SIMATIC Industral Software - Tools for configuring and programming ...

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