Biomedical Engineering Reference
In-Depth Information
Fig. 10.5
IK and ID steps of the neuromuscular simulation: Computation of the movement with
estimated GRF and muscles activation presented by curves
a
i
=
(
v
i
+
1
−
v
i
)/
t
(10.3)
where
t
denotes the time step.
The force contact point
p
LG
is finally computed by using the moment equation:
M
i
=
F
LG
ⓦ
p
LG
+
m
.
g
ⓦ
p
mc
=
m
i
.
a
i
ⓦ
p
i
(10.4)
i
i
where
p
mc
=
i
m
i
.
m
is the body center of mass.
The output of IK and the computed GRF are used as input in an inverse dynamic
(ID) procedure to compute muscle activation, which are involved in the produced
movement. Finally, the results of the ID step are used in the analysis procedure step
to compute forces acting upon joints. The resulting forces are exported from the
neuromuscular coordinate system to the hip joint coordinate system which is used
in the physically-based simulation.
p
i
/
10.2.3.2 Simulation Model
Aphysical simulationmodel is required to compute the deformation of themechanical
objects. However, different criteria should be taken into account to achieve an
accurate simulation, which faithfully reflects the mechanical behavior of biological
tissues. Indeed, biomechanical constraints such as the nonlinearity, large displace-
ments and deformations of soft tissue have to be considered. Different models based
on mass-spring systems [
24
], the Finite Element Method [
17
] and Finite Volume
Method [
59
] have been proposed to simulate the deformations of soft tissue.
