Page 45 - Mechatronics for Safety, Security and Dependability in a New Era

Ch07-I044963.fm Page 29 Tuesday, August 1, 2006 12:30 PM
Page 29
Tuesday, August 1,2006
12:30 PM
Ch07-I044963.fm
29 29
stance phase and the swing phase. The peak of the load applied to the circumference of the ankle
joint in the stance phase in normal gait was 28kgf of ankle Dorsiflexion; on the other hand, the peak
of the load in the spastic gait was 8kgf of ankle dorsiflexion. The load by ankle plantarflexion was
about -3kgf of the position where the swing phase and stance phase change; on the other hand, the
spastic gait was about -31kgf in swing phase. Fig.3 shows the moment of the circumference of the
ankle joint when using the orthosis for this experiment and a motion capture system. In the motion
capture system, the moment is calculated from the ankle joint position of a reflective marker and the
floor reaction force. Using the orthosis in the experiment, the moment is calculated from the ankle
joint position of the orthosis and the force measured by the load-cell. Since there is no floor
reaction-force data during the swing phase in the force platform, the moment of this phase is not
calculated. The normal gait shows that the foot enters the stance phase from the heel strike; on the
spastic gait, the foot enters from a foot-flat by a drop foot tendency. The difference between the
normal gait and spastic gait is clearly shown in a comparison.
Experiment of Spastic rty
Load (kgf)
(Spasticity gait)

-20
Tirrefe) Time (s)
Figure2: The load of SMO

Time(s) Time(s)
Figure3: The result of VICON and SMO

Discussion

Fig.4 shows a comparison of the force in the circumference of the ankle during gait and the gait
cycle. The relationship between each event in the gait and the force in the circumference of an ankle
is as follows:
1: Acceleration begins as soon as the foot leaves the ground, and at this time, the force of kicking the
ground causes the ankle plantarflexion.
2: Midswing occurs when the foot passes directly beneath the body, and in order to shake out the
foot, the force causes the ankle dorsiflexion.
3: Deceleration stabilizes the foot in preparation for the next heel strike, and the force causes the
ankle plantarflexion.