Possibilities For Optimization - Siemens SIMATIC S7-1200 Function Manual

Using PID basic functions
7.3 TCONT_CP
7.3.3.3

Possibilities for optimization

The following possibilities for tuning exist:
● Pretuning
● Fine tuning
● Manual fine-tuning in control mode
Pretuning
During this tuning, the working point is approached from the cold state through a setpoint
jump.
With TUN_ON = TRUE, you can establish the tuning readiness. The controller switches from
PHASE = 0 to PHASE = 1.
The tuning manipulated variable (LMN0 + TUN_DLMN) is activated by a setpoint change
(transition phase 1 -> 2). The setpoint is not effective until the inflection point has been
reached (automatic mode is not enabled until this point is reached).
The user is responsible for defining the output excitation delta (TUN_DLMN) according to the
permitted process value change. The sign of TUN_DLMN must be set depending on the
intended process value change (take into account the direction in which the control is
operating).
The setpoint step change and TUN_DLMN must be suitably matched. If the value of
TUN_DLMN is too high, there is a risk that the point of inflection will not be found before 75%
of the setpoint step change is reached.
TUN_DLMN must nonetheless be high enough to ensure that the process value reaches at
least 22 % of the setpoint step change. Otherwise, the process will remain in tuning mode
(phase 2).
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Function Manual, 03/2017, A5E35300227-AC
PID control