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focus. Time-ecient traction strategy is aimed at running at the whole section in
the shortest possible time with the most traction and braking capacity [5,6]. An
optimization method that the factors, such as speed limit, track alignment, and
running time, are taken into account. A simulated annealing algorithm(SA) is
developed to search for optimal coasting point. The developed model is applied
to a particular segment of route in Shanghai. Experiment results demonstrate
that, although there was a mite increase of running time, the method could
effectively reduce energy consumption.
2 Energy Consumption
The total consumed energy for a train movement consists of traction energy
and brake energy. In the Communication Based Train Control(CBTC) System,
traction and brake systems receive command and amount of traction and brake
from the on-board Automatic Train Controller (ATC) to produce the energy
consumption. Fig. 1 describes the train traction characteristic in the overload
situation.
The motion of a train is determined by the difference between tractive effort
F
traction
and running resistance
F
resistance
.
F
resistance
is a comprehensive resis-
tance of a variety of resistance, including basic and additional resistance by its
formation.
Basic resistance always exists in train movement. The acceleration of basic
resistance can be determined by (1)
a
ω
0
=
a
+
bv
+
cv
2
.
(1)
where
v
is train speed; and a, b, c are basic resistance parameters, determined
by operation conditions and train composition.
Additional resistance consists of ramp resistance, curve resistance and tunnel
resistance, acceleration respectively:
a
ω
i
=
[
i
1
×
l
+
i
2
×
(
L
−
l
)]
g
.
(2)
10
3
L
where
i
1
,
i
2
is track gradient; L is train length; l is the segment length of train
on the
i
1
ramp.
a
ω
r
=[
600
l
+
600
g
10
3
L
.
R
1
×
R
2
×
(
L
−
l
)]
(3)
where
R
1
,
R
2
is curve radius; L is train length; l is the segment length of train
on the
R
1
curve.
L
s
v
2
g
10
10
a
ω
s
=
3
.
6
2
.
(4)
×
where
L
s
is the tunnel length;
v
is train speed in the tunnel.
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