How to get transfer function from circuit in simulink without exact values

Hello,

i would like to ask if there is any way to obtain transfer function just by drawing circuit in simulink? I want TF expressed like this:

(video from matlab team) -> https://youtu.be/EXzTgGPdfzs?feature=shared&t=261

So i can make script for plotting root locus for various loads at the output.

thanks

Answer 1

[Pratyush]

Hi ahmed,

To obtain a transfer function from a Simulink model, follow these summarized steps:

1. Design your system in Simulink accurately using the appropriate blocks.
2. Linearize your system using MATLAB functions such as linearize('YourSimulinkModel') to get a linear model approximation.
3. Convert the linear model to a transfer function using MATLAB's tf function, like [num,den] = tfdata(sys,'v'), where sys is your linearized system.
4. Create a script to plot the root locus for various parameters using the obtained transfer function coefficients (num and den) with commands like sys_tf = tf(num,den); rlocus(sys_tf).

Hope this helps.

[ahmed]

Thanks!

Just for clarification can this plot also variable load?

If i have resistive load connected at the output of LC filter like this

https://www.researchgate.net/publication/343888988/figure/fig7/AS:928795506786307@1598453513796/Figure228-Multiple-LC-filter.jpg

And i draw this circuit in simulink and use linearize command i think i will get TF in polynomial form where i can not see variable "RL" for resistive load.

Ive seen it here

https://nl.mathworks.com/matlabcentral/answers/131093-transfer-function-of-a-simple-circuit-using-simulink

after i close feedback, i would like to plot rlocus for RL in range 10ohm to 10kohm.

I am newbie so really sorry for misunderstood =)