A study of an inner bypass magneto-rheological damper with magnetic bias

摘要

In this paper, a type of magneto-rheological (MR) damper with an inner bypass and magnetic bias is proposed to fulfill the requirements of both large scalability and low base-damping, which are critical for vibration suppression. With the magnetic bias feature, low base-damping and large scalability can be obtained by the bi-directional excitation of the applied current. The inner bypass feature can eliminate or alleviate the flow block that occurs in the damping gap, however keeping the advantage of suitability for vehicle suspension installation. In contrast to the original mixed mode, the new MR damper adds a concentric damping gap in the piston, which is controlled by the magnetic field, while the original gap will be free of any magnetic field because of the shielding by non-magnetic material. The magnetic bias in the added gap is obtained by the inclusion of a permanent magnet in the piston. A magnetic analysis is carried out to verify the magnetic distribution under permanent and electro-magnetic excitation. Based on the fabricated prototype, both quasi-steady and dynamic tests are carried out, and it is shown that the MR damper achieves bi-directional operation of the damping force with scalability up to 8, and that the flow block is partly alleviated in a high applied current.