Robot-aided neurorehabilitation: a robot for wrist rehabilitation

Abstract

In 1991, a novel robot, MIT-MANUS, was introduced to study the potential that robots might assist in and quantify the neuro-rehabilitation of motor function. MIT-MANUS proved an excellent tool for shoulder and elbow rehabilitation in stroke patients, showing in clinical trials a reduction of impairment in movements confined to the exercised joints. This successful proof of principle as to additional targeted and intensive movement treatment prompted a test of robot training examining other limb segments. This paper focuses on a robot for wrist rehabilitation designed to provide three rotational degrees-of-freedom. The first clinical trial of the device will enroll 200 stroke survivors. Ultimately 160 stroke survivors will train with both the proximal shoulder and elbow MIT-MANUS robot, as well as with the novel distal wrist robot, in addition to 40 stroke survivor controls. So far 52 stroke patients have completed the robot training (ongoing protocol). Here, we report on the initial results on 36 of these volunteers. These results demonstrate that further improvement should be expected by adding additional training to other limb segments.

Fig. 1

Planar shoulder-and-elbow robot during clinical trials at Burke Rehabilitation Hospital.

Fig. 2

Wrist robot. Top figure shows a stroke survivor during therapy sessions at Burke Rehabilitation Hospital. Bottom figure shows a solid view of the design.

Fig. 3

Whole-arm robot. The wrist robot can be added to the tip of the planar robot affording five active DOFs (and two passive DOFs) for transport of the arm and manipulation.

Fig. 4

PS motor torque constant as a function of position. The difference in readings at 0° and 360° can be attributed to the experimental variability in the force transducer readings.

Fig. 5

PS motor stability map (the region below the curve is considered stable). Note that the stability conditions apply only to the conditions tested (step size of 50°). The system behaves differently to different sized inputs (a trademark of a nonlinear system). The values of stiffness and damping shown are for the free motor with the pinion and do not represent the stability limits of the assembled system.

Fig. 6

Robot PS stability map. Region under the curve represents the stability region.

Fig. 7

Robot differential stability map (flexion/extension, abduction/adduction and its combinations). Region under the curve represents the stability region.

Fig. 8

Proximal-versus-distal robot training protocol.