Controller Tuning In Fb 58 "Tcont_Cp; Introduction - Siemens SIMATIC Manual

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Controller Tuning in FB 58 "TCONT_CP"

3.1

Introduction

The controller optimization is to be used exclusively for heating or cooling
processes.
With controller tuning in FB 58 "TCONT_CP", the PI/PID controller parameters are
set automatically. There are two ways of tuning:
•
Tuning by approaching the operating point with a setpoint step change
•
Tuning at the operating point by setting a start bit
In both cases, the process is excited by a selectable manipulated variable step
change. After detecting a point of inflection, the PI/PID controller parameters are
available and the controller switches to automatic mode and continues to control
with these parameters.
You can also tune your controller using the wizard in the parameter assignment
user interface.
Optimizing the Controller Response
The controller design is intended for an optimum response to disturbances. The
resulting "sharp" parameters would lead to overshoot of 10% to 40% of the step
change in setpoint step changes. To avoid this, the P-action is weakened by the
PFAC_SP parameter when a setpoint step change occurs. In typical temperature
processes, overshoot as a result of large setpoint step changes can also be
reduced by temporary use of a minimum or maximum manipulated variable
(controlled closed-loop).
Measuring the Cycle Times CYCLE and CYCLE_P
At the beginning of the tuning process, the controller sampling time CYCLE and (if
pulse control is active) the pulse generator sampling time CYCLE_P are measured.
If the measured values differ by more than 5% of the configured value, the
controller optimization will be aborted and STATUS_H = 30005 is set.
Saving the Controller Parameters (SAVE_PAR or UNDO_PAR)
When you tune the controller, the parameters are saved before tuning is started.
When tuning is completed, you can reactivate the parameter settings as they were
prior to tuning using UNDO_PAR.
PID Temperature Control
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