Rlocusplot() does not plot the roots

Hello guys. I’m having trouble plotting the root locus diagram. He doesn’t show my roots.

X(s) = \frac{6s+204}{s^3+10s^2+34s}

using ControlSystems
sys2 = tf(
[6,204],
[1,10,34,0]
)
rlocusplot(sys2)


The Julia code above draws the following graph:

But the scilab equivalent shows a root close to -35.

How do I show the hidden root?

Try setting the xlim keyword argument.

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As @baggepinnen says, try

rlocusplot(sys2, xlims=(-40, 10))


Part of the rlocusplot recipe (in src/root_locus.jl) is the line,

xlims --> (max(-50,minimum(redata) - 1), clamp(maximum(redata) + 1, 1, 50))


This finds the limits of the calculated root positions as the gain K is swept from 1e-6 to 500, but unfortunately this doesn’t include the location of the zero in this case.

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Another package to analyse control systems is controlz.jl:

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