How to generate frequency-response data?

[ErikQQY]

Hello guys! Many thanks for your awesome works! In MATLAB, there is frd to create frequency-response data model. But how to do the same thing in ControlSystems.jl?

[baggepinnen]

Hey and thanks :)
There is no FRD object in ControlSystems.jl, see ControlSystemIdentification.FRD

[ErikQQY]

Wow! Thanks a lot! That solve my problem! BTW, I think it would be nice to have bodeplot method for FRD to generate bodeplot, is there any plan for this? @baggepinnen

[baggepinnen]

Just call plot on the frd::FRD

[ErikQQY]

Thank you for your quick response! There are complex numbers in my FRD, so if I directly call plot it would throw errors🥲

[baggepinnen]

Have you tried? I'm asking because I know it works ;)

using ControlSystemIdentification, ControlSystems
w = exp10.(LinRange(-2, 2, 200))
r = freqresp(ssrand(1,1,3), w).parent
frd = FRD(w, r)
plot(frd)

[ErikQQY]

Oops, the old version of ControlSystemIdentification.jl caused the problem.🤣 Anyway, thanks a lot!!

[ErikQQY]

@baggepinnen Hi there! The plot method of FRD only generate the Magnitude-Frequency plot, so I think it would be great to create both Magnitude-Frequency and Phase-Frequency plot like bodeplot we already have in ControlSystems.jl for FRD type :)

[ErikQQY]

Besides, I think add nyquistplot, margin and nicholsplot method for FRD type would also be great ;)