Adaptive variable structure control system with free chattering

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. The adaptive VSC method is presented to adjust the magnitude of the signum term. An application of both methods is illustrated by investigating an electrohydraulic position control system in the presence of parametric uncertainties and external disturbances. The result of the investigation, including computer simulation, demonstrate that chattering at the VSC output and chattering of state variables are both suppressed and that the system is well-controlled in the presence of uncertainties and disturbances