Feedback loop using MATLAB function block in Simulink gives wrong answers

Hi, I am just implementing a very basic simulink function block to use a feed back loop as a test for its application in a larger project. According to the code the result should be 10 always. However I am getting -10 most of the time with some vague results initially of order 10^(-16). This is my function block code

 function y = fcn(u,v)
%#codegen
y = 2*v+u;
disp(y);

This is the simulink diagram

What could be off here?

Answer 1

[Abel Babu]

Hi Amol,

The issue that you are facing might be due to the formation of algebraic loops, i.e a direct feed through, more about the same can be read here: https://in.mathworks.com/help/simulink/ug/algebraic-loops.html

Hence, a way out of this would be to introduce a delay. If you are using continuous time, use the Transport Delay else use the Delay (Simulink/discrete)

Abel