Biomedical Engineering Reference
In-Depth Information
The robotic part consists of hip, knee, and ankle joints, which independently
performed flexion-extension movements. The bilateral robotic hip joints located
between the bilateral thighs under the perineum moved independently. The
maximal ROM of each joint was hip, 40 degrees; knee, 120 degrees; and ankle,
50 degrees.
The total weight of the robotic part, depending on the length of the upright
strut according to the height of the user, was about 12 kg. The orthotic part was
mostly made of carbon fibers and polypropylene and weighed about 1.5 kg. The
main controller, remote controller, and battery were built into the custom-made
reciprocal walking frame (total weight of the walker, 10 kg). WPAL was designed
to allow the user to stand up and sit down as well to walk with the walking frame.
Safety was a critical challenge in the development of the wearable robot. The
basic safety concept with the WPAL was “to stop when unwanted or accidental
motion occurred”. Additionally, it was equipped with a stop switch of the pull-out
type to enable emergency shut down by the user or others in case of unexpected
motion. When an emergency shutdown occurs, the WPAL assumes a standing
position so that the user will not fall. After an emergency stop, function can be
restarted with the user in a standing position by push-up switch.
Movement patterns of the robotic joint angles in walking were constructed
based on the results of walking of health subjects with orthosis by the three-
dimensional analyzer. A template of combination of joint angles was made from
orthotic walking of healthy volunteers with the Primewalk system. For practical
use, precise adjustment of movement pattern was made in actual trial of each
patient.
In addition, to control the gait mode, an automatic mode and a feedback mode
based on detection of motion of the upper extremities were prepared. The specific
step length and cadence appropriate for the user were decided upon in advance
in the automatic mode, while timing of starting the lower extremity swing and
size of the swing (stride) were determined by sensing the distance of the walker's
movement in the feedback mode (Kagawa, (2007)).
3.4.2 Abilities of WPAL
We introduce WPAL to SCI who were dependent on a wheelchair in daily life and
had experience with Primewalk walking. The subject was male, aged 30 years old.
Spinal cord functional levels was T-12, according to the Impairment Scale of the
American Spinal Cord Injury Association (ASIA AIS) Grade B.
Standing-up, sitting-down and level-ground walking with a reciprocal walk-
ing frame were performed with both the Primewalk and WPAL.
For standing-up and sitting-down, the patient required assistance with Prime-
walk while he was independent in the use of WPAL. Consecutive walking with
WPAL was lasted for 40 min and 580 m. Consecutive walking distance and time
were several-fold longer with WPAL compared with Primewalk.
