• 한국소음진동공학회논문집
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• 제23권5호
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• pp.445-455
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• 2013

A new linearization model for MR dampers is analyzed. The nonlinear hysteretic damping force model of MR damper can be modeled as a hyperbolic tangent function of currents, positions, and velicities, which is an algebraic function with constant parameters. Model parameters can be identified with numerical method using experimental force-velocity-position data obtained from various operating conditions. The nonlinear hysteretic damping force can be linearized with a given slope of damping coefficient if there exist corresponding currents to compensate for the nonlinearity. The corresponding currents can be calculated from the inverse model when the given linear damping force is set equal to the nonlinear hysteretic damping force. The linearization controller is realized in a DSP controller such that the corresponding currents to satisfy a given damping coefficient should be calculated. Experiments show that the current inputs to the MR damper produce linearized damping force with a given slope of the damping coefficient.

• 한국구조물진단유지관리공학회 논문집
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• 제26권4호
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• pp.1-10
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• 2022

이 연구에서는 강재 스프링을 감쇠 장치로써 사용 가능성을 평가하기 위해서, 강재 스프링의 인장 및 반복하중 실험을 수행하였다. 주요 실험변수는 강재의 종류(SAE9254 및 SS275), 스프링상수(700 N/mm, 1,000 N/mm 및 1,400 N/mm) 및 SAE9254의 열처리 유·무이다. 인장 실험 결과, SAE9254로 제작된 강재 스프링의 설계 스프링상수와 측정 스프링상수의 비는 1.08 ~ 1.13이며, SS275로 제작된 강재 스프링의 설계 스프링상수와 측정 스프링상수의 비는 0.86 ~ 0.97로 측정되었다. 항복 이후 열처리 유·무에 따른 SAE9254로 제작된 스프링의 하중-변위 관계 기울기는 약 240 ~ 251 kN/mm 및 92 N/mm 이었으며, SS275로 제작된 스프링의 하중-변위 관계 기울기는 거의 0이었다. 반복하중 실험 결과에서 모든 실험체는 KDS 41 17 00 (2019)에서 요구하는 변위 의존형 감쇠 장치의 적합 조건인 변위 원점에서의 하중 조건, 최대변위에서 하중 조건 그리고 에너지 소산 능력 조건을 모두 만족하였다. 그리고 열처리 안 된 SAE9254 및 SS275로 제작된 강재 스프링의 등가 감쇠비는 열처리 된 SAE9254로 제작된 스프링에 비해 각각 약 2.8배 및 1.9배 높은 수준이었다.

• 한국자동차공학회논문집
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• 제10권3호
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• pp.192-200
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• 2002

Semi-active suspension systems are greatly expected to be in the mainstream of future controlled suspensions for passenger cars. In this study, a continuous variable damper for a passenger car suspension is developed, which is controlled actively and exhibits high performance with light weight, low cost, and low energy consumption. To get fast response of the damper, reverse damping mechanism is adapted, and to get small pressure change rate after blow-off, a pilot controlled proportional valve is designed and analyzed. The reverse continuous variable damper is designed as a HS-SH damper that offers good body control with reduced transferred input force from tire, compared with any other type of suspension system. The damper structure is designed, so that rebound and compression damping force can be tuned independently, of which variable valve is placed externally. The rate of pressure change with respect to the flow rate after blow-off becomes smooth when the fixed orifice size increases, which means that the blow-off slope is controllable using the fixed orifice size. The damping force variance is wide and continuous, and is controlled by the spool opening, of which scheme is usually adapted in proportional valves. The reverse continuous variable damper developed in this study is expected to be utilized in the semi-active suspension systems in passenger cars after its performance and simplicity of the design is confirmed through real car test.

• 한국해안·해양공학회논문집
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• 제29권6호
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• pp.369-381
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• 2017

쇄파역에서 흔히 관측되는 왜도된 비선형 파랑은 정현파에 비해 상대적으로 큰 관성력을 지녀 투과율에 미치는 영향이 상당할 것으로 추정되어왔다. 본고에서는 이러한 추론을 확인하기 위해 왜도가 1.02에서 1.032에 분포하는 총 여섯 개의 파랑을 대상으로 한 수치모의를 수행하였다. 수치모의는 OpenFoam 기반 Tool box인 ihFoam을 사용하여 수행하였으며, 왜도된 비선형 파랑은 경사가 1:30인 천퇴를 이용하여 유도하였다. 투수층에서의 유동은 Navier Stokes Eq.에 추가 항력을 도입하여 해석하였으며, 모의결과 왜도된 비선형 파랑은 정현파에 비해 큰 관성력으로 인해 상대적으로 큰 투과율을 지니는 것으로 모의되었다. 또한 Porous층에서의 Damping으로 인한 파속변화 여부를 살펴 보기위해 Damping이 반영된 천수방정식으로부터 분산관계식을 새로이 유도하였으며, 그 결과 투과성 방파제에서의 파형과 마찰력 사이의 위상차가 파속에 영향을 미치는 것으로 보인다.

• 한국소음진동공학회논문집
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• 제27권1호
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• pp.65-71
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• 2017

This work presents a comparative work on the ride comfort of a quarter car suspension system between two different magneto-rheological (MR) dampers; one is conventional type without bypass hole and the other is featured by several bypass holes in the piston. As a first step, two different MR dampers are designed on the basis of the governing equation and manufactured with same geometric dimensions except the bypass holes. After investigating the field-dependent damping properties, two dampers are installed to the quarter car suspension system. The suspension model is then derived and a sky-hook controller is implemented to identify vibration control performance under random road. It is shown that the suspension system with MR damper featured by the bypass holes can provide much better ride quality than the case without the bypass holes. This is validated via experimental implementation.

• 한국자동차공학회논문집
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• 제15권6호
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• pp.114-119
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• 2007

Because the small trailers do not have the main brake system, it is difficult to gain the effective braking performance of the trailers while driving them. Especially it is very hard to brake them on the slope road condition. So we have technically developed Inertia Braking System for the military trailers which have not main braking system. Inertia Braking System is designed to be activated by the inertia force of trailer. It consists of the brake rod, damping cylinder, hand brake lever and brake cables. We have tested the trailer's braking performance. As a result, we have showed that the trailer's braking performance of the trailer equipped with Inertia Braking System, the road driving performance and the braking safety capability are improved dramatically. And we hope that it is rare to happen the accident while driving.

• 한국지진공학회논문집
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• 제21권5호
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• pp.255-264
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• 2017

Dynamic numerical simulation of pile-supported slab track system embedded in a soft soil and embankment was performed. 3D model was formulated in a time domain to consider the non-linearity of soil by utilizing FLAC 3D, which is a finite difference method program. Soil non-linearity was simulated by adopting the hysteric damping model and liner elements, which could consider soil-pile interface. The long period seismic loads, Hachinohe type strong motions, were applied for estimating seismic respose of the system, Parametric study was carried out by changing subsoil layer profile, embankment height and seismic loading conditions. The most of horizontal permanent displacement was initiated by slope failure. Increase of the embedded height and thickness of the soft soil layer leads increase of member forces of PHC piles; bending moment, and axial force. Finally, basic guidelines for designing pile-supported slab track system under seismic loading are recommended based on the analysis results.