Magneto-Rheological Fluid (MRF) is a functional fluid in which flow characteristics change into magnetic force due to its magnetic particles. When the semi-active control device does not use MRF for a long time, precipitation of magnetic particles and abnormal control force occur. Thus, Electro Magneto-Rheological Fluid (EMRF), which improves the precipitation of magnetic particles for MRF and exhibits existing control performance, was developed in this study. First, the optimal mix proportion ratio was selected by conducting a precipitation experiment and a controlled force test by varying the content of grease based on the existing MRF components. Also, EMRF was applied to the shear-type damper to evaluate the control performance when applied to the control device. The cylinder-type damper was developed to apply to the structure, and control performance evaluation was conducted. The result confirmed that the precipitation of the magnetic particles was improved, while the damper using EMRF exhibited excellent control performance.

In this paper, the damping force of MRF(Magneto-Rheological Fluid) damper using Bingham-plastic model is studied and the performance of quarter car model using this damper is numerically analyzed. As a control algorithm, the sky-hook control is used for its convenience and effectiveness. The transmissibility of sprung mass and unspung mass is compared to that with the conventional passive damper and the feasibility of MRF damper is evaluated. And the design concept of fail-safe MRF damper is suggested to provide the damping force of conventional passive damper level in the case of controller malfunction. The control current and damping force is analyzed passing over the harmonic bumper.