Sliding mode control: Concepts ideas and impressions

Variable structure control systems are known to be computationally efficient and robust with respect to matched uncertainty and external disturbance. Therefore, they have indisputably become an exciting research topic and also a significant application area. Moreover, recently sliding modes have become increasingly important for observer design, fault detection and fault tolerant control. Motivated by the growing interest in these topics, in this paper we acquaint the reader with basic notions, discuss selected concepts and present some milestone developments which appeared in this field over the last half a century. In particular we briefly present some issues in discrete time sliding mode control, shed light on continuous time terminal sliding mode control, demonstrate the reaching law based approach, comment on variable structure control without the reaching phase, and consider selected sliding surface design methods.