Internal-Model Disturbance Rejection for Nonlinear Systems via Full-States Linearization

The paper considers the controller design problem of disturbance rejection for nonlinear systems under external persistent disturbance by using the full-state linearization approach. The disturbance rejection controller with nonlinear term is designed, in which the nonlinear control term cancels the open-loop nonlinearity. According to the internal-model principle, the internal-model compensator is constructed which has the same dynamical characteristic with disturbance. The optimal regulator of the augmented system is designed by using Pontryagin minimum principle. Then the nonlinear disturbance rejection controller based on internal model is obtained, in which the internal-model compensation control term cancels the effect produced by disturbance. Comparing with the nonlinear feedforward and feedback disturbance rejection controller, the designed nonlinear internal-model-based disturbance rejection controller can eliminate eliminating the nonlinearity and rejecting disturbance with zero steady-state error.