• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.2
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• pp.130-136
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• 2001

This paper presents an of a brake pressure restriction valve to a motorcycle anti-lock brake system(ABS). In the conventional anti-lock brake system of automobiles, slip ratio as a control variable is actively controlled, which requires wheel speed sensors, ECU, and a pressure modulator. In the ABS valve that has been developed for use in motorcycles, however, the brake pressure that is close to the wheel locking pressure is preset by simple exercises and then the valve just allows to pass the wheel locking pressure and cutoff the remaining pressure. Simulation studies with a single wheel braking dynamics and lumped chassis model show that the pressure restriction valve has basic ABS functions as well as some robustness properties for the uncertain load and road conditions as well as various initial braking speeds. Field tests also show that the pressure restriction valve avoids the wheel locking effectively.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.2
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• pp.217-223
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• 2003

The power steering system has been adopted in most vehicle system for an easy maneuverability. In this paper, a hydraulic power steering(HPS) model for the computer simulation is developed and used to power steering simulation. The simulation shows that the steering wheel torque with HPS model is less than that without HPS model. In addition, the shimmy vibration at the steering wheel is also simulated and compared to the test data. The lateral displacement of the steering wheel is calculated by imposing the lateral acceleration of the knuckle as a vibration input. The frequency response of the steering wheel is in a good agreement to the test data.

• International Journal of Control, Automation, and Systems
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• v.2 no.4
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• pp.485-493
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• 2004

Open-loop position estimation methods are commonly used in mobile robot applications. Their strength lies in the speed and simplicity with which an estimated position is determined. However, these methods can lead to inaccurate or unreliable estimates. Two position estimation methods are developed in this paper, one using a single optical flow sensor and a second using two optical sensors. The first method can accurately estimate position under ideal conditions and also when wheel slip perpendicular to the axis of the wheel occurs. The second method can accurately estimate position even when wheel slip parallel to the axis of the wheel occurs. Location of the sensors is investigated in order to minimize errors caused by inaccurate sensor readings. Finally, a method is implemented and tested using a potential field based navigation scheme. Estimates of position were found to be as accurate as dead-reckoning in ideal conditions and much more accurate in cases where wheel slip occurs.

• Journal of the Korean Society for Railway
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• v.12 no.2
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• pp.236-242
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• 2009

This paper presents a numerical analysis method to determine flange contact at variable wheel positions. The shapes of the wheel and rail surface functions with surface parameters. The Newton-Rhapson method for wheel-rail contact can provide fast solutions, but may not yield true values at optimization process with the condition that minimum distance is zero can time-consuming. A compound method, combining the Newton-Rhapson methods the optimization process method is proposed to provide exact solutions efficiently.

• Journal of the korean academy of Pediatric Dentistry
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• v.6 no.1
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• pp.7-13
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• 1979

To evaluate the surface roughness of subgingival area of S. P. crown margins subjected to various polishing procedures, the study was performed by use of metallograph and surface roughness tester. The following results were obtained; 1) Abrasive stone wheel produced the roughest surface ($16.0{\mu}m$). 2) Final polish with rouge after polishing with rubber wheel, subsequent to abrasive stone wheel, produced the smoothest surface ($0.3{\mu}m$). 3) Both polish with rubber wheel after polshing with abrasive stone wheel, and polish with pumice (coarse$\rightarrow$medium$\rightarrow$fine) produced same surface roughness ($0.8{\mu}m$).

• Polymer(Korea)
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• v.31 no.6
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• pp.538-542
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• 2007

This study is on the performance analysis of modified asphalts which were prepared by mixing the asphalt with polymer modifiers of varying compositions which were synthesized by the emulsion polymerization method. Thermal properties of mired asphalt were investigated by DSC (differential scanning calorimetry), and dispersion of modifiers in asphalt was investigated by the fluorescence microscope. Dynamic stability and permanent deformation velocities of mixed asphalt were investigated by wheel tracking measurements. Modifier 6 showed the best results in both penetration test and wheel tracking measurement among investigated modifiers, which supports MMA(methyl methacrylate) moiety in modifiers plays better contribution for the enhancement of asphalt performance than styrene moiety does.

