• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2001년도 추계학술대회(한국공작기계학회)
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• pp.91-96
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• 2001

When it is considered that many vehicle rides on the road and ride quality is an important method to evaluate vehicle performance with handling, running-over-bump manoeuvre may be suitable for testing ride quality. In this paper, a computed model has roughly steering system and lumped mass, connected by joint each rigid body, and suspension that has beam elements and has shock absorber as force element to represent nonlinear characteristics. A computer simulations for passing over a bump were made with two velocities. One side of vehicle passed over bump in due consideration of driver's habit that driver is subject to avoid a bad ride quality. On simulation, vertical acceleration, pitch angle and roll angle were measured at the mass center of chassis each case.

• Tribology and Lubricants
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• 제14권1호
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• pp.85-93
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• 1998

The Bair & Winer's limiting shear stress rheological model is incorporated into the Reynolds equation to successfully predict the traction and film thickness for an isothermal line contact using the primary rheological properties. The modified WLF viscosity model and Barus viscosity model are also adapted for the realistic prediction of EHD tractional behavior. The influences of the limiting shear stress and slide-roll ratio on the pressure spike, film thickness, distribution of shear stress and nonlinear variation of traction are examined. A good agreement between the disc machine experiments and numerical traction prediction has been established. The film thickness due to non-Newtonian effects does not deviate significantly from the fdm thicknesss with Newtonian lubricant.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1994년도 추계학술대회 논문집
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• pp.584-589
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• 1994

A time-varying nonlinear mathematical model was derived to consider the effect of change in roll radius on tension varation during winding and unwinding. A variable-gain PID controller was designed for tension control at start and stop in a multi-span continuous process system. The controller gains are updated at every control loop as roll radii continuously change. Computer simulation was carried out by using the mathematical model and the controller developed for a typical operating condition including acceleration and deceleration. When the variable-gain PID controller was used, the tension control performance was improved compared with that of existing control method during start-up and stop.

• 소음진동
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• 제7권2호
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• pp.239-246
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• 1997

This paper presents an active suspension control algorithm to improve the suspension performance trade-offs between riding comfort and handling stability. In this paper, a hybrid control scheme is proposed, the idea of which is that sliding mode control is used for nonlinear hydraulic system and the skyhook control is applied to control the vehicle behavior. The parameter variations in hydraulic system are considered for the robust controller design. The performance of the proposed control method is evaluated by simulation and experiments based on a half car roll model which can reveal both heave and roll behavior.

• 한국해양공학회지
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• 제5권2호
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• pp.51-57
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• 1991

불규칙 해상에서 선박의 큰 횡요각의 예측이 중요한 과제로 대두 되고 있다. 본 논문에서는 통계적 해석에 의한 이의 예측 방법을 제시한다. 즉 주어진 비 선형 횡요운동 방정식으로 부터 배의 횡요각과 각속도의 결합 확률 밀도 함수를 구하는 방법을 도입하고 각종 계수들의 값의 변화에 따른 예측 결과를 다른 논문에서 제시한 시뮬레이션 결과와 비교하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국내학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.1076-1079
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• 1993

A fuzzy digital controller is combined an autopilot system for compensating the cross coupling effect of the induced roll due to the dynamic characteristic of three fin torpedo. However the utilization of fuzzy chip has many interfacing problems with typical microprocessors of the guidance and control unit. Since a fuzzy digital controller on a microprocessor uses a finite word length A/D converters arul D/A converters, ADC and DAC may generate nonlinear effects such as deadband and limit cycle phenomena. In this paper, the robustness of fuzzy digital controller is tested with ADC a finite word length.

• 한국생산제조학회지
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• 제9권5호
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• pp.65-72
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• 2000

This paper presents the study of the tension control in a web transfer system. In this study the sliding mode controller is applied to a time-varying nonlinear mathematical model. The model was derived to consider the effects of changing the roll radius in tension variation during winding and unwinding. The uncertainty in modeling may be due to unmodelled dynamics, on variations in system model. Designed sliding mode controller made the system error always staying in the suggested surface from the beginning. Through this, system is maintained to be robust against a disturbance and uncertainty. To verify the designed controller has a good performance, various inputs such as desired velocity, step input, and trapezoidal input are applied. When the sliding mode controller was used, the system(the tension control) performance was improved comparing to the PID controller. The robustness of the controller with respect to an estimation error was verified through simulations.

• 한국정보통신학회논문지
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• 제3권4호
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• pp.895-905
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• 1999

This paper identifies a linear time-invariant mathematical model of each stand of a five-stand tandem cold mill to design a robust $H_\infty$ thickness controller by applying input and output data sets to N4SID (Numerical algorithms for Subspace State Space System Identification) method. The input-output data sets describe interstand interference in the process of tandem cold rolling and are obtained from a nonlinear simulator of the tandem cold mill. In result, it is shown that the identified model well approximates the nonlinear model than a Taylor linearized model. Furthermore, uncertainties including roll eccentricity and incoming strip variation are quantitatively analyzed from the plot of maximum singular values.

• 한국해양공학회지
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• 제7권2호
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• pp.141-149
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• 1993

삼 자유도를 가진 부유물체의 동적 응답을 이론적으로 연구하였다. 평면내 방향 운동모우드에 대한 지배방정식을 선형화한 후, 그들의 조화해를 평명밖 방향 운동모우드의 방정식과 연성시켰다. 그렇게 해서 주어지는 방정식은 시간에 따라 변화하는 계수를 가진 형태로서, 평면밖 방향의 운동만을 보일 것으로 예측되는 부유물체가 평면밖 방향의 운동을 보일 수도 있음을 밝혔다. 동역학적 불안정성과 그 결과로 나타나는 평면밖 방향의 대진폭 운동을 보이고 있다. 본 결과는 주기적으로 동요하는 부유물체가 서로 연성된 운동을 하는 현상으로도 해석할 수 있다.

• 대한조선학회논문집
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• 제30권4호
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• pp.39-45
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• 1993

불규칙 해상에서의 선체의 횡동요운동을 해석하기 위하여 등가선형화방법을 사용 하였다. 일자 유도 선형 횡동요운동 모델에다가 2차의 비선형 감쇠항과 3차 및 5차의 비선형 복원 모멘트를 추가 하였으며 불규칙 기진 모멘트는 가우스 백색잡음으로 가정 하였다. 등가선형화 방법을 사용하여 예측한 응답의 통계적 특성을Simulation 결과와 비교 하였다.