Siemens SIMATIC Manual page 19

GAIN * D_F ER
Integrator (TI, I_ITL_ON, I_ITLVAL)
In the manual mode, it is corrected as follows: LMN_I = LMN - LMN_P - DISV.
If the manipulated variable is limited, the I-action is stopped. If the error moves the
I-action back in the direction of the manipulated variable range, the I-action is
enabled again.
The I-action is also modified by the following measures:
•
The I-action of the controller is deactivated by TI = 0.0
•
Weakening the P-action when setpoint changes occur
•
Control zone
•
Online modification of the manipulated value limits
Weakening the P-Action when Setpoint Changes Occur (PFAC_SP)
To prevent overshoot, you can weaken the P-action using the "proportional factor
for setpoint changes" parameter (PFAC_SP). Using PFAC_SP, you can select
continuously between 0.0 and 1.0 to decide the effect of the P-action when the
setpoint changes:
•
PFAC_SP=1.0: P-action has full effect if the setpoint changes
•
PFAC_SP=0.0: P-action has no effect if the setpoint changes
The weakening of the P-action is achieved by compensating the I-action.
Derivative action element (TD, D_F)
•
The D-action of the controller is deactivated with TD = 0.0.
•
If the D-action is active, the following relationship should apply:
TD ≥ 0.5 * CYCLE * D_F
PID Temperature Control
A5E00125039-02
Continuous Temperature Controller FB 58 "TCONT_CP"
ER
LMN_Sum
*
TD / D_F
TI
LMN_Sum(t)
GAIN * ER (0)
GAIN * ER (0)
ER (t)
t
2-5