Robust control of nonlinear MAGLEV suspension system with mismatched uncertainties via DOBC approach

Robust control problem of a class of uncertain systems that have disturbances and uncertainties not satisfying “matching” condition, is investigated in this paper via a disturbance observer based control (DOBC) approach. In the context of this paper, “matched” disturbances/uncertainties refers to the disturbances/uncertainties enter the system through the same channels as the control inputs. By properly designing a disturbance compensation gain, a novel composite controller is proposed to counteract the “mismatched” lumped disturbances from the output channels. The proposed method significantly extends the applicability of the DOBC methods. Rigorous stability analysis of the closed-loop system with the proposed method is established under mild assumptions. The proposed method is applied to a nonlinear MAGnetic LEViation (MAGLEV) suspension system. Simulation shows that compared to integral control method, the proposed method provides improved disturbance rejection performance and robustness against load variation.