What migh be producing these huge amount of Warnings in my FL control?

Question

Tony Castillo 2022-2-18

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https://ww2.mathworks.cn/matlabcentral/answers/1652980-what-migh-be-producing-these-huge-amount-of-warnings-in-my-fl-control

回答： Sam Chak 2022-2-23

Dear all,

I have a battery control using Fuzzy Logic, it seems to be working properly, but I am receiving a tons of warnings like these:

        > In fuzzy.internal.utility.throwWarning (line 14)
        In PVGeo_based_LG (line 123) 
        Warning: In 'Full_PED_FL/FL_Battery_Control/Fuzzy Logic
        Controller', no rules fired for Output 2. Defuzzified output value set to its mean range value 0.5. 
        > In fuzzy.internal.utility.throwWarning (line 14)
        In PVGeo_based_LG (line 123) 
        Warning: In 'Full_PED_FL/FL_Battery_Control/Fuzzy Logic
        Controller', no rules fired for Output 1. Defuzzified output value set to its mean range value 0.5. 

What does this mean ? how can I overcome this misbehaviour?

Best regards

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Sam Chak 2022-2-22

Hi @Tony Castillo

I see. When your Power Error = 0, none of rules is fired, because Power Error only has Negative MF (< 0) and Positive MF (> 0).

It is similar to the common issue in low-level collision avoidance systems. If the Obstacle is on the left, then STEER right (+ve angle). If the Obstacle is on the right, then STEER left (–ve angle). When the Obstacle is exactly in the middle, it creates a "confusion" because no rules fired for the STEER output. And if the defuzzified output value set to its mean range value, which is 0° (no steering occurs), then disastrous collision may happen.

The same like playing in Badminton Doubles. If opponents are in a defensive position, and the center of their court is open, then smashing to the middle will cause confusion becaise the opponents have to mentally decide in a split second who must return.

As a first-line rectification, try modifying the membership functions in Power Error to look like in the figure below where the adjacent triangular fuzzy sets cross at 0.5, in which the middle truth-value 0.5 can be interpreted as "undecided". If you fix that, then Rules #5 , #8, #11, and #14 will be fired.