Output feedback stabilization of systems with nonlinearity of unmeasured states

This paper deals with global stabilization of a class of nonlinear dynamic systems using output feedback. The systems considered in the paper have nonlinear functions of unmeasured state variables, in addition to nonlinear functions of the system outputs. A nonlinear reduced order observer is proposed to estimate the unknown system state in the system. Estimated state variables are used for control design, together with the system output. Certain conditions are identified for the proposed observer and control design. Under those conditions, the proposed control design ensures the global stability of the closed-loop control system.