Monday, September 3, 2012

3-Point Stepper Control with SIMATIC S7-1200
Problem 
The valve of a mixer tap shall be controlled according to a desired given temperature.
A three-way mixing valve with valve actuator is used. The valve is digital controlled in both directions. This is referred to as a 3-point stepper control.
Varying the valve position can yield any mixing ratio of hot and cold entering water and so the water outlet temperature.

Solution
For SIMATIC S7-1200 as of firmware V2.0, the development environment STEP 7 V11 provides the "PID_3Step" 3-point stepper control block.


The application on hand provides quick configuration and commissioning of your mixer tap.
The application also contains a simulation of the controlled system, which enables familiarizing yourself with all functions of "PID_3Step".
The
following
features can be conveniently operated via KTP1000 Basic PN:
  • Switching between automatic and manual mode
  • Transition time measurement of the valve
  • Visualization of the valve position
  • Trend curves of setpoint, process value and output value
  • Switching between the real controlled system and the simulation
  • Disturbance value control in simulation mode
  • Specifying the behavior in the case of errors and their simulation
  • Specifying the deadband width for energy saving operation
  • Manually specified control parameter and automatic tuning
  • Online monitoring of the "PID_3Step" controller block
  • Modifying the configuration during runtime


For more information,please visit SIEMENS website








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