West Control Solutions D280-1 - Manual (Page 20)

Start: heating power switched off
The controller waits 1,5 minutes (1).
Heating power Y is switched on (2).
At the reversal point, the self-tuning at-
tempt is finished and control to the
set-point is using the new parameters.
Start: at set-point
Heating power Y is switched off (1).
If the change of process value X was
constant during one minute and the con-
trol deviation is > 10% of
SP.Hi -
SP.LO (2), the power is switched on
(3). At the reversal point, the self-tu-
ning attempt is finished, and control to
set-point W is using the
new parameters.
4.4 Manual tuning
The optimization aid should be used with units on which the control parameters
shall be set without self-tuning.
For this, the response of process variable x after a step change of correcting va-
riable y can be used. Frequently, plotting the complete response curve (0 to
100%) is not possible, because the process must be kept within defined limits.
Values T
g
and x
max
(step change from 0 to 100 %) or
Dt and Dx (partial step re-
sponse) can be used to determine the maximum rate of increase v
max
.
Controller
Digital 280-1 Manual tuning 20
t
2
100%
Y
0%
X
W
start r
1 3 t turning point
blinks lit off
Tu
Tg
t
x
y
100%
0%
t
Yh
Xmax
{X
{t
y = correcting variable
Y
h
= control range
Tu = delay time (s)
Tg = recovery time (s)
X
max
= maximum process value
V
max
=
Xmax
Tg
=
{
{
x
t
= max. rate of
increase of process value
t
100%
Y
0%
X
W
start r
1 2 t turning point
blinks lit off