Output-feedback adaptive stabilization for nonlinear systems with unknown direction control coefficients

This paper investigates the problem of output-feedback adaptive stabilization control design for a class of nonlinear systems with unknown direction control coefficients. By introducing novel input scaling transformations, the unknown control coefficients can be lumped together such that the original system becomes a new system and make the output feedback control design possible. After the introduction of an observer and estimator for state and parameter estimates, respectively, a constructive design procedure is given for the output-feedback adaptive stabilization control based on integrator backstepping. It is shown that, under some conditions, the controller designed ensures the state and the estimation error of the closed-loop system asymptotically converge to zero, while other closed-loop signals are uniformly bounded.