# How do I find the fourth order transfer function from this step response diagram?

I have the following diagram of a system's step response:

I'm having trouble understanding how to calculate the system's transfer function for fourth order. hir: How do I find the second order transfer function from this step response diagram? I have learned how to do it for the second but I do not know how to calculate this for the fourth order.

• Manually do it using a simulator to mimic the response. A bit fiddly of course but, that's what you get with 4th order filters. Aug 4 '20 at 16:51
• Thanks. I did it with matlab and i got it. i want to know is there any method to calculate it like 2. order? Aug 4 '20 at 16:56
• You can probably find $\omega_n$ from the oscillations on that output, but being able to determine $p_1,p_2,\xi$ will not be as easy. If you have that data, I would suggest using some ARMA toolbox to identify such 4th order model.
– jDAQ
Aug 4 '20 at 16:56
• Do you have Matlab's system identification toolbox?
– Chu
Aug 4 '20 at 19:41
• I can make an active filter look like that on an interactive simulator, but why bother? Aug 5 '20 at 1:59