Concept of Root Locus with solved example
Root Locus Concept with solved example
The stability of any control system depends on location of roots of characteristic equation or location of closed loop poles.
If some parameters of system are varied then closed loop poles moves in s-plane. Such movement of poles in s-plane is known as Root Locus.
It was introduced by W.R Evans in 1948.
Definition:
Root Locus method is graphical representation in which movement of poles is sketched in s-plane when particular parameter of system is varied from 0 to ꚙ.
For Root Locus method gain is assumed to be parameter which is to be varied from 0 to ꚙ.
Gain K is variable parameter
If K is varied from -ꚙ to +ꚙ then each separate value of K will give separate set of location of roots of C.E ⇒ Root locus ( all locations are joined).
Types of Root Locus
Direct Root Locus
The plot when K is varied from 0 to ꚙ.
Indirect Root Locus
The plot when K is varied from -ꚙ to 0.
Q Consider a unity feedback system with G(s) = K/s. Obtain Root Locus.
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