Adaptive fuzzy mixed H2/H∞ attitude control of spacecraft

This paper presents an adaptive fuzzy mixed H₂/H_∞ attitude control of nonlinear spacecraft systems with unknown or uncertain inertia matrix and external disturbances. Using an adaptive fuzzy approximation method, an uncertain nonlinear model is estimated. Then, by a mixed H₂ and H_∞ attitude control design, the effect of external disturbance and fuzzy approximation error on spacecraft attitude can be restrained and the tracking error as well as consumed energy of the controller is minimized. By virtue of the skew symmetric property of the spacecraft system and adequate choice of state variable transformation, this adaptive fuzzy control problem can be reduced to solving two algebraic equations instead of a pair of coupled time-varying differential equations. Finally, experimental simulation results are presented to demonstrate the effectiveness of the proposed design methods.