Modeling asymmetric hysteretic properties of an MR fluids damper

A generalized model is synthesized to characterize the asymmetric hysteretic force-velocity properties of a magneto-rheological (MR) fluid damper as a function of the command current, excitation frequency and displacement amplitude, on the basis of symmetric and asymmetric sigmoid functions. The synthesis incorporates the peak force, peak velocity, transition velocity leading to force-limiting and the corresponding force, low and high velocity rise, and the hysteresis, in compression as well as rebound under different levels of command current. The model parameters are identified using the measured and modified data for a MR-damper. The validity of the model is examined by comparing the model results with the measured data for both dampers over a broad range of excitation conditions, and applied current in case of the MR damper. It is concluded that the proposed model could be effectively applied to characterize the hysteretic nonlinear properties of a controllable MR damper for development of an optimal controller in vehicle suspension system.