This research explored design of a magnetorheological (MR) spherical brake as a multi-DOF actuator. To the best of our knowledge, our design is the first ever multi-DOF spherical brake using MR fluid. The primary goal was to design a compact but powerful brake using the serpentine flux path approach. An optical position measurement system was also designed to eliminate the gimbal mechanisms that are typically used in spherical joints for position measurement. It was found that the braking torque scales up proportionally to the cube of the brake radius.

A prototype spherical brake was built with 76.2 mm diameter and 3.7 Nm braking torque.

A joystick was built as a haptic device using the MR spherical brake. Virtual wall collision experiments showed crisp reaction force at initial contact and very high rigidity during the contact.

Publication

• Spherical brake with MR fluid as a multi degree of freedom actuator for haptics,” Journal of Intelligent Material Systems and Structures, vol. 20, pp. 2149-2160, December 2009.