Biomedical Engineering Reference
In-Depth Information
and closing of the hand, and a rotational DOF provides pronation and supina-
tion around the long axis of the forearm. The HapticKnob uses two moving
parallelograms similar to an umbrella, on which the user places the fingers (
Fig.
tionally relevant grips such as power grasp, precision grip or lateral pinch. The
device can generate forces of up to 50 N in both opening and closing directions
and torques of up to 1.5 Nm in pronation and supination.
Four force sensors are incorporated into the structure to measure grasping
forces of up to 30 N applied by the subject. Various force effects can be imple-
mented, e.g. to resist or assist movement as a function of the user's impairment
in an assist-as-needed manner. This robot has dimensions of 60
25 cm
3
and
can easily be transported and set up in minimal time. Further information on the
HapticKnob can be found in (Lambercy
et al.
(2007)).
×
30
×
4.3.2 The HandCARE
The HandCARE is a cable driven robotic device, where each fingertip is attached to
a cable loop, connected to a single motor, allowing predominantly linear displace-
ment corresponding to finger flexion/extension
(
Fig. 4.3(F)
)
. The interface can thus
assist the subject in hand opening and closing movements. Instead of using five
actuators, a clutch system has been developed, which simplifies the control of the
robotic device and reduces the cost. The clutch allows switching between three
modes, (i) active, where the torque generated by the motor is transmitted to the
finger, (ii) fixed, where no finger movement is possible and force control can be
trained isometrically, and (iii) free, where the finger can be moved freely along
the path of the cable. This clutch system makes training of different movements
possible with only one actuator and one clutch per finger. It is thus possible to train
grasping and precision grip as well as fractionation, i.e. independent movement
or isometric force training of each finger, thereby increasing strength in individual
muscles and coordination between fingers.
The active workspace consists of five linear paths of 8 cm length corresponding
to a finger extension/flexion angle range of 0
70
◦
at the metacarpophalangeal
(MCP) joint. The maximal continuous force that can be generated in flexion or
extension is 15 N per finger (up to 75 N if only one finger is actuated), while
inherent friction is less than 0.8 N in any position of the workspace. Forces
applied at the fingertips during the exercises can be recorded by a sensing system
measuring the tension in the cable attached to each finger. Further information on
the HandCARE can be found in (Dovat
et al.
(2008)).
−
4.3.3 Rehabilitation Exercises and Strategies
Robotic devices offer a large number of new modalities for the treatment of
stroke patients, but interactive, motivating and task oriented exercise programs
are critical for subjects to use a rehabilitation robot to its full potential. We review
