Nonlinear Disturbance Observer-Based Control for a Class of Port-Controlled Hamiltonian Disturbed Systems

In this paper, a composite control scheme is presented to asymptotically stabilize a class of port-controlled Hamiltonian systems under nonvanishing disturbances. First, based on the damping injection method and the nonlinear disturbance observer (NDOB) technique, the robust composite control strategy is designed. The NDOB, as an effective observation tool, is developed to estimate the disturbances, and furthermore, the disturbances can be feedforward compensated using the estimates of disturbances. Then, for the augmented system, an asymptotic stability theorem is proposed via an input-to-state stability technique and Lyapunov stability theorems. The proposed control approach exhibits not only good robustness and disturbance rejection performances but also the property of nominal performance recovery. Finally, a simulation example on a circuit system is given to show the feasibility and advantage of the composite control method.