of acoustic emission signals is measured in root mean square voltage. Temperature of sealing face will be used as a parallel parameter for increasing the reliability of monitoring system.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.6
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• pp.895-906
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• 2018

The improvement project for school zone in Korea is occurring mostly in kindergartens and elementary schools in which children are mainly active, and is being promoted as part of measures to prevent children's traffic accidents. However, since the study on the essential installation facilities and proper level of safety facilities for School zone is lacking, this study relatively evaluated the efficiency of safety facility installation using DEA (Data Envelope Analysis) and suggested improvement plan. We built the facilities and incident data for 28 school zones in Hwaseong City. Six major facilities (Raised intersection, Raised crosswalk, Protective fence, Skid Proof, Speed hump, Speed cameras) that have proven to be effective in the preceding research were analyzed as input factors. As a result of the analysis, only 12 out of 28 showed efficiency and 16 out of efficiency. Effective groups of school zones were found to have fewer installed Protective fences, Skid Proof, and Speed cameras installations than school zones classified as ineffective groups. Protective fences were found to be efficient even if only 47% of the total extension of the school zone was installed, and the number of slip prevention facilities was 8.7 per square km. The number of subjects to be compared is 28, so this study is limited to use as a relative efficiency evaluation index, and it can be grouped into nationwide units and efficiency evaluation can be done for each group.

• Journal of the Korea Institute of Military Science and Technology
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• v.5 no.3
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• pp.77-86
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• 2002

An experimental study of the vortex interaction characteristics of a delta wing/LEX configuration was conducted in a wind tunnel using the micro water droplet and laser beam sheet visualization technique. The main focus of this study was to analyze the effect of the angle of attack and sideslip angle on the vortex interaction and vortex breakdown. These tests were accomplished at angles of attack between $16^{\circ}$ and $28^{\circ}$ and sideslip angle between $0^{\circ}$ and $-15^{\circ}$ at free-stream velocity of 6.2 m/s. Flow visualization data provide a description of the vortex interaction between LEX and wing vortices, and of the vortex breakdown. The introduction of LEX vortex stabilized the vortical flow, and delayed the vortex breakdown up to higher angle of attack. The vortex interaction and breakdown was promoted on the windward side, whereas they are suppressed on the leeward side.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.2
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• pp.209-220
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• 1996

In this paper, dynamic performance of 4WD/4WS Electric-driven vehicles is investigated. A coupled dynamic model is introduced for longitudinal, lateral and yawing motion of 4WD/4WS vehicles. Based on the coupled model, dynamic performance is analyzed for steady-state steering, acceleration steering and brake steering, respectively. These non steady-state cornering analysis is important for non-paved road maneuvering, trajectory projection for armored vehicle and future AVCS(Advanced Vehicle Control System) technology. Simulation results are obtained based on a simulink module for the introduced model.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.6
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• pp.1402-1406
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• 2005

A study on the vehicle stability is discussed. In the field of the studies the electronic control systems help overcoming the limit of improvement in vehicle performance with the methods above. Driving stability is mainly incorporated with the later motion of a vehicle generated by the driver's steering input. Recently VDC system has been studieed in order to improve the active stability. This VDC system uses the active braking force. This paper propose the ATC that uses driving force. This paper compared VDC with ATC through an experiment.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.2
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• pp.110-116
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• 2011

The current study investigated the friction property of angle and width effect for micro-scale grooved crosshatch pattern on SKD11 steel surface against bearing steel using pin-on-disk type. The samples fabricated by photolithography process and then these are carry out the electrochemical etching process. We discuss the friction property due to the influence of a hatched-angle and a width of groove on contact surface. We could be explained the lubrication mechanism for a Stribeck curve. So It was found that the friction coefficient depend on an angle of the crosshatch on contact surface. It was thus verified that micro-scale crosshatch grooved pattern could affect the friction reduction. Also, it is play an important a width of groove to be improved the friction property. I was found that friction property has a relationship between a width and an angle for micro-grooved pattern.

• Journal of Korean Ophthalmic Optics Society
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• v.10 no.4
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• pp.273-281
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• 2005

The weight of spectacles fined on is resolved into its components along the nose's slide plane and the normal to the nose plane where the nosepad is located. The equation and its numerical solution to determine the component force was derived as a function of splay angle ${\Psi}$, $sin{\Psi}$, $cos{\Psi}$, and $cot{\Psi}$, incorporated with ${\theta}$ and ${\Phi}$, the angles viewed from side and front of the face, respectively. Values of inclination angle ${\theta}$ and ${\Phi}$ could be obtained to fulfill the condition where the frictional force between the nose and pad is either greater than the normal pressure exerted by the spectacles on the nose. With the value of ${\theta}$ fixed the normal pressure increases as ${\Phi}$ increases. With ${\Phi}$ fixed, the effect of ${\theta}$ is the same.