Semi-global practical stabilization for a class of second-order uncertain nonlinear systems

This paper investigates the semi-global practical stabilization for second-order nonlinear systems subject to unknown control coefficients and completely unknown nonlinear function. In order to achieve the control objective, a state feedback controller is firstly constructed to ensure that systems under consideration satisfy uniform Lyapunov property. Then, based on output feedback domination method, we skillfully introduce a reduced-order observer to estimate all the unmeasurable states. Finally, a continuous output feedback controller that is based on saturated state estimate is constructed to ensure the semi-global practical stabilisation for the second-order uncertain nonlinear systems. With the help of a suitable simulation example, the design process is effectively demonstrated.