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

enter image description here

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.

enter image description here

  • 1
    \$\begingroup\$ 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. \$\endgroup\$
    – Andy aka
    Aug 4 '20 at 16:51
  • \$\begingroup\$ Thanks. I did it with matlab and i got it. i want to know is there any method to calculate it like 2. order? \$\endgroup\$
    – dinoo
    Aug 4 '20 at 16:56
  • \$\begingroup\$ 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. \$\endgroup\$
    – jDAQ
    Aug 4 '20 at 16:56
  • 1
    \$\begingroup\$ Do you have Matlab's system identification toolbox? \$\endgroup\$
    – Chu
    Aug 4 '20 at 19:41
  • \$\begingroup\$ I can make an active filter look like that on an interactive simulator, but why bother? \$\endgroup\$ Aug 5 '20 at 1:59

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