Nonlinear Parameter Identification of an Electro-Rheological Fluid Damper

Abstract

Parameters for a nonlinear model of an electro-rheological (ER) damper were identified from experimental data. The ER fluid used in the test damper was composed of zeolite particles with diameters less than 10 microns suspended in 20 centistoke silicon oil. Motion of the damper piston forced the fluid to flow through annular gaps between three concentric cylindrical electrodes. Experiments were performed on the damper by using a fatigue testing machine made by Testline Mechanical Test Systems to provide a controlled movement of the damper. The measured data included the damper force, the piston displacement as well as the voltage applied to the damper electrodes and the resulting current. The parameters were identified using a quasi-linearization technique which has been found suitable for similar nonlinear parameter model identification problems. The model used in the study included the effects of fluid inertia, as well as viscous and Coulomb friction components. Results of the identification indicate that, although the parameters generally were found to vary from one oscillation cycle to the next, average parameters were able to predict the force in the damper as a function of damper motion and the applied voltage. Some evidence suggests that the predictive capabilities of future models may be improved by adding fluid compressibility and hysteresis to the model.