How would I model this transfer function in simulink

Hi does anyone know how I would model this transfer function in simulink. Which block would I need to use. Thanks.

[MRR]

Hi,

Did you take a look to the Matlab documentation? Take a look here:

https://es.mathworks.com/help/control/examples/specifying-time-delays.html

-M

Answer 1

[Ameer Hamza]

If you have Control system toolbox, then you can use LTI system block: https://www.mathworks.com/help/control/ref/ltisystem.html to implement a transfer function with input delay in Simulink. Check the attached Simulink file (saved in R2020a) for example.

[Uzair Akhtar]

Thanks. Im not sure what I need to input in this LTI system block.

[Ameer Hamza]

You need to use the input signal U(t), e.g., step signal, impulse signal, etc. as input to this block. The input signal can be anything, and you need to decide which signal it is. You must have an idea what signal you will input to the system.

[Uzair Akhtar]

Sorry Im a bit new to this. We were meant to find the PI and PID controller settings and develop a model in simulink to confirm the controller design gives an effective closed loop system to a step input. I made this model in simulink to confirm the PI controller. Im just unsure how to model the transfer function I mentioned in my previous comment instead of the one I have in this model (1/s^3+2s^2...).

[Ameer Hamza]

Just replace the transfer function block in your model with LTI system block in my model. And the open the LTI system block and change the LTI system variable field to

tf(1,[1 2 4 1], 'InputDelay', 0.25)

This adds a delay of 0.25 to your transfer function.

[Uzair Akhtar]

Sorry, the transfer function in the model in my previous comment is incorrect, that was just used for a different question. Its this tf I need in the system block.

[Uzair Akhtar]

The equation expanded is 10exp(-0.25s)/(4.2s^2+4.7s+1)

so would that be tf(10,[4.2 4.7 1], 'InputDelay, 0.25)

[Ameer Hamza]

Yes, that is correct.

[Uzair Akhtar]

Ah ok thank you for the help