Matlab's feedback function is used to obtain the closed loop transfer function of a system. Example:
sys = feedback(sys1,sys2) returns a model object sys for the negative feedback interconnection of model objects
sys2. To compute the closed-loop system with positive feedback, use sign = +1, for negative feedback we use -1.
My question arises when we have a system of the following type:
According to these docs, we can use feedback to create the negative feedback loop with G and C.
sys = feedback(G*C,-1)
This is a source of confusion, shouldn't the above be:
sys = feedback(G*C,1,-1)? These are not the same.
However, looking at these docs, for a unit loop gain k, you can compute the closed-loop transfer function T using:
G = tf([.5 1.3],[1 1.2 1.6 0]); T = feedback(G,1);
Why are we using
1 and not
-1? This is still negative feedback and not positive feedback.