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In this paper, our case study is restricted to a few design parameters and focuses on
the equilibrium requirement for the power lift gate. The design parameters are
X =
[
x
MB
, y
MB
, x
NL
, y
NL
] i.e. the 2D coordinates of the electric cylinder fixation points
M
(on the car body) and
N
(on the lift gate). The equilibrium requirement is related to
four constraints previously identified in the analysis based on SysML:
C
Δ
F
: “The additional force value
F
required to maintain the lift gate static equilib-
rium is inferior to some threshold level
(
Δ
Δ
F
max
)”.
Δ
F
refers here to the force
Δ
F
de-
fined as
F
cyl
= F
spring
+
F
, where
F
cyl
is the cylinder force required to maintain the
static equilibrium and where
F
spring
is the force of the spring within the power cylinder
used to reduce the power of the electrical motor;
C
L
: “The electric cylinder length
L
is within the interval [
L
min
, L
max
] related to the
aperture angle of the lift gate”;
C
M
: “The car body fixation point
M
is within a specified area”;
C
N
: “The lift gate fixation point
N
is within a specified area”.
Following formal computations guided using causal ordering techniques, all the con-
straints are expressed as functions of the design parameters, and the text file required
as input of the interval CSP solver is so obtained. The preliminary design of the
power lift gate then consists in using the interval solver outputs to understand the
influence of the opening angle on the position of fixation points and to perform a
(possibly iterative) refinement by selecting an area in the solution space.
Δ
(
a
)
θ=0°
(
c
)
θ=0°
(
b
)
θ=0°
(
d
)
=
(
a
)∩(
b
)∩(
c
)
(
f
)
N
in (
x
NL
,
y
NL
)
(
e
)
M
in (
x
MB
,
y
MB
)
Fig. 12.
Interval CSP outputs (a to f)
Fig. 12 (a-d) illustrates the influence of the opening angle on the solution set. This
corresponds to a preliminary study before an exhaustive search for all the opening
angles. Focusing on an area in the search space corresponds to the refinement related
to the preliminary design process. The reduced search area allows a more precise
exploration while preserving a reasonable computation time. The proposed refinement
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