Tune" Function - Siemens RWF40 Installation, Use And Maintenance Instructions

"tunE" FUNCTION

The RWF40 controller has a self-tuning or self-acquisition function of the setting parameters "tunE".
This function allows the controller to autonomously acquire the necessary parameters (Pb1 - rt - dt etc) for controlling and setting up the process.
For the self-tuning to work correctly, it is important that the process is not subject to sudden oscillations or instability, and neither remains at the
constant value without any variation, furthermore there must be no boilers in parallel.
Note. "tunE" is only possible in high-fire operation, in the "modulating burner" mode.
Self-tuning
Start self-tuning with
PGM
Cancel with
When "tunE" stops flashing, self-tuning has
stopped.
Accept the parameters that have been determined by pressing
for at least 2 s!)
Note. It is not possible to start "tunE" in manual operation or thermostat operation.
Self-tuning function in high-fire operation
The self-tuning function "tunE" is a pure software func-
tion unit that is integrated into the controller.
In the "modulating" mode of operation, "tunE" tests the
response of the controlled system after variations of the
position signal according to a special procedure. A
complex control algorithm uses the response of the
controlled system (actual value) to calculate and store
the control parameters for a PID or PI controller (set dt
= 0!).
The "tunE" procedure can be repeated as often as re-
quired.
Two procedures
The "tunE" function uses two different methods that
are automatically selected depending on the dynamic
state of the actual value and the difference from the set-
point at the start. "tunE" can be started from within any
dynamic actual value sequence.
X
Start
W
X
Start
W
+
Switching
level
(press the button
Self-tuning
PID controller
settings
W
Controller
–
X
If there is a large difference between actual value and
setpoint when "tunE" is activated, a switching line is estab-
lished around which the controlled variable performs forced
oscillations during the self-tuning procedure. The switching
line is set at such a level that the actual value should not ex-
ceed the setpoint.
With a small deviation between setpoint and actual value,
for instance when the controlled system is stabilized, a
forced oscillation is performed around the setpoint.
The controlled system data which are recorded for the
t
forced oscillations are used to calculate the controller pa-
rameters "rt, dt, Pb.1" and a filter time constant for actual
value filtering that is optimized for this controlled system.
Conditions
• The thermostat function (relay 1) must be constantly acti-
vated, otherwise "tunE" is interrupted and no optimised
controller parameters are acquired.
• The above-mentioned actual value oscillations during self-
tuning may not exceed the upper threshold of the thermo-
stat function (increase if necessary, and lower the set-
point).
t
44
+
PGM
223.8
tunE
Start
Identification of
the controlled
system
Controlled
system
Y