Adaptive tracking of parametric strict-feedback nonlinear systems in the presence of additive disturbance

In this paper, we consider the same class of systems in a previous paper, i.e. a class of parametric strict-feedback nonlinear systems with additive disturbance. By using the backstepping technique, adaptive control algorithm is developed. Unlike the exiting control schemes for systems with additive disturbance, no knowledge is assumed on two time continuous differentiability of the disturbance. Also, the developed backstepping controller does not require that the uncertain parameters is restricted within a known interval. Furthermore, overestimation of the system parameters is removed by employing the tuning functions method. It is shown that the proposed controller not only guarantees global stability, but also asymptotic tracking.