Adaptive fuzzy mixed H2/H∞ lateral control of nonlinear missile systems

An adaptive fuzzy mixed H₂/H_∞ lateral control of nonlinear missile systems with uncertain disturbances considered is proposed to achieve H₂ quadratic tracking with H_∞ disturbance rejection. This approach can be applied to control the lateral directional dynamics of the missiles at high angle of attack or generate moments on missile operating in flight regimes where the effectiveness of conventional aerodynamic surfaces is reduced. Using an adaptive fuzzy approximation method, the uncertain nonlinear model of the missile system is estimated. Then, by a mixed H₂/H_∞ control design, the effects of external disturbance and fuzzy approximation error as well as consumed energy of the controller is minimized. By the skew symmetric property of the missile system and adequate choice of state variable transformation, this problem can be reduced to solve two algebraic Riccati-like equations. Furthermore, a closed-form solution to these two algebraic equations can be obtained with very simple form for the preceding control design.