Controller design for nonlinear systems with disturbances and noises via double coordinate transformations

The design of robust controllers for a class of SISO nonlinear systems in the presence of disturbances and noises is presented. In this paper, the concept of double coordinate transformations is proposed and is used as a technique to robustify the cancellation of the disturbance and noise terms by means of two on-line adjustable parameters. Bounds for the adjustable parameters are given to ensure the robust stability of the controlled system. The major advantage of this proposed method is that the disturbances and noises need not be completely measured. The performance characteristic of the proposed method is illustrated through an example of a CSTR system. The simulation shows the results in satisfactory control.