Design Considerations for Magnetorheological Brakes

Design considerations for magnetorheological (MR) brakes are discussed for different geometries. A complete modeling in terms of torque density, efficiency, bandwidth, and controllability is presented. The model assigns a desired magnetic flux density over the fluid surface. The magnetic circuit dimensions and the necessary power can be calculated in consequence. The analysis focuses on a single disc and on a single drum brake and highlights the interdependence of the measures of performance as a function of the dimensions. The proposed models have been validated using finite-element analysis, the results demonstrate that both brakes are equivalent in terms of torque density but drum brakes are more reactive and require less power. The analysis has subsequently been extended to multiple-layered brakes with several fluid gaps in parallel. The performance are globally improved by increasing the number of gaps. Finally, the paper considers the influence of the MR fluid characteristics and housing material.