How to calculate the norm of the transfer function in frequency domain?
조회 수: 11 (최근 30일)
이전 댓글 표시
To calculate the norm of the transfer function by substituting s=jω is troublesome, especially for some complicated transfer functions. Is there a way to calculate the norm directly? Thanks!
For example, transfer funciton:
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/925069/image.png)
Substituting s=jω,
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/925074/image.png)
then,
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/925079/image.png)
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/926079/image.png)
Thus we can plot the figure in frequency domain,
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/925089/image.png)
Matlab code:
omega=0:0.01:10;
G1_N=0.25e-2 .* omega .^ 2 + 0.1e1;
G1_D=((2 .* omega) - 0.15e0 .* (omega .^ 3)) .^ 2 + (0.1e1 + 0.5e-2 .* (omega .^ 4) - (omega .^ 2)) .^ 2;
G1=sqrt(G1_N ./ G1_D);
plot(omega,G1)
댓글 수: 0
채택된 답변
William Rose
2022년 3월 13일
You don't need to multiply the function by its complex conjugate to get a purely real denominator. Just divide complex numerator by the complex denominator, to get a new complex number, and take the abs() of it.
댓글 수: 3
추가 답변 (1개)
Paul
2022년 3월 13일
Check out
doc tf
to learn how to create a transfer function (tf) object. Once you have G(s) defined as a tf object use bode() to compute its magnitude (and phase if desired)
doc bode
댓글 수: 3
Paul
2022년 3월 13일
Actually, I was thinking of the Control System Toolbox. I'm not famiiar with the System ID toolbox.
If just wanting to use base Matlab, I'd probably use polyval().
참고 항목
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!