It presents a feedforward control strategy based on linear time-invariant disturbance observer for nonlinear controlled objects. At first, choose a linear time-invariant model as target model which have a desired dynamics. And then describe the non-linear properties of the controlled object as an equivalent input disturbance variable of the target model, which can be extended as state variables, so that the target model with the disturbance becomes the substituting model of the controlled object. Thirdly, design an observer of the substitute model to get the estimated value of the disturbance variables. Finally, a feedforward control can counteract the influence of the disturbance on the controlled object. The design theories of this method are confined within the architecture of linear system theory, and independent of the mathematical model of the controlled objects. Particularly, the controller is without any nonlinear part. In circumstances of reversible controlled object, the existence theorem of the substituting model is proved. At last, for the identical discrete time controlled object, comparative simulation research is performed between this control method and a nonlinear internal model control based on support vector machine ?th-order inverse system method. The simulation results indicate that the method proposed in this paper is better in linearization, anti-disturbance capability and system robustness.
