A Wearable Exoskeletal Rehabilitation Robot for Interactive Therapy - Biomechatronics in Medicine and Healthcare - page 12

2.3 REVIEW OF REHABILITATION ROBOTS FOR THE
UPPER-EXTREMITY

Ever since the first report about the MIT MANUS therapy robot (Krebs et al.
(1998)), there has been an explosive growth in the number of robotic devices
developed for the therapeutic training of the upper-extremity. The earlier devices
had mainly focused on training simple reaching movements that use the shoulder
and elbow joints. However, the later ones had incorporated additional degrees-of-
freedom (DOFs) in the robotic structure to include the training of the wrist/hand
as well; there are also devices that are purely used for training the hand and the
wrist. Each of these devices varies in terms of the exact mechanical design of
the robot, the number of DOFs, the type of actuators and instrumentation used
in these devices, and the types of movements supported by the robot etc. These
rehabilitation robots can be classified into different types based on their interaction
with user, and their engineering details. One of the possible schemes for classifying
these devices was proposed by (Micera et al. (2005a)). We have added an extra
category to this (Micera et al. (2005a)) classification scheme to make it more
general ( Table 2.1 ), which results in a scheme with two levels of classification -
the first level is based on the nature of the mechanical structure of the robot, which
differentiates rehabilitation robots into two major categories,

• Operational machines - These are robotic devices with an end-effector that

is in physical contact with either the subject's hand or the forearm. The
distal part of the upper-extremity is the only part of the subject's body that
is in contact with the robot. This means that the subject is free to utilize
their own joint movements to execute the tasks that are programmed in
the operational space of the robot. These devices are also relatively easy to
design and implement, as the mechanical structure of the device is mostly
unaffected by the mechanical structure of the subject's upper-extremity.
The only requirement for these devices is that they should have enough
DOFs to sufficiently cover the subject's workspace for training different
types of movements. Additionally, these devices can be operated by users
either with their right or left arm, without requiring any change to the
device.

Tab l e 2 . 1 Classification of Rehabilitation Robots.

DOF Control a Category Backdrivabe Complexity Cost

Operational Class I No Yes High Moderate

Operational Class II No No Low Low

Exoskeleton I Yes Yes High High

Exoskeleton II b Yes No Moderate Low

a This indicates if the different DOFs of a human UE can be controlled independently by the robot.
b This is the additional category not included in the (Micera et al. (2005a)) classification scheme.