Output tracking of nonlinear systems with unknown control coefficients and nonlinear parameterization

A robust adaptive state feedback controller is designed for a class of nonlinear systems with unknown time-varying virtual control coefficients, uncertain time-varying nonlinear parameters and uncontrollable unstable linearization, by employing the Nussbaum-type gain technique and the adding a power integrator design. The controller can ensure all the signals of closed-loop globally uniformly bounded. Especially, the output tracking error is bounded. The proposed design method does not require any a priori knowledge of the unknown control coefficients except for their bounds. Moreover, only the information of a prescribed reference signal is used but neither its derivatives, nor itpsilas bound. In the end, the scheme is verified by a simulation example.