Manual Tuning; Autotuning - gefran GFX4 Configuration And Programming Manual

MANUAL TUNING

A) Enter the setpoint at its working value.
B) Set the proportional band at 0.1% (with on-off type setting).
C) Switch to automatic and observe the behavior of the vari-
able. It will be similar to that in the figure:
D) The PID parameters are calculated as follows: Proportional
band
Peak
P.B.= ---------------------------------------- x 100
V max - V min
(V max - V min) is the scale range.
Integral time It = 1,5 x T
Derivative time dt = It/4
E) Switch the controller to manual, set the calculated param-
eters (activate the PID control by setting a cycle time for relay
outputs, if any), switch to automatic.
F) To assess parameter optimization, change the setpoint
value if possible and check temporary behavior. If oscilla-
tion persists, increase the value of the proportional band; if
response is too slow, decrease the value.

AUTOTUNING

Enabling the autotuning function blocks the settings of the PID parameters.
Autotuning continues to measure the system oscillations, seeking as quickly as possible the PID parameter values
that reduce the oscillation; it does not intervene if the oscillations drop to values below 1.0% of the proportional band.
It is interrupted if the setpoint is changed, and resumes automatically with a constant setpoint. The calculated parameters are not
saved; if the instrument is switched off the controller resumes with the parameters programmed before autotuning was enabled.
Autotuning terminates the procedures with switching to manual.
Enabling the autotuning function blocks the settings of the PID parameters.
It can be two types: continuous or one shot.
Continuous autotunìng is enabled with parameter Stu (values 1, 3, 5); it continues to measure the system oscillations,
seeking as quickly as possible the PID parameter values that reduce the oscillation; it does not intervene if the oscillations
drop to values below 1.0% of the proportional band.
It is interrupted if the setpoint is changed, and resumes automatically with a constant setpoint.
The calculated parameters are not saved if the instrument is switched off, in case of switching to manual or disabling the code
in configuration, and controller resumes with the parameters programmed before autotuning was enabled.
The calculated parameters are saved when the function is enabled via digital input or via A/M key (start /stop) at stop.
One-shot autotuning can be activated manually or automatically with parameter Stu (as can be seen on the table,
the values to be set depend on enabling of Selftuning or Softstart).
It is useful for calculating PID parameters when the system is in the vicinity of the setpoint; it produces a variation on the control
output of a maximum of ± 100% of the current control power limited by h.PH - h.PL (heat), c.PH - c.PL (cool) and assesses
the effects in overshoot over time. The calculated parameters are saved.
Manual activation (code Stu = 8, 10, 12) by setting the parameter directly or via digital input or key.
Automatic activation (code Stu = 24, 26, 28 with error range of 0.5%) when the PV-SP error exceeds the defined range
(programmable at 0.5%, 1%, 2%, 4% of full scale).
Activation is inhibited if PV <5% or PV >95% of input scale.
NB: at switch-on after selftuning, after switching to MANUAL, after software shutdown or after a setpoint change, automatic
activation is inhibited for an interval equal to five times the integral time, with a minimum of 5 minutes.
An identical interval has to lapse after a one-shot run.
48
Process
variable
Peak
See: CONTROL - PID Parameters
See: CONTROL - PID Parameters
880397M_MSW_GFX4-GFXTERMO4_08-2018_ENG
T
Time