H∞ control of electrorheological suspension system subjected to parameter uncertainties

Vehicle suspension is normally used to attenuate unwanted vibration from various road conditions. The successful suppression of the vibration leads to the improvement of ride comfort as well as steering stability of the vehicle. One of attractive candidates to formulate successful vehicle suspension is to use electrorheological (ER) damper. This paper presents robust control performances of ER suspension system subjected to parameter uncertainties associated with sprung mass of the vehicle and time constant of the ER damper. After identifying dynamic bandwidth of a cylindrical ER damper operated with two different ER fluids (one has fast response characteristic, while the other slow response characteristic), a quarter car model is established by incorporating with time constant of the damping force. A robust H. controller, which compensates the sprung mass and time constant uncertainties, is designed in order to suppress unwanted vibration of the vehicle. Control responses such as vertical acceleration of the sprung mass are presented in time and frequency domains. In addition, the effect of time constant of the damping force on the vibration control performance is investigated by undertaking a comparative work between fast and slow dynamic characteristics of the ER damper. (C) 2002 Elsevier Science Ltd. All rights reserved.