Application of Smith prediction technique in designing of variable structure control systems for plants with time delay

High frequency chattering is undesirable in many cases. The reluctance of using variable structure control (VSC) is mainly due to the concern of excess chatter. This paper presents two methods for solving the existing control chattering problem. The plant augmentation method introduces the strategy for solving the existing problem by augmenting the plant with a pure integrator. Being able to apply Smith prediction technique in the VSC design of plants with time delay is due to this strategy. The adaptive VSC method is presented to adjust the magnitude of the signum term according to the estimated system parametric uncertainties and external disturbances via a Luenberger observer. An application of both methods is illustrated by investigating a second order system in the presence of parametric uncertainties and external disturbances. The simulation results show that both methods are effective in making Smith prediction technique applicable to VSS, are effective in reducing control chattering, and providing robustness and stability for the applied system