Siemens SIMATIC S7-1500T Function Manual

Using PID basic functions
7.3 TCONT_CP
PID control
Function Manual, 03/2017, A5E35300227-AC
235
7.3.3.9
Cancelling pretuning or fine tuning
To cancel pretuning or fine tuning, click on the icon, "Stop tuning".
If the PID parameters have not yet been calculated and stored, TCONT_CP starts in
automatic mode LMN = LMN0 + TUN_DLMN. If the controller was in manual mode before
the tuning, the old manual manipulated variable is output.
If the calculated PID parameters have already been saved, TCONT_CP starts in automatic
mode and works with the previously determined PID parameters.
7.3.3.10
Manual fine-tuning in control mode
The following measures can be employed to achieve an overshoot-free setpoint response:
Adapting the control zone
During tuning, "TCONT_CP" determines a control zone CON_ZONE and activated if the
process type is suitable (process type I and II) and a PID controller is used
(CONZ_ON = TRUE). In control mode, you can modify the control zone or switch it off
completely (with CONZ_ON = FALSE).
Note
Activating the control zone with higher
-order processes (process type III) does not normally
provide any benefit since the control zone is then larger
than the control range that can be
achieved with a 100% manipulated variable. There is also no advantage in activating the
control zone for PI controllers.
Before you switch on the control zone manually, make sure that the control zone is not too
narrow. I
f the control zone is set too narrow, oscillations occur in the manipulated variable
and the process value.
Continuous attenuation of the control response with PFAC_SP
The control response can be attenuated with the PFAC_SP parameter. This parameter
specifies the percentage of proportional component that is effective for setpoint step
changes.
Regardless of the process type, PFAC_SP is set to a default value of 0.8 by the tuning
function; you can later modify this value if required. To limit overshoot during setpoint step
changes (with otherwise correct controller parameters) to approximately 2%, the following
values are adequate for PFAC_SP:
Process type I
Process type II
Process type III
Typical temperature process
Intermediate range
Higher-order temperature process
PI
0.8
0.82
0.8
PID
0.6
0.75
0.96

Siemens SIMATIC S7-1500T Specifications

General

Brand	Siemens
Model	SIMATIC S7-1500T
Category	Controller
Language	English