Controller Design problem with variable trasnfer function.

[devilwiss]

Suppose we have a linear system with the following relation :

S(t)=E(t)+1;

S(t): is the output of the system

E(t) : is the input of the system

if we want to extract the transfer function from the previous relation, we would get :

S/E=1+1/(s*E) with s is the laplace variable.

as you see, the transfer funtion depend on the input !!!

All i know is that for the design of a regulator we must have a known transfer function (plant) which is independent of the input

if we suppose we want to put this system in a closed loop, how can we design a controller with a variable transfer function ???

 

[albert22]

Please somebody correct me if I am wrong>
I think that the system is not linear. Because with E(t)=0 the output is non zero. And a*S(t) not equal to a*E(t)+1.
And Laplace works for LTI systems.

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It is trivial to implement in the time domain.
Adding an offset of one with an operational amplifier .
Or in the digital domain as s=e+1 where s is the sampled s(t).

 

[devilwiss]

Thanks you're totally right