Ascon Tecnologic - K31D - OPERATING INSTRUCTIONS - PAG. 8
The
Double Action PID
control algorithm needs the pro-
gramming of the following parameters:
Pb
Proportional Band;
tcr1
Cycle time of the output
1.rEG
;
tcr2
Cycle time of the output
2.rEG
;
Int
Integral Time;
rS
Manual Reset (only if
Int
=
0
);
dEr
Derivative Time;
FuoC
Fuzzy Overshoot Control.
Prat
Power Ratio or relation between power of the element
controlled by output
2.rEG
and power of the element
controlled by output
1.rEG
.
When
Prat
=
0
the output
2.rEG
is disabled and the
control behaves exactly as a
single action PID con-
troller
, through output
1.rEG
.
5.8 Auto-tuning and Self-tuning Functions
All the parameters referring to the
Auto-tuning
and
Self-
tuning
functions are contained in the group
]
rEG
.
The Auto-tuning and Self-tuning functions allow the
auto-
matic tuning
of the
PID variables
.
Auto-tuning function provides the
calculation
of the
PID
parameters
through a
Fast
or
Oscillatory
type tuning cycle,
and, at the end of this operation, the parameters
are stored
in
the instrument memory and
remain constant during control
.
Self-tuning function (rule based “
TUNE-IN
”) instead executes
a
control monitoring
and the
continuous calculation of
the parameters
during control.
Both functions automatically calculate the following parameters:
Pb
Proportional Band;
tcr1
Cycle time of the output
1.rEG
;
Int
Integral Time;
dEr
Derivative Time;
FuoC
Fuzzy Overshoot Control;
and, for the
Double Action PID control
, also:
tcr2
Cycle time of the output
2.rEG
;
Prat
Ratio between
P 2.rEG
/
P 1.rEG
.
5.8.1
How to activate Auto-tuning function
1
Program and activate the desired Set Point;
2
Set parameter
Cont
=
Pid
;
3
If Single Action control, set parameter
Func
according to
the process to be controlled through output
1.rEG
;
4
Program an output as
2.rEG
if the instrument controls the
plant with double action;
5
Program parameter
Auto
as:
1
If
FAST
Auto-tuning is desired to
start automati-
cally
all times the
instrument is switched ON
, on
the condition that the process value is
lower than [
SP
- |
SP
/2|] (when
Func
=
HEAt
) or
higher than [
SP
+ |
SP
/2|] (when
Func
=
CooL
);
2
If
FAST
Auto-tuning is desired to
start automati-
cally
the
next time
the instrument is switched ON,
on the condition that the process value is lower than
[
SP
- |
SP
/2|] (with
Func
=
HEAt
) or higher than
[
SP
+ |
SP
/2|] (with
Func
=
CooL
) and once the tun-
ing is finished, the parameter
Auto
is automatically
switched to the OFF state;
3
If
FAST
Auto-tuning is to be
manually started
se-
lecting the parameter
tune
in the main menu or by
correctly programming the
key as
usrb
=
tune
.
The Auto-tuning starts at the condition that the
PV
is lower than [
SP
- |
SP
/5|] (with
Func
=
HEAt
) or
higher than [
SP
+ |
SP
/5|] (with
Func
=
CooL
);
4
If
FAST
Auto-tuning is desired to
start automati-
cally
all times the
Set Point is changed
or at the
end
of the programmed
Softstart cycle
.
The Auto-tuning starts anyway if
PV
is
lower than [
SP
- |
SP
/5|] (with
Func
=
HEAt
) or
higher than [
SP
+ |
SP
/5|] (with
Func
=
CooL
);
-1
If
OSCILLATORY
Auto-tuning is desired to
start auto-
matically
all times the
instrument is switched ON
;
-2
If
OSCILLATORY
Auto-tuning is desired to
start au-
tomatically
the
next time
the instrument is switched
ON and once the tuning is finished, the parameter
Auto
is automatically switched to the
OFF
state;
-3
If
OSCILLATORY
Auto-tuning is to be
manually
started
using the
key;
-4
If
OSCILLATORY
Auto-tuning is desired to
start
automatically
all times the
Set Point is changed
or at the
end
of the programmed
Softstart cycle
.
Note:
The
Fast
-type Auto-tuning is particularly quick and
shows
no signs of having any effect
on the control
as it calculates the parameters
while reaching the
Set Point
. For the correct execution of the Fast-type
Auto-tuning it is however necessary that at start-up
there is a
certain difference
between
Process Varia-
ble
and
Set Point
. For this reason the instrument only
activates the Fast Auto-tuning when:
–
For
Auto
=
1
/
2
: the Process Value is
lower than [
SP
- |
SP
/2|] (with
Func
=
HEAt
) or
higher than [
SP
+ |
SP
/2|] (with
Func
=
CooL
);
–
For
Auto
=
3
/
4
: the Process Value is
lower than [
SP
- |
SP
/5|] (with
Func
=
HEAt
) or
higher than [
SP
+ |
SP
/5|] (with
Func
=
CooL
).
FAST Auto-tuning is not indicated
when the
Set
Point
is
close
to the
initial reading
or
when
the
variable
measured
varies in an irregular way
dur-
ing the tuning cycle (for reasons due to the process,
the variable rises or decreases).
In these cases it is advisable to use the
Oscilla-
tory
type Auto-tuning which
implements
some
ON/OFF regulation cycles
that make the
process
value oscillate
around the Set Point values that
once finished pass to the PID type control with the
parameters calculated by the Auto-tuning;
6
Exit from the parameter programming;
7
Connect the instrument to the controlled plant;
8
Activate the Autotune process by powering OFF and ON
the instrument if
Auto
=
1
/
2
, or selecting the entry
tunE
in the main menu (or using the
key, when correctly
programmed) if
Auto
=
3
, or changing the Set Point
value if
Auto
=
4
.
At this point the Auto-tuning function is activated and is indi-
cated by the flashing LED
Tun
.
The controller carries out several operations on the connect-
ed plant in order to calculate the most suitable PID param-
eters. If, at Auto-tuning start, the condition for the lower or
higher process value is not found the display will show
ErAt
and the instrument will be swapped to normal control condi-
tions according to the previously programmed parameters.
To make the error
ErAt
disappear, press key
.
The Auto-tuning cycle duration has been limited to 12 hours-
maximum. If Auto-tuning is not completed within 12 hours,
