Compact MR-brake with serpentine flux path for haptics applications

This research explores a new approach to shape the magnetic flux path in a MR brake. Magnetically conductive and non-conductive elements were stacked to weave the magnetic flux through the rotor and the outer shell of the brake. This approach enabled design of a more compact and powerful MR brake. In addition, a ferro-fluidic sealing technique was developed to prevent the fluid from leaking and to reduce off-state friction. Experimental results showed that, when compared to a commercial MR brake, our 33% smaller prototype MR-brake could generate 2.7 times more torque (10.9 Nm). A 1-DOF haptic interface employing the brake enabled crisp virtual wall collision simulations. Significant reduction in the off-state torque was obtained by applying a reverse current pulse to collapse a residual magnetic field in the brake.