Computer-Controlled Variable Structure Systems: The State-of-the-Art

Variable Structure Systems (VSSs) have been studied extensively for over 60 years and widely used in practical applications. A particular interest in VSS is the so-called Sliding-Mode Control (SMC), which is simple in control design and robust in parameter variations and disturbances. Modern control systems nowadays are implemented through computers. This presents challenges for SMC based VSS because the digital nature of computer-control weakens the essential assumption of SMC, that is, the switching frequency should be unlimited in order to deliver effective disruptive control actions. Extensive research activities have been since undertaken in computer-controlled VSS over the last thirty years. This survey provides a comprehensive account of the key developments in this field and examines the key technical research challenges for the future developments.