Composite adaptive fuzzy H? tracking control of uncertain nonlinear systems
In the H? tracking-based adaptive fuzzy controllers (HAFCs) of perturbed uncertain nonlinear systems, additional H? control terms would greatly degrade fuzzy approximation abilities, which violates the original intention of using fuzzy logic systems. To solve this problem, a composite HAFC (CHAFC), which combines the HAFC with composite adaptation technique, is proposed in this paper. Outside of the approximation region, a robust stabilization controller is developed to achieve semi-global stability of the closed-loop system. Within the approximation region, a seriesparallel identification model is introduced into an indirect HAFC to construct a CHAFC that can simultaneously achieve fuzzy identification and H? tracking control. It is proved that the closed-loop system obtains H? tracking performance in the sense that both tracking and modeling errors converge to small neighborhoods of zero. Simulated applications of aircraft wing rock suppression and inverted pendulum tracking demonstrate that the proposed approach not only effectively solves the aforementioned approximation problem, but also obviously outperforms previous approaches.
composite adaptation h? tracking control adaptive fuzzy control fuzzy identification