DMDMRA: a Dual Multi-drum Magnetorheological Actuator Towards Small-Scale, High-Torque Actuation

Designing small-scale, high-torque magnetorheological (MR) actuators remains a challenge, with the main difficulty being how to maximize the effective shear area within tightly constrained volumes. To address this, a novel shared-flux dual multi-drum topology is proposed and investigated, in which an electromagnetic coil activates the MR fluid regions on both sides to form eight drum-type shear gaps, thereby improving the torque-to-volume ratio (TVR) and torque-to-mass ratio (TMR). This paper advances the dual multi-drum topology via figures-of-merit modeling, parametric evaluation, and experimental characterization. Analytical models for braking torque, volume, mass, and power consumption are derived to establish design-oriented relations and performance envelopes. The influence of drum length, a critical design parameter in the proposed topology, is comprehensively evaluated via finite element analysis, thereby guiding the design trade-offs. An optimized dual multi-drum MR actuator (DMDMRA) prototype (Ø31.8×46 mm, 215.6 g) was fabricated. It achieved a peak torque of 1368.48 mN·m and an off-state torque of only 9.12 mN·m, yielding a TVR of 37.48 kN/m² and a TMR of 6.35 N·m/kg. These results highlight its notable TVR and TMR advantages over other MR actuators of comparable size and further demonstrate the feasibility of the proposed topology.