Disturbance rejection using SMC-based-equivalent-input-disturbance approach.

• This paper uses an SMC controller to suppress the estimation error neglected by the conventional EID approach. The application of the SMC improves the disturbance-rejection performance of the EID approach. • A variable switching gain is designed to reduce the chattering. The switching gain is dependent on the estimation error and is very small. Thus, the chattering is smaller than the conventional SMC method. • A comparison shows that the disturbance-rejection performance of our method is better than either the conventional EID approach or the conventional SMC method while the chattering is almost free. This paper uses the sliding-mode control (SMC) to compensate for an estimation error caused by the filter in an equivalent-input-disturbance (EID) compensator. The application of the SMC brings another shortcoming: The chattering problem. To solve such a problem, this paper makes use the features of the EID approach and presents a method of designing a small switching gain based on the estimation error. Combining the SMC, the EID approach, and the switching-gain design law, this paper presents a new system configuration. The presented SMC-based-EID control system not only improves the disturbance-suppression performance of the EID approach but also solves the chattering problem in the SMC. A comparison shows the validity and superiority of our method. Furthermore, the robustness of the disturbance-rejection performance with respect to measurement noise is also shown by the example. [ABSTRACT FROM AUTHOR]