Rootlocus HELP Matlab rlocus() function

[dammadmin]

Rootlocus HELP

I need to find the rootlocus for a unity feedback system with G(s) = K / P(s)

the gain is not fixed value but is variable K. I can find the rootlocus on matlab when K= a value but for general K.. how can i find the root locus??? ANy idea..

 

[JoannesPaulus]

Rootlocus HELP

help rlocus
RLOCUS Evans root locus.

RLOCUS(SYS) computes and plots the root locus of the single-input,
single-output LTI model SYS. The root locus plot is used to
analyze the negative feedback loop

+-----+
---->O----->| SYS |----+---->
-| +-----+ |
| |
| +---+ |
+-------| K |<----+
+---+

and shows the trajectories of the closed-loop poles when the feedback
gain K varies from 0 to Inf. RLOCUS automatically generates a set of
positive gain values that produce a smooth plot.

RLOCUS(SYS,K) uses a user-specified vector K of gain values.

RLOCUS(SYS1,SYS2,...) draws the root loci of multiple LTI models
SYS1, SYS2,... on a single plot. You can specify a color, line style,
and marker for each model, as in
rlocus(sys1,'r',sys2,'y:',sys3,'gx').

[R,K] = RLOCUS(SYS) or R = RLOCUS(SYS,K) returns the matrix R of
complex root locations for the gains K. R has LENGTH(K) columns
and its j-th column lists the closed-loop roots for the gain K(j).