Discrete-time sliding mode control systems

Abstract

The main philosophy of discrete-time variable structurecontrol systems is the same as its continuous-time versionwhich is the establishment of a sliding regime of the statetrajectories on a certain hypersurface.In this thesis, sliding mode cohtrol systems which usesa discrete-time switching control mechanism together withdiscrete-time feedback signals will be considered. Theconditions which ensure the existence of a quasi-slidingmotion in such systems are presented. The output feedbackproblem in discrete-time variable structure control systemsis investigated in order to avoid the necessity of the fullstate vector which is an important drawback of the currentvariable structure theory.One of the major problems in discrete-time variablestructure control systems is the high frequency chatter dueto the non-ideal sliding motion. The problem becomes moreimportant with the use of output feedback. The derivation ofspecial control laws which uses full output feedback withoutintroducing any chatter to the system is presented. To newadaptive control algorithms utilizing output feedback arederived. One of the algorithms is corrective-adaptivealgorithm the ather is a predictive-adaptive algorithm.