On The Lyapunov Theory: Application To LTI Systems

This brief paper  is  a review of   the classical  Lyapunov theory, also referred to as  Lyapunov’s direct method  or Lyapunov’s second method. The Lyapunov theory  uses the concept of Lyapunov function of the system to draw conclusions on system  stability, without actually solving the differential equation of the system motion. Some primary definitions are recalled and uniqueness solution issue for the Lyapunov equation is addressed for  linear systems.

Key words:  Asymptotic Stability, Lyapunov Stability, Lyapunov  function, Linear Time Invariant System (LTI).