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Please note that the recommended version of Scilab is 6.1.0. This page might be outdated.
See the recommended documentation of this function

# evans

Evans root locus

### Calling Sequence

`evans(H [,kmax])`

### Arguments

H

SISO linear system given by a transfer or a state space representation (see:syslin).

kmax

real (maximum gain desired for the plot )

### Description

Gives the Evans root locus for a SISO linear system in state-space or transfer form H(s) (syslin). This is the locus of the roots of `1+k*H(s)=1+k*N(s)/D(s)`, in the complex plane. For a selected sample of gains ```k <= kmax``` ,the imaginary part of the roots of `D(s)+k*N(s)` is plotted vs the real part.

To obtain the gain at a given point of the locus you can activate the datatips manager and click the desired point on the root locus.

### Examples

```H=syslin('c',352*poly(-5,'s')/poly([0,0,2000,200,25,1],'s','c'));
clf();evans(H,100);sgrid()
[Ki,s]=kpure(H) // Gains that give pure imaginary closed loop poles
plot([real(s) real(s)],[imag(s) -imag(s)],'*r')

[Kr,s]=krac2(H)```

### See Also

• syslin — définition d'un système dynamique linéaire
• sgrid — s-plane grid lines.
• zgrid — zgrid plot
• kpure — continuous SISO system limit feedback gain
• krac2 — continuous SISO system limit feedback gain
• datatips — Tool for placing and editing tips along the plotted curves.

### Comments

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