How to plot transfer function with cos or sin

When I want to print a transfer function such as (p*(cos(w1*z)-1))/(z.*z-2*cos(w1*z)+1), I found that most case include the official guidance of matlab use command ‘tf“.But it seems that tf can only be used to create functions that only contains some simple stuff like s^2+9s+1. Here's question: what shoulf I do to create functions with cos or sin or whaterever else so that i can easily put i into other functions like 'bode'?

Answer 1

[Abderrahim. B]

Hi You have those cosine components which means that your system is non linear,and transfer function is only for linear systems. What I suggest is to linearize your model, to do so there is a function called linearize(). Another option is to do system identification if you have some measurements (Input/output)..

Hope this helps