From time to time there will be a thread on the construction of a root locus. These were methods used long before computers achieved wide availability. They are especially useful for transfer functions of third and higher orders.
For a system with a loop transfer function G(s)H(s), the first five rules are:
This is not an exhaustive list, but should suffice to get started.
For a system with a loop transfer function G(s)H(s), the first five rules are:
- The number of branches of the root locus equals the number of closed loop poles.
- The root locus is symmetrical about the real axis.
- On the real axis for K > 0 the root locus exists to the left of an odd number of real-axis, finite open-loop poles and/or finite open-loop zeros
- The root locus begins at the finite and infinite poles of G(s)H(s) and ends at the finite and infinite zeros of G(s)H(s).
- The root locus approaches straight lines as asymptotes as the locus approaches infinity. Further the equation of the asymptotes is given by the real axis intercept, σa and angle, θa