Biomedical Engineering Reference
In-Depth Information
Figure 7.2
An anatomical segment showing the GRS, the marker axes, and anatomical
axes. Three tracking markers,
m
T
1
,
m
T
2
,and
m
T
3
, in conjunction with two calibration
markers,
m
C
1
and
m
C
2
, define the constant [M to A] matrix. The three tracking markers
in the GRS define the [G to M] matrix. The product of the variable [G to M] and the
fixed [M to A] matrices gives the variable [G to A] matrix from which a new
θ
1
,
θ
2
,
and
θ
3
are defined for each frame.
the leg segment the three tracking markers could be placed on the head of
the fibula
(m
T
3
)
, on the lateral malleolus
(m
T
2
)
, and at the midpoint on the
anterior surface of the tibia
(m
T
1
)
. During calibration, temporary markers,
m
C
1
and
m
C
2
, could be placed on the medial malleolus and the medial epi-
condyle of the tibia, respectively. With the subject standing still for about a
second, the coordinates of the three tracking and the two calibration markers
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