• 대한조선학회논문집
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• 제56권6호
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• pp.550-558
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• 2019

The roll motion of a general vessel, which is more influenced by resonance as compared to other motions, adversely affects the passenger and hull. Therefore, reducing the roll motion through an anti-rolling system is critical, and most ships use various devices such as anti-rolling tanks, bilge keels, and fin stabilizers to accomplish this. In this study, a simplified model is developed for the application of an anti-rolling device for unmanned semi-submersible vessels. The applied anti-rolling device is installed on the stern and stem of a ship using a pair of servo motors with added weight, and the motor is controlled through the Arduino. The moment of the motor is designed and implemented based on a mathematical model such that it is calculated through the restoring force according to the heel angle of the ship. The performance of the proposed system was verified by utilizing the roll damping coefficient calculated by the free-roll decay test and logarithmic decrement method and was validated by a towing tank test. The system is expected to be used for unmanned vessels to perform sustainable missions.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1091-1097
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• 2008

Roll-to-roll based manufacturing plays an important role in producing devices at high speed with lower production cost in printed electronics and publishing industry. Web lateral control is one of the most important factors in improving the quality of product and contributes a considerable point in making devices at micrometer-level accuracy. In recent years, most algorithms proposed for web lateral control base on the Shelton‘s model for designing the feedback control system using the PI controller. Experimental results showed that the existing models do not fully describe the characteristics of the lateral dynamics for some typical operating conditions and so result in poor control algorithms. In this paper, a new lateral control algorithm is proposed for web lateral control system based on back-stepping approach. The outcome of this study proves the reliability throughout simulation results in Matlab/Simulink and comparison with the algorithms based on the existing results.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.583-584
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• 2006

Printing technology has begun to get into the spotlight in many ways due to the low cost effectiveness to existent semi-conductor process. It also has very useful application areas, not only paper printing but also patterning for LCD color tilter, Photovoltaic patterning, RFID antenna, OLED, and so on. In this study, an apparatus of gravure offset printing was developed for fine line width printing. The pattern was composed of $20{\mu}m$ size of continuous lines of which pitch size was $40{\mu}m$. The printed pattern shows that it is possible to make around $20{\mu}m$ line-width printing pattern. The roll-to-roll printing system for fine line-width printing based on primary experiment is presented. For testing of multi-layer printing, the system was designed to be capable of printing two different materials from each printing unit using gravure-offset printing method and have a function of alignment of two printed materials.

• International Journal of Automotive Technology
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• 제8권4호
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• pp.445-453
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• 2007

This paper presents a robust controller design approach for improving vehicle dynamic roll motion performance and guaranteeing the closed-loop system stability in spite of vehicle parameter variations resulting from aging elements, loading patterns, and driving conditions, etc. The designed controller is linear parameter-varying (LPV) in terms of the time-varying parameters; its control objective is to minimise the $H_{\infty}$ performance from the steering input to the roll angle while satisfying the closed-loop pole placement constraint such that the optimal dynamic roll motion performance is achieved and robust stability is guaranteed. The sufficient conditions for designing such a controller are given as a finite number of linear matrix inequalities (LMIs). Numerical simulation using the three-degree-of-freedom (3-DOF) yaw-roll vehicle model is presented. It shows that the designed controller can effectively improve the vehicle dynamic roll angle response during J-turn or fishhook maneuver when the vehicle's forward velocity and the roll stiffness are varied significantly.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 제7회 압연 심포지엄
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• pp.19-22
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• 2009

It is essential to predict the deformed roll profile for the prediction of the strip profile in rolling process. The work roll of the Sendzimir mill has a small diameter in comparison to a barrel length, so that it is well deformed by the rolling pressure. Also it has a complex roll system, so it is difficult to analyze the roll deflection. In this paper, 3D finite element method is used for the analysis of the roll deflection of the Sendzimir due to the contact between rolls. But it takes much time to get the results, so that the on-line model to evaluate the radial deformation of a roll is developed on the basis of the finite element method.

• 대한기계학회논문집B
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• 제26권5호
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• pp.648-657
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• 2002

This paper presents a numerical analysis on the solidification characteristics in twin-roll strip casting. Unstructured fixed-grid system was employed to deal with phase change. Melting of pure gallium was analyzed to confirm the validity of present program in both structured and unstructured grid systems. An algorithm for simultaneous calculation of the temperature in the roll and the molten metal pool was developed. The flow field in the pool and heat transfer features between pool and roll were shown. The effect of process parameters was also studied. Since the geometry of the molten metal Pool significantly deforms along the casting direction, unstructured grid system is more efficient. The unstructured grid system gives almost the same accuracy, even though the number of grids is only 60% of the structure done.

