West Control Solutions Pro-16 - Manual (Page 22)

Operation
9499-040-93811 / 59537-1 Page 22 of 88 Pro-16
During phase 3, heating and cooling are done simultaneously!
3-point-stepping controller
After the start (
1) the controller closes the
actuator ( 2 Out.2). When the difference
between process value and set-point is big
enough (
3), the changing of the process value
is monitored for 1 min. ( 4). Afterwards the
actuator is opened ( 5 Out.1). If the reversal
point is reached ( 6) or there are made enough
measurements, the parameters are detected
and are adopted.
3.8 Help for 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 variable 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
t and x (partial step response) can
be used to determine the maximum rate of increase v
max
.
y = correcting variable
Yh = control range
Tu = delay time (s)
Tg = recovery time (s)
X
max
= maximum process value
V
max
=
t
x
Tg
X
Δ
Δ max
=
= max.
max. rate of increase of process value
The control parameters can be determined from the
values calculated for delay time Tu , maximum rate of
increase v
max
, control range X
h
and characteristic K
according to the formulas given below. Increase Pb, if
stabilized to the set-point oscillates.
Tu
Tg
t
x
y
100%
0%
t
Yh
Xmax
{X
{t
W
X
1min
t
t
1 2 3 4 5 6