Abstract: An unstable periodic orbit (UPO) tracking of uncertain chaotic systems is considered. Time-delayed controller with good robustness is proposed. UPO is fast and successfully tracked via the variable structure co ntrol method. The period is achieved by means of gradient descent mechanism so t hat the accurate period need not known in advance. Finally, Rossler chaos and Lo renz systems have been simulated under the controller proposed. And the results verify the effectiveness and correction of time-delayed feedback controller.

Key words: chaos, time-delayed feedback, uncertainty, variable structure control, tracking control