Burkert Type 8750 - Manual (Page 22)

I
NSTALLATION
20 - 8750
Program function P.CO TUNE (PROCESSTUNE)
To assure good control behaviour, the controller parameters must be adapted optimally to a
controlled member. Good control behaviour is characterized by a short floating time, small
overshoot range and adequate damping.
The process controller of the FMR, together with the positioner, controls as a function of the
pressure difference the flow rate [m³/h] or velocity [m/s] of the medium. The process controller
was preset in the factory with KP = 1; TN → ∞ and TV = 0 (i.e. as a P-controller). With these
parameters, the control does not function!
With the start of the program part P.CO TUNE, the controller parameters fitting the controlled
member are determined by a modified Ziegler/Nichols procedure. For this purpose, under
operating conditions, a single setpoint step is initiated and the response determined. In
evaluation of this response, the program determines automatically the most favourable
controller parameters for the present controlled member. These are transferred to the
program and replace (overwrite) the preset parameters.
Prerequisites for starting P.CO TUNE (PROCESSTUNE)
•
Checking of the factory settings and entry of the process specific parameters have been
completed.
• X.TUNE (AUTOTUNE) has been run successfully through to TUNE-END.
• The entire system is fully operational, i.e. control air, operating voltage, external signals,
medium and any bulk goods to be transported have been activated.
• A process setpoint (setpoint step), which is still to be entered manually, has been
determined (see also the note in the following box).
Preparation for entry of a setpoint step SP
A prerequisite the entry of SP is the activation of the function PROCESSTUNE (P.TUN ON).
Starting point for checking or correction of this setting is the process operating level POS
0, automatic mode, i.e. the yellow LED in key
flashes and the apostrophe (') in the display
runs from left to right.
Press simultaneously the keys and ;
The display now shows P.TUN ON or P.TUN OFF;
With key
, set P.TUN ON and
With key , confirm the correctly set function;
After confirmation the program stands at SP ≡ XXX.X.
SP is the setpoint still to be entered (in m³/h or m/s); it corresponds to the SP-Tune in the box
dealing with the starting value.
The display SP flashes and the apostrophe (') runs from left to right in the display. The 3
horizontal bars ≡ behind SP symbolize the fundamental readiness for starting of
PROCESSTUNE.
NOTE On the „compatibility“ of the external and internal setpoints, and that to
be newly entered.
With the setting SETP EXT, the external setpoint SP is suppressed
when PROCESSTUNE is activated in favour of the setpoint step SP
(SP-Tune) to be newly entered, for the duration of this function. With
the setting SETP INT, the setpoint to be newly entered serves as SP-
Tune for the setpoint step, and after execution of PROCESSTUNE as
the process setpoint SP for subsequent operation in the automatic
mode.