• 한국정밀공학회지
• /
• 제21권11호
• /
• pp.171-178
• /
• 2004

This paper presents vibration characteristics of a wire cut discharge machine in which an electro-rheological brake actuator is used to control the wire tension. The ER brake actuator has several advantages including design simplicity, fast response time and real-time controllability. On the basis of the tension level required in the machine an appropriate size of the ER brake actuator is devised. The ER brake actuator is then incorporated with the machine and the field-dependent wire tension is experimentally evaluated. The straightness of the workpiece is also empirically investigated by changing the intensity of the electric field.

• 유변학
• /
• 제11권2호
• /
• pp.82-90
• /
• 1999

전기유변 유체(electorheological fluid)는 전기장이 가해지면 아주 짧은 시간에 유변 물성이 급격히 변하며 그 응답이 반복적으로 수행될 수 있는 유체이다. 전기유변 유체는 전기장의 세기에 따라 면찰 응력(shear stress)과 점도의 크기를 조절할 수 있고, 짧은 응답시간은 빠른 제어를 요하는 분야에 효과적으로 이용될 수 있지만, 낮은 항복 응력, 조업 온도 범위의 제한성, 전력 소비에 의한 열적 불안정성, 그 외에도 응집, 침전 등의 단점이 있다. 특히, 이 유체가 갖는 항복 응력의 크기와 그 성질은 실제 장치에 응용하는데 중요한 특성이다. 이러한 문제점을 해결하기 위해 면찰 유동(shear flow)이 아닌 압착 유동(squeezing flow)을 고려하게 되었고, 이 유동 하에서의 전기유변 유체의 거동을 이해하기 위해 본 연구에서는 전기유변 유체의 압착 유동에 대한 동적 수치모사를 수행하였다. 고립된 사슬 구조에 대한 수치모사를 통하여 사슬의 위치와 압착 속도를 변화 시키면서 이에 따른 수력학적 힘과 정전기적 힘의 효과를 예측하였으며, 이를 토대로 많은 사슬을 포함한 현탁액 모델에 대한 수치모사를 수행하였다. 그 결과 실험에서 관찰할 수 있는 수직 응력의 증가와 초기 항복 응력의 존재를 확인하였고, 수직 응력의 효과적인 제어는 수력학적 힘과 정전기적 힘 간의 최적화된 조건에서 얻어질 수 있음을 예측하였다. 이러한 수치모사의 개발을 통해 압착 유동을 이용한 전기유변 유체의 응용에 대한 이론적인 토대를 마련하였고, 향후 보다 깊은 이해를 위한 기반을 구축할 수 있었다.

• 한국유변학회:학술대회논문집
• /
• 한국유변학회 2000년도 추계 학술발표회 논문집
• /
• pp.56-60
• /
• 2000

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1993년도 추계학술대회 논문집
• /
• pp.441-445
• /
• 1993

This study addresses the wear characteristics of electro-rheological(ER) fluids which are potential application candidates for various hydraulic systems. As the first step, three different ER fluids are composed and subsequently tested to observe field-dependent Bingham behaviors. The pin-on-disc testing method is then adopted herein herein to investigate the wear rate of the ER fluids with various base liquids and particle concentrations. In addition, friction coefficients for the ER fluids are evaluated with respect to the normal force.

• 한국해양공학회:학술대회논문집
• /
• 한국해양공학회 2000년도 추계학술대회 논문집
• /
• pp.178-183
• /
• 2000

Electrorheological(ER) effect on the dispersive system of polarizable fine powder/dielectric oil has been investigated. The electrical and rheological properties of zeolite and starch based ER fluid were reported. The ER fluids were constructed by mixing zeolite and starch power with two different dielectric oils. Yield stress of the fluids were measured on the couette cell type rheometer as a function of electric fields, particle concetrations, and temperatures. The electric field is applied by high voltage DC power supply. The outer cup is connected to positive electrode(+) and the bob becomes ground(-). And the temperatures the viscosity(or shear stress) versus shear rates were measured. In this experiment shear rates were increased from 0 to $200s^{-1}$ in 2 minutes.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2005년도 추계학술대회논문집
• /
• pp.213-216
• /
• 2005

This paper presents force feedback control performance of a 3DOF haptic device that can be used for minimally invasive surgery (MIS). As a first step, a 3DOF electrorheological (ER) joint is designed using a spherical mechanism. And it is optimized based on the mathematical torque modeling. Subsequently, the master haptic device is manufactured by the spherical joint. In order to achieve desired force trajectories, model based compensation strategy is adopted for the ER master. Therefore, Preisach model fur the PMA-based ER fluid is identified using experimental first order descending (FOD) curves. A compensation strategy is then formulated through the model inversion to achieve desired force at the ER master. Tracking control performances for sinusoidal force trajectory are presented, and their tracking errors are evaluated.

• 한국윤활학회:학술대회논문집
• /
• 한국윤활학회 2003년도 학술대회지
• /
• pp.229-234
• /
• 2003

As electrorheological fluid(ER fluid) has a characteristic that apparent viscosity varies when electric field applied, so rheological characteristic(yield stress & viscosity) changes in proportion to the electric field applied and the response time is very short within a few miliseconds . In case of using ER fluid for journal bearing as lubricant, it is estimated that it's possible to realize very effective journal bearing system that is not complicate and has a very quick response time. It is necessary to examine the influence of rheological characteristic that varies with electric field applied on bearing characteristic to apply ER fluid to journal bearing, however there are few studies for about that. As for the journal bearing, it comes under high shear flow mode that has shear rate range of $10^3\~10^4s^{-1}$ because rotational speed is very high and clearance is small. But most of the studies for about ER fluid issued until now is about the range of $10\~10^2s^{-1}$. So, there are a lot of difficulties to understand the characteristic offish shear flow mode and furthermore it is restricted to make an experiment for about the characteristic of ER fluid because of the limitation of experimental equipment. The equipment was prepared to make an experiment lot high shear flow mode that has the range of $10^3\~10^4s^{-1}$ using ER fluid that is composed of silicon oil with dispersed particle of starch. Using the above system, the fluid characteristic of ER fluid was studied.

• 전산구조공학
• /
• 제16권3호
• /
• pp.33-40
• /
• 2003

• 기계와재료
• /
• 제14권4호통권54호
• /
• pp.35-48
• /
• 2002

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2007년도 춘계학술대회논문집
• /
• pp.1125-1130
• /
• 2007

This paper presents a maneuver analysis of a full-vehicle featuring electrorheological (ER) suspension and ER brake. In order to achieve this goal, an ER damper and an ER valve pressure modulator are devised to construct ER suspension and ER brake systems, respectively. After formulating the governing equations of the ER damper and ER valve pressure modulator, they are designed and manufactured for a middle-sized passenger vehicle, and their field-dependent characteristics are experimentally evaluated. The governing equation of motion for the full-vehicle is then established and integrated with the governing equations of the ER suspension and ER brake. Subsequently, a sky-hook controller for the ER suspension and a sliding mode controller for the ER brake are formulated and implemented. Control performances such as vertical displacement and braking distance of vehicle are evaluated under various driving conditions through computer simulations.