Though there is great development o

Though there is great development of intelligent control, in the above-mentionedmethods, the tuning of intelligent system is directly proposed with tracking error which means the controller is aiming at achieving asymptotic stability and tracking. However, the motivation of using intelligent system to approximate nonlinear functions was ignored, thus the accuracy of the desired identified models is out of attention. As a result, the tracking performance is difficult to evaluate since mostly only the tracking error can be guaranteed to be bounded. With the discussed concern, an interesting work is presented in [50] that the modeling error is included in fuzzy weight updating law. However, the method requires the nth derivative to be known thus it cannot be used in real application. To deal with this problem, the design with low-pass filter is proposed in [51]–[53] and better tracking performance is achieved with faster adaptation. Furthermore, in [8], the composite neural control is proposed for the strict-feedback systems by introducing new modeling error and more accurate tracking is achieved.