Creating transfer function (using tf) with unknowns in it

How to create a transfer function with unknown constant in it.

I have function of ' sys_tf = (B) / (s + A) '

i am using 'syms' command to declare the unknowns. my code is as below.

syms a b

sys_tf = tf([b],[1 a]);

is it possible? what's wrong in this?

please help

Answer 1

[Stephan]

You might want to work with tuneable models / tuneable parameters.