• Journal of the Korean Institute of Intelligent Systems
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• v.7 no.4
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• pp.29-39
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• 1997

A discrete model reference control scheme for a vehicle four wheel steering system(4WS) is proposed and evaluated for a class of discrete time nonlinar dynamics. The schmen employs a neural network to identify the plan systems, wher the neural network estimates the nonlinear dynamics of the plant. The algorithm is proven to be globally stable, with tracking errors converging to the neighborhood of zero. The merits of this scheme is that the global system stability is guaranteed. Whith thd resulting identification model which contains the neural networks, the parameters of controller are adjusted. The proposed scheme is applied to the vehicle active four wheel system and shows the validity and effectiveness through simulation. The three-degree-of freedom vehicle handling model is used to investigate vehicle handing performances. In simulation of the J-turn maneuver, the yaw rate overshoot reduction of a typical mid-size car is improved by 30% compared to a two wheel steering system(2WS) case, resulting that the proposed scheme gives faster yaw rate response andl smaller side slip angle than the 2WS case.

• Journal of the korean Society of Automotive Engineers
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• v.12 no.3
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• pp.21-29
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• 1990

Equipments of passenger cars with modern technologies are gaining their importance. Related with such developments, the four-wheel steering system (4WS) was introduced recently to a few passenger cars in the market. The most important research goal on this new steering system is improvement of active safety, in other words, improvement of handling characteristics of vehicle stability and maneuverability. This paper presents a computer-based study about the effects of 4WS system on the vehicle handling characteristics. A simple bicycle model of 2 d.o.f. is used for the development of four wheel control algorithms of 4WS system, and the rear wheel control strategies are applied to a complex vehicle model of 16 d.o.f. for simulation of selected ISO-driving tests. The 4WS systems, which reduce the sideslip angle at the mass center of vehicle to almost zero, show much improved handling characteristics compared to that of the conventional 2WS system. These 4WS systems, however, result in vehicles with eigen-steer characteristics of extreme understeer behaviour.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.3
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• pp.21-27
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• 1997

This paper aims to clarify the effects of grinding conditions in form grinding of Sr-ferrite with the electro-plated diamond wheel. The main conclusions obtained were as follows. (1) The flexural strength and surface roughness of ferrite became the best at the peripheral wheel speed of 1700 m/min. (2) In the case of the depth of cut larger than 0.4mm, crack layers is induced in the ground surface, and the fracture type of chips exhibits slight ductile mode in the depth of cut smaller than 0.2mm. (3) Whe the depth of cut exceeds 0.6mm, the wheel life becomes extremely severe due to the large chipping and brack- age in the diamond grains. However, at the depth of cut .leq. 0.05mm, the diamond grain shows abrasive wear. (4) The decrease of flexural strength and the increase of surface roughness is in proportion to the increase of the feed rate. (5) Most effective nozzle setting angles with various delivery conditions of the grinding fluid, such as nozzle position .PHI. , flow rate Q, etc., were made clear.

• Journal of Institute of Convergence Technology
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• v.2 no.2
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• pp.40-48
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• 2012

A small domestic desiccant dehumidifier is modelled using effectiveness models for a desiccant wheel and a wet-air condenser. The desiccant wheel and condenser models are used to compose a system model in the form of a set of simultaneous linear algebraic equations, which is solved by Gauss method. The system model is used to simulate the behaviour of a dehumidifier with a 1kW electric air heater. It is found that the maximu COP is about 0.5 and dehumidification capacity is 18kg/day when the ratio of dehumidification area is 0.7. The optimum wheel thickness and face velocity are found 100mm and 1.5m/s, respectively.