Characterization of Output Torque of a Permanent Mag-netbased MRF Clutch with a Field Blocking Mechanism

Abstract

Although it is not an impossible task, previous work [1], [2] on magnetorheological fluid (MRF) clutches has proved that the prediction of the torque transmission capacity is not a straight forward process. The prior MRF clutch presented in [3] also showed a big discrepancy between expected torque capacity of the clutch and actual measured torque. In this work, a new MRF clutch has been proposed and fabricated, with the expectation that its torque transmission capacity would be larger, as the clutch itself is also larger. This new clutch is a cylinder-based clutch with four MRF layers, which uses permanent magnets, but uses a steel cylinder which vary the magnetic field by covering the magnets. With the use of simulations and mathematical models, study of the MRF clutch is presented in this paper on how accurately the output torque can be modelled. Magnetostatic simulation The clutch with its MRF layers and with the field-blocking steel cylinder at several different positions were simulated using ANSYS Maxwell. Since the datasheet of the used MRF shows that for weaker fields the relation between the magnetic field and the yield stress is nearly linear, the average magnetic field of each layer was used to calculate the yield stress at that particular layer.