Performance Enhancement for an Equivalent-Input-Disturbance-Based Control System Using a Sliding-Mode Controller

This article presents a sliding-mode-control-based-equivalent-input-disturbance (SMCEID) approach that enhances the disturbance-rejection performance of a plant. The control scheme includes a conventional equivalent-input-disturbance (EID) estimator and a newly added sliding-mode controller (SMC). While the EID estimator estimates and compensates for disturbances, there is a disturbance-rejection error caused by the filter in the EID estimator. This error is determined by the state-observation error. The SMC set the state-observation error as a sliding-mode surface. A binary-search algorithm is devised to select the gain of the SMC. The selected gain ensures the sliding-mode surface converges to the origin, thus eliminating the error and enhancing the disturbance-rejection performance. Employing the SMCEID approach for a Stewart-platform control system demonstrates its validity.