IEEE Robotics & Automation Magazine - March 2023 - 66

to train active hand grasping and opening (i.e., releasing). To
encompass a variety of hand sizes, the distance and orientation
of the thumb module relative to the user's palm are adjustable
by linear joint 1 (LJ1) and LJ3 (as shown in Figure 4), while
the four-finger module allows variable distances between the
metacarpophalangeal (MCP) and proximal interphalangeal
(PIP) joints (LJ2 in Figure 4). Both pieces can be adjusted for
fit and comfort while the user is wearing the device.
Both the thumb and four-finger modules have RJs with a
torsion spring (RJ1, RJ2, RJ3, and RJ4 in Figure 4) to help the
active opening of the hand. Force-sensitive resistors (FSRs)
are placed underneath plastic pads, where the thumb and fingers
contact, to measure the relative pressure that occurs when
the hand is opened or closed.
This pressure is used to measure functional aspects of the
thumb and fingers and can also be used in concert with the
torsion springs to estimate the finger position. In the thumb,
two orthogonal sensors are used to detect the relative magnitudes
of thumb force in each of two directions: 1) in the
flexion/extension direction and 2) in the opposition/reposition
direction. The latter is helpful in monitoring the level of
undesired tone present in thumb adduction. Thumb mobility is
supported by a passive single-DoF flexion/extension axis (RJ3
in Figure 4) and a movable and lockable opposition/reposition
adjustment described in [12]. The FSR pressure sensors were
successfully evaluated to determine the pressure applied by
the thumb and the four-finger modules independently [12].
The algorithm developed to process the FSR sensor data provides
the quantity of pressure applied by the user, where 0% is
an open hand and 100% is a completely closed hand. A strap
with soft foam is used to secure the hand and prevent unexpected
doffing of the module.
TELEREHABILITATION PLATFORM
Therapy with AA is carried out in conjunction with a telerehabilitation
platform based on serious games. This platform comprises
eight games for the assessment and 10 serious games for
the training. Games have been designed to be easy to use and
understand with the aim of supporting remote supervision by a
therapist. Developed in collaboration with therapists and end
users, the games are highly motivating to increase the user's
voluntary engagement in training [16]. Additionally, they allow
Arc Piece
Arc Piece
With Teeth
Plate for Hand
Module Assembly
Plastic Cover
Potentiometer
With Gear
Base Assembly
Pins
Inner Bar
Inner Bar
Outer Bar
Plate for Pins
Screw
Spring
(a)
Forearm Bar
Outer Bar
Holes
Pin
Pin
(b)
(c)
FIGURE 3. A wrist module. (a) The structure and core components. (b) and (c) An illustration of a one-button release mechanism.
Thanks to rounded holes in the inner bar and spring, two pins of the module are simply inserted into two holes in the inner bar and then
automatically locked [red circle in (b)]. Pushing the inner bar [shown in (c)] aligns the holes in the inner bar with those in the outer bar
[red circle in (c)], resulting in quick and easy release. The movement of the inner bar is constrained by a screw (orange circles).
66 IEEE ROBOTICS & AUTOMATION MAGAZINE MARCH 2023
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IEEE Robotics & Automation Magazine - March 2023

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