Structural design of composite nonlinear feedback control for multivariable systems with input saturation

This paper investigates the design of the composite nonlinear feedback (CNF) control law for multivariable linear systems with input saturation. In the existing design procedure of the CNF control for multivariable systems, the nonlinear function is given by an m dimensional matrix in a diagonal form, where m is the number of system inputs. However, the inputs and the outputs of the system are coupled heavily in many cases. Thus, it is very difficult to tune the nonlinear functions of the diagonal matrix in the design of the CNF control. This paper proposes a more efficient design procedure for the CNF control by using the structure information of the system in a special coordinate basis (SCB) form. The proposed design procedure gives a clear map on how to select the structure of the nonlinear feedback gain, and how to tune the nonlinear functions in the CNF control.