Design and evaluation of a small-scale multi-drum magnetorheological brake

Magnetorheological fluid, whose rheological properties can be continuously and reversely changed, is a new-type smart material. Based on magnetorheological fluid, magnetorheological brake is a potential actuation method in haptics due to its desirable features, such as inherent passiveness and high compactness. Most of the existing magnetorheological brakes are powerful enough, but they are too bulky and heavy. If they were smaller and lighter, they would be more favourable for haptics. In this article, a small-scale yet powerful magnetorheological brake was designed, modelled and evaluated. We adopted a novel multi-drum architecture to activate more shearing areas within a limited volume. To obtain an ideal sealing effect and reduce the off-state friction, the ferro-fluidic sealing technique was used. The ferro-fluidic sealing assemblies can be assembled from both sides of the shaft. The current–torque model of this brake was derived to predict the torque output based on the current input. The optimal design has the diameter of 28 mm and the width of 23.5 mm. It can provide the maximum and minimum torque of 403 and 4 N mm, respectively, giving the torque–volume ratio of 27.864 kN/m 2 and the dynamic range of about 40 dB with the 54 ms time constant.