Trajectory Tracking Control of Nonlinear Singularly Perturbed Systems With Disturbances

In order to solve the control problem of singularly perturbed systems subject to external disturbances, a novel composite control scheme based on the disturbance observer and the singular perturbation technique is proposed. To reduce the system order and facilitate the controller design, the singular perturbation technique is first utilized to de-compose the original high-order system into two lower order subsystems. Subsequently, nonlinear disturbance observers are proposed for reduced order slow subsystem and the reduced order fast subsystem respectively. Using the estimated disturbance information, two composite controllers are developed for the reduced-order subsystems, and the uniformly ultimately boundedness of subsystems is guaranteed. Moreover, the stability of the closed-loop high-order system is also proved via the Lyapunov approach, even though the observers and controllers are developed for the reduced-order subsystems. The effectiveness of the proposed control scheme is demonstrated by simulations.