SIMATIC Industral Software - Tools for configuring and programming ...
SIMATIC Industral Software - Tools for configuring and programming ...
SIMATIC Industral Software - Tools for configuring and programming ...
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Control configuration<br />
St<strong>and</strong>ard PID control<br />
Small <strong>and</strong> medium-sized control tasks have up to now<br />
often been implemented with compact controllers. This<br />
additional hardware requires space in the cabinet <strong>and</strong> is<br />
not very flexible. <strong>Software</strong> controllers which can be integrated<br />
into the control program are a good alternative.<br />
St<strong>and</strong>ard PID control offers a preconfigured control structure<br />
as an option <strong>for</strong> STEP 7 which can be easily adapted to<br />
different control processes. With st<strong>and</strong>ard PID control,<br />
controllers do not have to be programmed – optimal<br />
results can be achieved through parameterization.<br />
St<strong>and</strong>ard PID control comprises two components: a parameterization<br />
tool as an option <strong>for</strong> STEP 7 <strong>and</strong> function blocks <strong>for</strong><br />
the CPU. This allows the most important control tasks to be implemented.<br />
The software is there<strong>for</strong>e suitable <strong>for</strong> small to medium<br />
control tasks in all sectors.<br />
Functions<br />
The following controller types can be implemented:<br />
■ Continuous-action PID controllers<br />
■ Pulse controllers including pulse-pause signal (pulse<br />
shaper)<br />
■ Step controller<br />
Frequently used controller structures are included in the scope<br />
of supply as application examples in the <strong>for</strong>m of function<br />
blocks:<br />
■ Step controllers with line simulation<br />
■ Continuous controllers with line simulation<br />
■ Multi-loop ratio controller<br />
■ Mixture controller<br />
■ Cascade controller<br />
Parameterization<br />
The user-friendly controller structure allows functions to be<br />
switched on <strong>and</strong> off with software switches. With the parameterization<br />
interface, parameters can also be changed while<br />
the CPU is in the RUN state.<br />
16 Control configuration<br />
Controller optimization<br />
For st<strong>and</strong>ard PID control, controller optimization is included in<br />
the parameterization software.<br />
This self tuning function<br />
allows controllers to be set quickly even without exact knowledge<br />
of the plant. For this purpose, the process is activated<br />
with a step change in controller output or a setpoint change.<br />
During the settling period, the process values are automatically<br />
acquired <strong>and</strong> displayed. The program uses the values to calculate<br />
a model of the controlled system <strong>and</strong> determines the<br />
best control parameters. With self-optimization overshooting<br />
is impossible.<br />
Test functions<br />
Comprehensive test functions aid commissioning <strong>and</strong> diagnostics.<br />
Control loop displays with bar charts <strong>and</strong> plotters are<br />
available <strong>for</strong> recording the signal paths. It is possible to display<br />
the controller structure <strong>and</strong> parameters as well as their effect<br />
on the result at the same time.<br />
The clear controller structure of St<strong>and</strong>ard PID Control