48/57 CC1B7865en 05.12.2002 HVAC Products
9. Self-setting function
F
«tunE» is only possible in high-fire operation, in the «modulating burner» mode.
The self-setting function «tunE» is a proper software function unit that is integrated into
the controller. In the «modulating» mode, «tunE» tests the response of the controlled
system to steps of the positioning 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 any number of times.
Self-setting Start
Identification of
the controlled
system
PID controller
settings
Controller
Controlled
system
Y
W
X
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The «tunE» function uses 2 different methods that are automatically selected
depending on the dynamic state of the actual value and the deviation from the setpoint
at the start. «tunE» can be started from within any dynamic actual value sequence.
If there is a large difference between actual value and setpoint when «tunE» is
activated, a switching line is established about which the controlled variable performs
forced oscillations during the self-setting procedure. The switching line is set at such a
level that the actual value should not exceed the setpoint.
Switching
level
w
x
Start
t
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With a small deviation between setpoint and actual value (after the controlled system
has stabilized, for instance), a forced oscillation is performed about the setpoint.
9.1 Self-setting function in high-fire operation
2 procedures
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