Biomedical Engineering Reference
In-Depth Information
6.1.1 Rehabilitation for Hand Functions
The loss of the hand functions are perceived by the stroke patients as a major
problem and greatly affected their quality of life (QOL) (Broeks
et al
. 1999;
Williams
et al
. 1999), and that the restoration of hand functions are important
to the stroke subjects for their daily living. However, after went through the
upper limb rehabilitation program, most stroke patients recovered some of the
proximal motor functions at the shoulders and elbows but limited recovery for
the distal motor functions at the wrists and hands (Chae
et al
. 2002; Chae and
Hart 2003). As hand functions can do more complex tasks and require more
muscle groups for fine control, the neural representation area at the motor cortex
is larger. It will take longer time and more difficult for patient to retrain the
hand functions. But the rehabilitation of hand functions is still achievable and
under investigation. A few different groups around the world were already
looking into hand rehabilitation using rehabilitation robot. For example, Masia
et al.
developed a hand module for the MIT-Manus which assists the grasping
action (Masia
et al
. 2007). HWARD was a 3-degress of freedom (DOF) robotic
device assists in grasping and releasing movements (Takahashi
et al
. 2005). The
team of Lambercy
et al
. (
chapter 4
) developed the Haptic Knob and HandCARE
to train the wrist pronation/supination and finger flexion/extension (Lambercy
et al
. 2007; Dovat
et al
. 2007). Kawasaki
et al
. built a 18-DOF hand motion assist
robot (Kawasaki
et al
. 2007). A novel hand rehabilitation robot for hand functions
training was developed as the extension of training for the upper extremities after
the PolyJBot (
Chapter 5
).
6.2 DESIGN OF THE HAND REHABILITATION ROBOT
The hand rehabilitation robot is designed to train the hand functional tasks such
as hand opening and hand grasp (i.e. palmar grasp and pinch). Each individual
finger is powered by a separate actuator. This design requirement allows more
complex pattern or task can be implemented. Hence a suitable actuator has to be
found first. A few different actuators had been considered such as the voice coil
motor, servo motor and linear actuator. However, the linear actuator was chosen
because it can directly actuate the finger without the need to use gears or cable
to transmit the power. And the micro linear actuator (ie. model L12) from the
Firgelli, Canada meets our requirements with its small size, low cost and light
weight characteristics.
According to Boissy
et al
., the average grip force for the affected hand for stroke
patient was about 130 N (Boissy
et al
. 1999). Comparing with other robot hand
designs, maximum regulated output force for HWARD is 4-15N (Cramer
et al
.
2007) while it was 16 N for Rutger Master Hand II (Bouzit
et al
. 2002) and 15N for
HandCare (Chapter 4.3.2
)
. Therefore, the L12 linear actuator with 100 mm stroke
length and 50:1 gear ratio would provide adequate speed (23 mm/s) and force
(12 N) for assisting finger movement for stroke patient.
