Sliding Mode Control for a Class of Fractional-Order Nonlinear Systems Based on Disturbance Observer

摘要

In this paper, a sliding mode control scheme is proposed for a class of fractional-order nonlinear systems in the presence of external unknown disturbances. To handle unknown bounded disturbances, a fractional-order sliding mode disturbance observer (SMDO) is explored for the fractional-order nonlinear system (FONS). The designed disturbance observer can approximate the disturbance well and the estimate error is convergent by appropriately choosing the design parameters. On the basis of the developed fractional-order SMDO, a sliding mode tracking control scheme is further studied. Under the proposed control scheme, the tracking errors between output signals and desired signals converge to the origin. Finally, numerical simulation results further demonstrate the effectiveness of the proposed tracking control scheme for the FONS subject to external unknown disturbances.