Haptic Device With Spherical MR-Brake for Wrist Rehabilitation

This research explored the development of a new haptic device for wrist rehabilitation therapy. Specifically, the therapy requires providing resistive forces against the adduction/abduction, flexion/extension of the wrist and pronation/supination of the forearm. The new haptic device employs a spherical magnetorheological brake (MR-brake). This brake was developed by our research group for a previous study and is the only one of its kind. It resembles a typical ball-joint with 3 degrees of freedom (DOF). It can apply high levels of variable resistive force in a very compact single actuator. The new device was coupled to the spherical MR-brake via linkages so that the virtual center of rotation was placed at the center of the patient’s wrist. Compared to similar devices that use motors, conventional rotary MR-brakes or hybrid MR-motor actuators, our device has the advantage of using just a single compact actuator to control all 3 DOF. The interface is inherently safe in such a rehabilitation application as the MR-brakes are passive devices. Details of the design, the MR-brake and a series of experiments to characterize the device are presented. The experimental results indicate minimal backlash in the linkages and the device can provide easily controllable resistive forces in its range of motion. Such a haptic interface is promising since it can enable a computer-controlled and -monitored rehabilitation therapy with a virtual training environment.Copyright © 2013 by ASME