User's Manual

Document MV0319P.N
© Xsens Technologies B.V.
MVN User Manual
119
19.7.10 Foot (Calcaneus): Segment 18 Right and Segment 22 Left
MVN
ISB
[ii]
O
jRightAnkle
jLeftAnkle
IM
IM
X
Sagittal plane forward
Line perp. to frontal plane of tib/fib
in neutral configuration.
Pointing anteriorly.
Y
Vertical (aligned with gravity,
pointing up)
Line coincident with long axis of
tibia/fibula, in neutral configuration.
Pointing cranially
Z
Perp. to X and Y
Pointing right
Line perp. to x- and Y-
Note: In the MVN model lateral and medial malleoli are on the same height.
19.7.11 Toe: Segment 19 Right and Segment 23 Left
The toes are not defined in ISB.
MVN
ISB
O
jRightToe
jLeftToe
The toes are not defined in ISB.
X
Sagittal plane forward
Y
Vertical (aligned with gravity)
Z
Perp. to X and Y
Note: In MVN toes are not measured directly but are based on the foot kinematics and contact detection.
The origin is between the metatarsals of the foot. Toes can only flex and extend, other kinematics are
due to interpolation.
19.8 Joint angles
Typically, a joint rotation is defined as the orientation of a distal segment
B
GB
q
with respect to a proximal
segment :
A B A B
B B GB GB
*
q= q q
where

denotes a quaternion multiplication and
*
the complex conjugate of the quaternion (see
Section 19.3.1). There are a few commonly used parameterizations of the joint rotation
AB
BB
q
that
describe joint angles:
 the Cardan/Euler representation [Cole 1993, Woltring 1994]
 joint coordinate system [Grood & Suntay 1983]
vi
 helical angle [Kinzel 1972]
A
GB
q