If the range of the manipulated variable is reduced and the new unlimited value of the
manipulated variable is outside the limits, the I-action and therefore the value of the
manipulated variable shifts. The manipulated variable is reduced by the same amount as
the manipulated variable limit changed. If the manipulated variable was unlimited prior to
the change, it is set exactly to the new limit (described here for the upper manipulated
variable limit).
n The LMN_NORM function normalizes the manipulated variable according to the fol-
lowing formula:
LMN = LmnN * LMN_FAC + LMN_OFFS
n It can be used for the following purposes:
Manipulated variable adaptation with LMN_FAC as manipulated variable factor and
LMN_OFFS manipulated variable offset
n The value of the manipulated variable is also available in the peripheral format. The
CRP_OUT function converts the LMN floating-point value to a peripheral value
according to the following formula:
LMN_PER = LMN * 27648/100
With the default values (LMN_FAC = 1.0 and LMN_OFFS = 0.0), normalization is dis-
abled. The effective manipulated variable is output at output LMN.
The schematic below shows the block diagram:
If the current parameter settings are usable, you can save them in a special structure in
the instance DB of FB 58 TCONT_CP prior to making a manual change. If you tune the
controller, the saved parameters are overwritten by the values that were valid prior to
tuning. PFAC_SP, GAIN, TI, TD, D_F, CONZ_ON and CON_ZONE are written to the
PAR_SAVE structure.
The last controller parameter settings you saved can be activated for the controller again
using this function (in manual mode only).
Following tuning, the PI and PID parameters are stored in the PI_CON and PID_CON
structures. Depending on PID_ON, you can use LOAD_PID in the manual mode to write
the PI or PID parameters to the effective controller parameters.
PID parameter PID_ON = TRUE PI parameter PID_ON = FALSE
GAIN = PID_CON.GAIN GAIN = PI_CON.GAIN
TI = PID_CON.TI TI = PI_CON.TI
TD = PID_CON.TD
Changing the Manipulated
Variable Limits Online
Manipulated Variable Nor-
malization LMN_NORM
(LMN_FAC, LMN_OFFS)
Saving and Reloading
Controller Parameters
Saving Controller Parame-
ters SAVE_PAR
Reloading Saved Con-
troller Parameters
UNDO_PAR
Changing Between PI and
PID Parameters LOAD_PID
(PID_ON)
VIPA SPEED7
Standard
PID Control > FB 58 - TCONT_CP - Continuous Temperature Control
HB00 | OPL_SP7 | Operation list | en | 18-30 870
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