Sliding mode control with an extended disturbance observer for a class of underactuated system in cascaded form

Abstract

A sliding mode controller based on an extended disturbance observer is investigated to control a class of underactuated system in this paper. By using strict feedback technique, the underactuated system is presented as a special cascade form. First, an extended disturbance observer is designed to estimate the unknown external disturbances and model uncertainties of the underactuated system. Furthermore, a sliding mode control strategy is proposed to stabilize the underactuated part directly and drive the variables to the sliding mode surface. Finally, combining the sliding mode controller with the extended disturbance observer, a sliding mode controller with disturbance observer is designed. The stability of the overall system is proved and a numerical example is presented to illustrate the effectiveness of the proposed disturbance observer and controller.