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## Main Question or Discussion Point

Hi All,

Suppose I have the following system:

A = 1 / (S + 1) (open loop)

B = S / (2S + 1) (feedback path)

I know that the positive feedback closed loop system will thus be: A / (1 - AB), and entering this manually in matlab (as well as doing it by hand), I get:

2 s^2 + 3 s + 1

-----------------------

2 s^3 + 4 s^2 + 3 s + 1

However, when I use the following command:

sys = feedback(A,B,+1)

I get the following:

2 s + 1

---------------

2 s^2 + 2 s + 1

Is there something i'm missing?

Regards,

Suppose I have the following system:

A = 1 / (S + 1) (open loop)

B = S / (2S + 1) (feedback path)

I know that the positive feedback closed loop system will thus be: A / (1 - AB), and entering this manually in matlab (as well as doing it by hand), I get:

2 s^2 + 3 s + 1

-----------------------

2 s^3 + 4 s^2 + 3 s + 1

However, when I use the following command:

sys = feedback(A,B,+1)

I get the following:

2 s + 1

---------------

2 s^2 + 2 s + 1

Is there something i'm missing?

Regards,