For a class of strict feedback nonlinear system

a nonlinear adaptive controller was first investigated.The design procedure used backstepping method based on DBFNN (Direction Basis Neural Network).In each step of backstepping a virtual controller was designed by introducing a suitable Lyapunov function.In the last step the singular-free real controller was synthesized.The tuning law of NN weights was derived from the selected integral Lyapunov function.So the stability of the closed loop can be guaranteed. Then the proposed scheme was applied to design an excitation controller for one power system with unknown disturbance and unknown parameters.The simulation shows the validity of the proposed method.