Papers by Author: Kum Gil Sung

Abstract: This paper presents ride comfort analysis of a full-vehicle featuring controllable magnetorheological (MR) shock absorbers. In order to achieve this goal, two flow mode MR shock absorbers (one for front suspension; one for rear suspension) are designed using an optimization methodology based on design specifications for a commercial passenger vehicle. The optimization problem is to find optimal geometric dimensions of the magnetic parts for the front and rear MR shock absorbers in order to improve the performance such as damping force. After manufacturing the proposed MR shock absorbers, their field-dependent damping forces are experimentally evaluated. The governing equation of motion for the full-vehicle is then established and integrated with the model of the MR shock absorbers. Subsequently, skyhook controllers for the MR suspensions are formulated and implemented. Ride comfort performances of the full-vehicle installed with the proposed MR shock absorbers are evaluated under bump and random road.

Abstract: This paper presents damping force control performances of a magnetorheological (MR) damper via new control strategy considering hysteretic behavior of the field-dependent damping force. In order to achieve this goal, a commercial MR damper which is applicable to passenger vehicle is adopted and its field-dependent damping force is experimentally evaluated. Since the field-dependent damping force shows the hysteretic behavior which significantly affects to control characteristics of the system, Preisach hysteresis model for the MR damper is established and its first order descending (FOD) curves are experimentally identified. Subsequently, a feed-forward compensator strategy for the MR damper is formulated and damping force control is evaluated. In addition, vibration control performances are experimentally evaluated with quarter-vehicle test facility.

Abstract: In this study, the dynamic fatigue characteristics of chemical starch-based ER fluid are experimentally investigated. A flow mode type apparatus is manufactured to activate the flow motion of the ER fluid. After evaluating the field-dependent Bingham property, three important dynamic fatigue characteristics; yield stress, current density and response time of the ER fluid are investigated as a function of the operating cycle. The dynamic operation for the flow motions is undertaken up to one million cycles and electric voltage is applied to the electrodes. In addition, the change of the particles of the ER fluid is microscopically observed to advocate the variation of the yield stress.