Input ports (1, 2) of 'untitled/Fuzzy Logic Controller/FIS Wizard/Def​uzzificati​on1/Merge' are involved in the loop

Hello,

while implementing a fuzzy-controller with two inputs and one output in Simulink i got the following fault message:

Input ports (1, 2) of 'untitled/Fuzzy Logic Controller/FIS Wizard/Defuzzification1/Merge' are involved in the Loop

I know that there will be many reasons for it, but what does this fault in general mean ?

Thanks a lot and best regards,

A. Reinmuth

Answer 1

[Shashank]

This may be a case of Algebraic loop formed. Basically, algebraic loops occur when an input port with direct feedthrough is driven by the output of the same block, either directly, or by a feedback path through other blocks which have direct feedthrough.

Algebraic loops are difficult to solve mathematically. Simulink does have algebraic loop solvers that will attempt to resolve this situation iteratively and give the correct answer, which in a lot of cases it does.

You can try placing unit delay blocks before the two inputs of Fuzzy Logic Controller.This will avoid the Algebraic loop.

[zhaohui luo]

Add unit delay before the input for fuzzy logic did work!