Siemens Welding System ST PCS 7 Manual De Usuario

ES software

Siemens ST PCS 7 · November 2007

4

Examples of editable OS standard displays (faceplates) from the PCS 7 

library

Preconfigured and tested blocks, faceplates and symbols are 

organized in I&C libraries and form the basic elements for the 

graphic configuration of automation solutions. The use of these 

library elements plays a major role in minimizing the engineering 

input and project costs.
The comprehensive range of blocks can be categorized as fol-

lows:
• Simple logic and driver blocks 
• Technological blocks with integral operation and signaling 

functions such as PID controllers, motors or valves

• Blocks for integration of PROFIBUS field devices in accor-

dance with PROFIBUS PA profile 3.0 (including standardized 

evaluation of the process value status)

• Blocks with more advanced control algorithms for Advanced 

Process Control (APC) functions

Advanced Process Control (APC) functions
The APC functions concentrated in separate blocks expand the 

PID-based control functions of SIMATIC PCS 7 by more ad-

vanced control algorithms, e.g.:
• Model-based multi-variable controller
The use of a multi-variable controller is recommendable for com-

plex processes where several variables which are mutually de-

pendent have to be controlled. Separate control of the individual 

variables, e.g. using PID controllers, has the disadvantages that 

interactions result in different effects on the respective variables. 
The model-based ModPreCon multi-variable controller inte-

grated in SIMATIC PCS 7 separately analyzes the response of up 

to four mutually dependent variables over a longer period of 

time. A parameter matrix is calculated from the results, and used 

by the ModPreCon for optimum control of the variables. 

:

The ModPreCon makes great demands on memory and processing time 

of the designated automation system. For that reason, please check the 

resources of the designated automation system before use. We recom-

mend the use of an automation system of type AS 416 or higher. 

• Setting of control parameters dependent on working point
The GainSched block has been designed for variable setting of 

controller parameters depending on the working point in non-lin-

ear controlled systems. The block functions similar to the poly-

gon block, and can derive three separate output variables from 

the response of an input variable, and apply these as control pa-

rameters for a linked controller block. The GainSched block then 

adjusts the control parameters of the combined controller de-

pending on the response of the actual value. 
The faceplate of the GainSched block can be called from the 

faceplate of the associated controller.
• Monitoring of control quality
The ConPerMon block can be used to monitor the quality of a 

controller block according to a patented procedure. The set-

point, actual value and manipulated variable of the controller 

block (e.g. PID controller) are connected to the ConPerMon 

block which determines the control quality using these online 

values. The block can trigger a warning or alarm depending on 

the deviation from a reference value, e.g. the control quality de-

termined during commissioning.
The faceplate of the ConPerMon block can be called from the 

faceplate of the associated controller. OS displays can be gen-

erated during engineering which list all deviations in the control 

quality of a plant or unit. The plant operator can use these dis-

plays to recognize problems early, and to analyze and specifi-

cally eliminate such before they result in serious deficiencies or 

a production failure.

The PID Tuner is a function integrated in the CFC for optimization 

of the CTRL_PID and CTRL_S software controllers. The optimum 

parameters for a control loop can then be determined for PID, PI 

and P control modes in defined steps. 
The tool is suitable for optimizing controlled systems with or with-

out an integral component. Optimization can be carried out in 

manual or automatic mode. The transient response of the con-

trollers with the determined parameters can be checked by de-

fining jumps. The controller parameters can be saved, and re-

called as required.
During determination of the controller parameters, the typical 

controller values (actual value, setpoint, manipulated variable) 

are recorded by a trend function.

© Siemens AG 2007