• Advances in Automotive Engineering
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• 제1권1호
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• pp.1-20
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• 2018

The aim of this study is the optimization of the parameters of interconnected Hydro-Pneumatic (HP) suspension system of a three-axle vehicle for ride comfort and handling. For HP suspension systems of equivalent vertical stiffness and damping characteristics, interconnected HP suspension systems increase roll and pitch stiffness and damping characteristics of the vehicle as compared to unconnected HP suspension systems. Thus, they result in improved handling and braking/acceleration performances of the vehicle. However, increased roll and pitch stiffness and damping characteristics also increase roll and pitch accelerations, which in turn result in degraded ride comfort performance. Therefore, in order to improve both ride comfort and vehicle handling performances simultaneously, an optimum parameter set of an interconnected HP suspension system is obtained through an optimization procedure. The objective function is formed as the sum of the weighted vertical accelerations according to ISO 2631. The roll angle, one of the important measures of vehicle handling and driving safety, is imposed as a constraint in the optimization study. Upper and lower parameter bounds are used in the optimization in order to get a physically realizable parameter set. Optimization procedure is implemented for a three-axle vehicle with unconnected and interconnected suspension systems separately. Optimization results show that interconnected HP suspension system results in improvements in both ride comfort and vehicle handling performance, as compared to the unconnected suspension system. As a result, interconnected HP suspension systems present a solution to the conflict between ride comfort and vehicle handling which is present in unconnected suspension systems.

• 대한기계학회논문집A
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• 제27권2호
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• pp.327-333
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• 2003

Most of shape defects in steel strip are originated from the structure of rolling mill itself. For instance, strip crown occurs when the work roll is deformed by the bending moment induced on roll chocks. To get rids of the shape defects, it is necessary to increase the stiffness of rolling mill. The structure change of back-up roll is one of alternative ways to increase the mill stiffness without facility revamping from 4 high mill to 6 high mill. In this research work, the new back-up roll was developed and can be used in any type of 4 high mill to reduce the strip shape defects. The developed back-up roll consists of sleeve, arbor and phase angle adjusting system for arbor. The circumference of arbor is specially machined to adapt the strip width change during rolling. The experimental cold rolling test was done to prove the effectiveness of newly developed back-up roll. The experimental rolling results show that the new back-up roll has more powerful performance in reducing the shape defects than conventional back-up roll. It was also found that the new back-up roll has higher stability for shape control. In addition to, the only sleeve surface needs to be reground and changed in most cases, so that the maintenance cost can be greatly reduced.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 추계학술대회 논문집
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• pp.91-94
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• 2005

With increasing demands for large-scale micro-optical components in the field of digital display, the establishment of large-scale fabrication technology fur polymeric patterns has become a priority. The starting point of any polymer replication process is the mold, and the mold often has flat surface. However, It is very hard to replicate large-scale micro patterns using the flat mold, because the cost of large-scale flat mold was very high, and some uniformity and releasing problems were often occurred in large scale flat molding process. In this study, a UV roll imprinting system to overcome the financial and fabrication issues of large-scale pattern replication process was designed and constructed. As a practical example of the system, a lenticular lens with radius of curvature of $223{\mu}m$ and pitch of $280{\mu}m$, which was used to provide wide viewing angle in projection TV, was designed and fabricated. The roll stamper was fabricated using direct machining process of aluminum roll base. Finally, the shape accuracy and uniformity of roll imprinted lenticular lens sheet were measured and analyzed.

• 소성∙가공
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• 제16권3호
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• pp.201-209
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• 2007

Generally, the forming process of suspension system parts have been considered only considered with the formability and have not been considered with the durability of suspension system. But the durability of suspension system is very important characteristic for the dynamic performance of vehicle. Therefore, the suspension system should be manufactured to consider the durability as well as the formability. This paper is about an optimum forming process design with the effect of section properties to consider the roll durability of torsion beam type suspension. In order to determine the tube hydroforming process for the satisfaction the roll durability, the stamping and hydroforming simulation by finite element method were performed. And the results from finite element analysis and roll durability examination showed the tube hydroforming process of torsion beam is optimized as satisfying the durability performance.