Discrepancy when plotting step response of two identical transfer functions.

9 次查看（过去 30 天）
Benjamin
Benjamin 2025-9-13
评论： Star Strider 2025-9-13
I generated an idtf model from time domain data using the System Identification Toolbox (SIT). The model is "tf2" seen below.
When I plot the step function of the model inside of MATLAB everything seems fine, the response matches what is seen in the SIT:
But if I use the coefficients from tf2 and create a transfer function using tf(num,den,Ts), then I get an entirely different response.
(No, it isn't the z^-1s, keep reading!)
Somehow, if I grab the numerator and denominator from tf2 then it works. Even though it is the EXACT same transfet function as " hz" plotted above.
As my last check I tried building an idtf model using the coefficients. But it doesn't even match the original tf2 step response, even though they are the EXACT SAME THING.
This makes no sense and I'd appreciate any help I can get on the matter.

请先登录，再回答此问题。

采纳的回答

Star Strider
Star Strider 2025-9-13
We do not have the original data.
I suspect that you are seeing the loss of precision due to using only 4 significant digits of a 15-significant digit result.
.
  2 个评论
Benjamin
Benjamin 2025-9-13
That was correct, each display of the transfer function only had 4 significant digits when the underlying numbers being processed were much longer. Thank you!

请先登录，再进行评论。

更多回答（0 个）

类别

在 Help Center 和 File Exchange 中查找有关 Transfer Function Models 的更多信息

标签

产品


版本

R2024b

Community Treasure Hunt

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

Start Hunting!

Translated by