Biomedical Engineering Reference
In-Depth Information
For example, if we choose sequence Z,X
′
,Y
″
proposed to
analyze the movement of knee joints (GRO 83], the first
rotation occurs about axis Z
i-1
attached to the upstream or
proximal
segment
(thigh)
and
corresponds
to
flexion/extension (denoted as
), the third rotation
occurs about axis Y
i
attached to the downstream or
distal
α
segment
(shank)
and
corresponds
to
the
internal/external rotation (denoted as
), and finally the
intermediate rotation occurs about the floating axis X,
perpendicular to Z
i-1
and Y
i
and corresponds to the
varus/valgus (denoted as
γ
).
β
floating axis
Figure 3.4.
Illustration of the rotation sequence Z, X
′
,Y
″
−
R
is in this case obtained
by multiplying the matrices expressing the elementary
rotations about each axis, in the order of that in the selected
sequence.
The overall rotation matrix
i
1
,Z
,X
,Y
→
→
