Novel magnetorheological damper with outstanding fail-safe characteristics

A magnetically hybrid damper based on magnetorheological (MR) fluids, which includes electro- and permanent magnets, is presented. A demonstrator of this novel MR damper principle was manufactured and its performance in terms of the damping force under various conditions was studied. With the permanent magnet it is possible to generate a damping force of about 1400 N without a current generated in the coil and without any energy consumption. The maximum achievable force of the novel damper amounts to about 4000 N and the minimum damping force is around 400 N, depending on the polarity of the current in the coil. Damping forces were also calculated using a simple model and the results are in rough accordance with the experimental data. Furthermore, the velocity dependence of the damping force was studied, whereas the frequency of the sinusoidal excitation was varied between 1 and 5 Hz. The outstanding fail-safe behavior of the novel MR damper is achieved by the fact that a medium damping force is generated in the powerless state, in contrast to the known MR dampers which work only with electromagnets.