SIMULATION AND EXPERIMENTAL-STUDY OF A SEMIACTIVE SUSPENSION WITH AN ELECTRORHEOLOGICAL DAMPER

Various control strategies for a semi-active suspension system with an electrorheological (ER) damper were studied using computer simulation techniques, as well as experimentally using a quarter-car model test facility. The control strategies examined included those primarily des igned for enhancing ride comfort and for improving road holding. It wa s found that the strategies designed for enhancing ride comfort do not necessarily provide improved road holding characteristics, and vice v ersa. Consequently, various composite control strategies for improving both ride comfort and road holding were investigated. Experimental in vestigations showed that the damping characteristics of an electrorheo logical damper depend not only on the electrical field strength but al so on the frequency of excitation. For the electrorheological fluid us ed in the study, the equivalent damping ratio decreases significantly with the increase in the frequency of excitation. This is primarily du e to the fact that the shear ratio of the fluid used, which is the rat io of the shear strength at a given electrical field strength to that without applied electrical field, decreases with the increase in the s hear rate. This behavior must be taken into account in the development of electrorheological dampers. Furthermore, at high frequencies, the duration of the applied voltage with any of the control strategies exa mined is very short. As a result, there is little difference in the me asured performance of the semi-active suspension with different contro l strategies examined over a wide range of frequency. To achieve the p otential of an ER fluid damper, improvements in the mechanical behavio r of ER fluids are a key factor.