How to define transfer function as function in s

In control systems, we use transfer functions a lot. One way to define transfer function is merely to use tf(). For example, we could define such transfer function as

s=tf('s');
G=(s+1)/(s+3);

But what I would like to do is to define G as G(s) without explicitly defining the underlying transfer function and treat it as transfer function so that I can use Control Toolbox (i.e. feedback(), series(), parallel(),...,etc) to carry out some manipulations. How one can achieve this ?

[Bandar]

come on! not even a hint from staff?

[Star Strider]

You might be able to do something like that in the Symbolic Math Toolbox (an experiment I have not done), however the Control System Toolbox does not do such symbolic representations.

You would then need to take the Symbolic Math Toolbox results manually to the Control System Toolbox, and code them appropriately.

[Bandar]

I've tried to use Symbolic Math Toolbox but Control systems toolbox yields errors since these expressions are not defined as transfer functions.

[Star Strider]

I realise that. The point is that you can do the symbolic manipulations in the Symbolic Math Toolbox and then manually express the results as Control System Toolbox objects.

[Bandar]

I have to use some Control systems toolbox functions.

Answer 1

[Rohit Pappu]

Functions like feedback() , series() etc, take in dynamic system models as input arguments. Additional information about dynamic system models can be found here