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,
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