West Control Solutions KS 42-1 - Manual (Page 17)

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
control 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 para-
meters.
Three-point controller
The parameters for heating and coo-
ling are determined in two attempts.
The heating power is switched on
(1). At reversal point 1, heating para-
meters
Pb1, ti1, td1 and t1
are determined. The process value is
lined out to the set-point (2). The
cooling power is switched on (3). At
reversal point 2, parameters
Pb2, ti2, td2 and t2 are determined and the
self-tuning attempt is finished. Control to set-point W is using the new parame-
ters.
3.6 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
.
Operation
Operating KS4x-1 17 Manual tuning
t
+100%
Y 0%
-100%
X
W
t reversal point 1
t reversal point 2 start r 1 2 3
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
2
100%
Y
0%
X
W
start r 1 3 t reversal point
blinks