Unknown inputs' adaptive observer for a class of chaotic systems with uncertainties

This paper treats the adaptive synchronization problem of a class of uncertain chaotic systems with uncertainties and unknown inputs in the drive-response framework. A robust adaptive sliding mode observer-based response system is designed to synchronize a given chaotic system without the knowledge of upper bounds of uncertainties and unknown inputs. Further, the unknown inputs can be approximately recovered directly by the concept of equivalent control signal. To highlight our method, we improve the robustness of ciphering in a secure communication system. Computer simulation is also given for the purpose of illustration and verification.