PMA KS 98, Руководство пользователя

Страница: 193 / 246

Controlling the set-point
The digital input
rstart
reacts to a positive signal slope and sets the effective set-point to the process value. The
new goal set-point is started on the basis of the controlled variable xeff .
Such a ramp can only be started with activated gradient function (
Grw
+,
Grw
-,
Grw2
and digital input
gr
_
off
not set). The digital input
w
_
stop
freezes the effective set-point Weff , i.e., the effective set-point is
held to the current value, even if the effective set-point straight approaches a new goal set-point or a new goal
set-point is selected.
Set-point tracking
During the change-over of
Wext r W
it can come to unwanted set-point jumps. To aviod these jumps set-point
tracking exists.
Set-point tracking takes care that in switch-over of
Wext r W
, the past
Wext
is taken over as int. set-point
W
.
When shifting back (
W r Wext
)
Wext
is started with the attitude of
Grw+/-
. If the controller shall follow pro-
cess value or set-point tracking is determined with the configurationword
Wtrac
. Tracking can be activated via in-
terface or digital input
track
.Tracking is evaluated with priority.
a
If in a place (interface or digital input) is switched to tracking, switching in another place is not possible!
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Controller
193 Set-point functions
set-point2
set-point1
Adjustment of
r
set-point1 set-point2
rstart = z
w_stop = 1
w_stop
= 0
gr_off
= 1
upper set-point limit W100
effective set-point
x
W
Time
Set-points, process value
process value
Grw+
lower set-point limit W0
Fig.: 14 Effect of control inputs (
rstart, w-stop
und
gr_off
) on the set-point
set-point2
set-point1
Adjustment of
r
set-point1 set-point2
rstart
=
z
w_stop = 1
w_stop = 0
gr_off = 1
upper set-point limit W100
effective set-point
x
W
Time
Set-points, process value
process value
Grw+
lower set-point limit W0
Fig.: 15 Set-point tracking with switch-over to internal set-point