Fixed Structure Flight Control Design of an Over-actuated Aircraft in the Presence of Actuators with Different Dynamic Performance

This paper presents the application of an H∞ control technique to the control of a HAPD (High Altitude Performance Demonstrator) aircraft having redundant surfaces. The interaction of the controlling moments and forces with the aircraft flexible modes requires a careful use of the control resources in the frequency domain also considering that aerodynamic surface deflections are limited in amplitude and angular rates. A fixed structure H∞ control problem design, inspired by the classical minimum norm allocation control approach, is formulated and solved in terms of Linear Matrix Inequalities. Numerical simulations on the full nonlinear model of the HAPD including flexibility modes are carried out to show the effectiveness of the proposed technique on the whole flight envelope which is covered using a parameter dependent formulation of the linearized model plants.