Development of a multilayered wide-ranged torque magnetorheological brake

This paper presents the design of a multilayered magnetorheological brake from modelling to prototyping and characterization. A magnetostatic model intended to provide a specific magnetic flux density over a fluid gap regardless of the dimensions of the fluid surface is proposed. The ferromagnetic path and the coil are dimensioned in consequence. The model needs only three inputs to completely define the brake, i.e. the number of fluid gaps, the inner radius of the smallest fluid gap and the fluid gap depth. The evaluation criteria are defined by the torque density, the controllability and the reactivity, described as a function of the dimensions and the number of fluid gaps. The model has been optimized to improve the torque density. The brake has four fluid gaps and has been built and characterized. The expected torque when the fluid reaches the desired induction is 3.4 N m and the measured torque is 3.6 N m. This represents a relative error of 5.5%. The brake has 60 mm diameter, 39 mm width with a hollow shaft of 12 mm diameter. When exploited up to complete saturation, the measured torque is 5.3 N m with 19 W power consumption. The brake has a torque density of 48.1 kN m−2 and a maximum-to-minimum torque ratio of 176, with 50 ms electromechanical time constant.