Nonlinear Disturbance Observer-Based Dynamic Surface Control of Mobile Wheeled Inverted Pendulum

In this brief, a dynamic model of a mobile wheeled inverted pendulum (MWIP) system is improved considering friction forces, and a nonlinear disturbance observer (NDO)-based dynamic surface controller is investigated to control the MWIP system. Using a coordinate transformation, this non-Class-I type underactuated system is presented as a semistrict feedback form, which is convenient for dynamic surface controller design. A dynamic surface controller together with an NDO is designed to stabilize the underactuated plant. The proposed approach can compensate the external disturbances and the model uncertainties to improve the system performance significantly. The stability of the closed-loop MWIP system is proved by Lyapunov theorem. Experiment results are presented to illustrate the feasibility and efficiency of the proposed method.