  Based on the principle of chaotification for continuous-time autonomous
systems, which relies on two basic properties of chaos, i.e., globally bounded
with necessary positive-zero-negative Lyapunov exponents, this paper derives a
feasible and unified chaotification method of designing a general chaotic
continuous-time autonomous nonlinear system. For a system consisting of a
linear and a nonlinear subsystem, chaotification is achieved using separation
of state variables, which decomposes the system into two open-loop subsystems
interacting through mutual feedback resulting in an overall closed-loop
nonlinear feedback system. Under the condition that the nonlinear feedback
control output is uniformly bounded where the nonlinear function is of
bounded-input/bounded-output, it is proved that the resulting system is chaotic
in the sense of being globally bounded with a required placement of Lyapunov
exponents. Several numerical examples are given to verify the effectiveness of
the theoretical design. Since linear systems are special cases of nonlinear
systems, the new method is also applicable to linear systems in general.
