How to define the output of Fuzzy Controller as a change in the duty cycle for DC DC converter

Hi. I'm trying to control a DC DC converter with a Fuzzy controller. The output "u" of the Fuzzy controller will control the duty cycle "d" of the MOSFET, but I want the output to be the change in the duty cycle that will stabilize the output voltage. Summing up, I need an output such that d(k) = d(k-1) + u(k). However, when I simulate, the output is a constant value that only depends on the inputs, and not the change in the duty cycle that I need. I'm pretty sure that my fuzzy controller is right, because I'm using one that I found in a paper. How should I proceed?

[Ahmed Ibrahim]

same problem here

[Sam Chak]

@Ahmed Ibrahim, I'm not familiar with the diagram.

Can you explain using a simple system such as a double integrator, ?

Answer 1

[Sam Chak]

Since the Simulink model is not provided to investigate why the fuzzy controller continues to produce a constant output value when a change in the duty cycle is desired, and if you are confident that the fuzzy controller was correctly designed according to the fuzzy rules published in a journal article (presumably authored by a true expert in fuzzy logic and DC-to-DC converters), then the only explanation for the issue is that your 'copied' fuzzy controller is not properly scaled to your version of the DC-to-DC converter.

When the input value lies outside the range of the fuzzy input variable, none of the rules will be triggered, and the internal algorithm will automatically set the defuzzified output value to its mean range value. Despite the fuzzy rules being correct, the antecedent part of the fuzzy controller may not be appropriately scaled to the operating range of your DC-to-DC converter.

Extending the range of the fuzzy input variable and adjusting the parameters of the affected membership functions should resolve the issue.