  Adaptive controllers are designed to synchronize two different chaotic
systems with uncertainties, including unknown parameters, internal and external
perturbations. Lyapunov stability theory is applied to prove that under some
conditions the drive-response systems can achieve synchronization with uniform
ultimate bound even though the bounds of uncertainties are not known exactly in
advance. The designed controllers contain only feedback terms and partial
nonlinear terms of the systems, and they are easy to implement in practice. The
Lorenz system and Chen system are chosen as the illustrative example to verify
the validity of the proposed method. Simulation results also show that the
present control has good robustness against different kinds of disturbances.
