Exponential Tracking and Disturbance Rejection for Euler–Lagrange Systems With High‐Order Actuator Dynamics

ABSTRACT In this paper, we study the exponential 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 components of the plant but also the dynamics of the actuators and it includes the elastic joint robot manipulator as a special case. Assuming the reference signal is bounded with bounded derivatives and both the output and the input of the actuator are subject to multi‐tone sinusoidal disturbances, we first establish nonlinear observers for the unknown disturbances based on the internal model principle. Then, we further construct a control law through a backstepping‐like design procedure to achieve the exponential tracking and disturbance rejection for the class of EL systems with high‐order actuator dynamics. A numerical example is provided to illustrate the proposed approach.