Trajectory Tracking and Disturbance Rejection for Euler-Lagrange Systems with High-Order Actuator Dynamics*

In this paper, we study the trajectory tracking and disturbance rejection problem of a class of Euler-Lagrange (EL) systems with high-order actuator dynamics. This type of EL system takes into account not only the dynamics of the rigid component of the plant but also the dynamics of the actuators. Thus, the trajectory tracking and disturbance rejection problem for this type of EL system poses some specific challenges. Assuming that the disturbance is a multi-tone sinusoidal function, we first establish a nonlinear observer for the unknown disturbance based on the internal model principle. Then, we propose a control law through a backstepping-like design procedure for the EL system to solve the problem. A numerical example is provided to demonstrate the efficacy of the proposed approach.