MATLAB Answers

Substitute s for jw in a transfer function

조회 수: 213(최근 30일)
Inés Bodoque
Inés Bodoque 2021년 1월 11일
댓글: Inés Bodoque 2021년 1월 11일
Hi, I have a transfer function define by
G = ([1 2],[3 4 5]) (as an example)
I want to change the 's' for 'jw'. Does anyone know how to do it?
I've tried subs(G,{s},{1j*omega}) but it didn't work.

채택된 답변

Jon
Jon 2021년 1월 11일
Hi,
I think you mean that you define your transfer function using (you forgot the tf() in your example)
G = tf([1 2],[3 4 5]) %(as an example))
Then if you want to evaluate it at a particular frequency, that is a specific value of jw, you can use
w = 3; % for example 3 radians/sec
val = evalfr(G,j*w)
You can also use the freqresp function to evaluate it for multiple values along the jw axis
  댓글 수: 2
Inés Bodoque
Inés Bodoque 2021년 1월 11일
It worked! Thank you very much

댓글을 달려면 로그인하십시오.

추가 답변(1개)

Pat Gipper
Pat Gipper 2021년 1월 11일
Matlab uses the reserved constant "i" which is set equal to sqrt(-1). Using your transfer function as defined try the following which will result in the variable "G" which will be a complex number.
num=1*i*w+2;den=3*(i*w)^2+4*i*w+5;G=num/den;
  댓글 수: 2
Inés Bodoque
Inés Bodoque 2021년 1월 11일
Thank you for your answer! I need this for a project from one of my subjects and I am not allowed to use the Control Systems Toolbox, that's why I have to do it this way

댓글을 달려면 로그인하십시오.

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by