Phase shift of transfer function

15 次查看（过去 30 天）
Matija Milenovic
Matija Milenovic 2020-9-1
回答： Swetha Polemoni 2020-9-4
I'm trying to compute the phase shift of a transfer function (accelerance), but I'm having issues.
The transfer function was computed by dividing the magnitude of the system output by the input (please see here).
I've been using `pwelch()` to compute all of the functions in the frequency domain, but from the best of my understanding, the Welch PSD estimate outputs a real-valued vector, so there's no way to get a phase shift.
When I try to use the `fft()` function, the result (magnitude) doesn't look right, so I'm not sure if I would trust the phase shift. Below is the code I used to compute the transfer function:
% Welch Acceleration
[pa,f] = pwelch(ay,1000,10,0:10:10000,Fs);
% Welch Force
[pf,f] = pwelch(fy,1000,10,0:10:10000,Fs);
% Transfer function
H = pa./pf;
If someone could point me in the right direction it would be appreciated.

请先登录，再回答此问题。

回答（1 个）

Swetha Polemoni
Swetha Polemoni 2020-9-4
Hi,
As per my understanding, you want to calculate transfer function a system from its input and output. In general transfer function can be calculated by dividing output of the system in frequency domain by input/excitation given to system in frequency domain. Refer this for better understanding.
-> If only magnitude of input and output in frequency domain is used for calculating transfer function, all the system’s information cannot be understood. So if there is a phase shift between output and input , that is because of the system.
-> "pwelch()" is a power spectral density estimate. As the name suggests, it is always real since power is real . So, by dividing PSD of output with PSD of input may only give the magnitude information of the system.
Transfer function can also be estimated using "tfestimate()".

类别

在 Help Center 和 File Exchange 中查找有关 Parametric Spectral Estimation 的更多信息

标签

产品


版本

R2020a

Community Treasure Hunt

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

Start Hunting!

Translated by