A Discrete-Time Equivalent-Input-Disturbance Approach Based on Joint Minimum-Variance Unbiased Disturbance and State Estimation

This article develops a discrete-time equivalent-input-disturbance (EID) approach that rejects disturbances for a plant. A control system based on the approach includes a simultaneous EID and state estimation algorithm, which is newly presented by applying the minimum-variance unbiased estimation technique. Compared with a conventional EID estimator, the presented algorithm does not need to design a filter, which avoids the degradation of the performance of a control system due to improper selection of the filter parameters. Three theorems are presented to guarantee the stability of the presented algorithm. In addition, a method of designing a control law employing the state and EID estimates is explained. Speed control experiments for a two-mass experimental system demonstrate the validity of the approach.