Information Technology Reference
In-Depth Information
z
(
t
)=
g
(
z
(
t
)
,u
(
t
))
,
(7)
where
z
(
t
)=[
z
1
(
t
)
,z
2
(
t
)]
T
is the continuous state and
u
(
t
) is the control variable
of the equipment. More specifically, let the dynamics of one piece of equipment
be given by:
z
1
(
t
)=
z
2
(
t
)
,
1
(
t
)
∈
[0
,S
]
(8)
z
2
(
t
)=
u
(
t
)
,
2
(
t
)
∈
[
−
v
max
,v
max
]
,
(
t
)
∈
[
−
u
max
,u
max
]
,
(9)
where
z
1
(
t
)(m)and
z
2
(
t
) (m/s) describe the position and the velocity of equip-
ment, respectively,
u
(
t
)(m/s
2
) represents the acceleration,
S
is the traveling
distance of equipment, [
v
max
,v
max
] is the constraints on
z
2
(
t
), and
u
max
is the
maximum on the acceleration.
−
3 Hierarchical Controller
Based on the decomposed dynamics, the container terminal controller can be
described in terms of two levels in a hierarchical structure (see Fig. 4):
VXSHUYLVRU\FRQWUROOHU
x
i
T
T
T
qc,agv
,4
,1
,3
min
,2
x
i
min
,4
x
i
s
min
,1
s
min
,3
s
min
,6
s
s
min
,5
s
T
T
qc,agv
i
agv,asc
x
T
,6
,5
agv,asc
,2
4&
FRQWUROOHU
$*9
FRQWUROOHU
$6&
FRQWUROOHU
u
z
z
u
z
u
qc
qc
agv
agv
asc
asc
4&
$6&
$*9
Fig. 4.
The hierarchical controller
-
The higher level
In the higher level, the supervisory controller schedules the tasks of each piece
of equipment, or more specifically: the supervisory controller determines at
what time which task should start and how much time is allowed for carry-
ing out that task. In order to schedule the tasks, the higher level needs to
know how much time carrying out each task to be scheduled requires. The
higher level therefore requests from the controllers controlling the dynamics
of the equipment at the lower level the minimal time required for doing a
particular task. Based on this required time received from the lower level
and the discrete-event dynamics, the supervisory controller schedules tasks.
