Generalized Finite-Time Variable Gain Composite ADRC for Nonlinear Systems and Its Application to Vehicle Active Suspensions

In this article, a generalized finite-time variable gain composite active disturbance rejection control (FTVGCADRC) method is proposed for${\boldsymbol{n}}$th order nonlinear systems. The proposed FTVGCADRC method includes the generalized finite-time variable gain composite tracking differentiator (FTVGCTD), the generalized finite-time variable gain composite extended state observer (FTVGCESO), and the generalized finite-time variable gain composite controller (FTVGCC). The designed generalized FTVGCADRC achieves smooth switching between the linear ADRC and finite-time ADRC, thereby combining the advantages of both linear ADRC and finite-time ADRC. By employing error-driven variable gain mechanisms, both the nonsmooth switching problem and the switching stability problem are avoided from analysis. Moreover, the stability analysis of the generalized FTVGCADRC is performed by robust analysis methods, and the existence of feasible solutions is discussed and expressed explicitly. Finally, the generalized FTVGCADRC method is applied to vehicle active suspensions, and experimental results are presented to demonstrate its effectiveness.