Estimating regions of asymptotic stability using non-sign-definite Lyapunov functions

A Lyapunov function, for which both V and V¿ are sign-definite in only certain regions of the phase plane, is used to estimate the region of asymptotic stability of the equilibrium point of a nonlinear control system. An analytical result is obtained by restricting attention to a subregion where V and V¿ are signdefinite.