Medium- and high-frequency analysis of magnetorheological fluid dampers

Abstract

Controllable dampers based on smart fluids contain internal passages through which the working fluid flows and wherein the controlled pressure drop occurs under the influence of magnetic or electric fields. In this paper, the dynamics of such dampers are analysed through a series of theoretical dynamic models of increasing detail and complexity. The models capture the medium- and high-frequency dynamics of the damping force output of the damper and include the lumped mass of the fluid contained in the internal flow passages, the piston and rod assembly mass, and the compressibility of the fluid and pressurized gas contained within the chambers of the damper. The models are derived in state-space form from which transfer functions and natural frequencies are obtained analytically and then calculated for each of the systems. The results are presented in the form of frequency responses (Bode plots). Finally, the effects of the key geometric parameters of the damper and of the relevant fluid properties on the damper force output dynamics are presented and discussed.