→Feedback loop
also known as feedback path, according to →IEC-standard: A feedback path is said to exist in a →network when the output of a →function or →function block is used as the input to a function or function block which precedes it in the network; the associated →variable is called a feedback variable. ... A feedback variable can also be an output element of a function block data structure.
Examples for feedback loops in the FBD-editor |
|
---|---|
|
This shows an explicit feedback loop. The variable An explicit feedback loop is caused by a line connecting an output to a preceding input. Here the output of the →value field with the variable |
|
This shows an implicit feedback loop. Here the variable An implicit feedback loop is caused by using a variable receiving its value from an output and being the input value to a preceding input. Here the variable |
Feedback loops must be resolved for the →evaluation of networks.
Certain types of feedback loops are supported in Neuron Power Engineer (), others are not ().
, if the output of a function block is connected to a previous input |
, if the output of a function is connected to a previous input and there is a variable in between (this variable might even be the output variable of a function block in between) |
, if the output of a function is connected to a previous input and there is no variable in between By default, feedback loops for functions without a variable in between are highlighted as errors. No execution order is shown for these network elements and it is not possible to build and load the application onto the PLC. |