Robust control law design for lateral-directional modes of an F-16/MATV using μ-synthesis and dynamic inversion

Abstract

A manual flight control system for the lateral-directional dynamics of a modern fighter aircraft incorporating thrust vectoring is presented. Design goals are posed in terms of maintaining acceptable flying qualities during high angle of attack (α) manoeuvring while also achieving robustness to model parameter variations and unmodelled dynamics over the entire flight envelope. The need for gain scheduling a dynamic controller is eliminated by using an inner loop dynamic inversion/outer loop structured singular value (μ)-synthesis control structure which separately addresses operating envelope variations and robustness concerns, respectively. Performance objectives are based on commanding sideslip angle and stability axis roll rate. Realistic representations of both structured (real parametric) and unstructured uncertainty are included in the design/anlysis process. A flight condition dependent control selector maps generalized controls to physical control deflections, considering actuator redundancy, effectiveness and saturation issues. An angle of attack dependent command prefilter shapes commands to produce desired responses. Structured singular value analysis, low-order equivalent system (LOES) fits, and linear step responses demonstrate satisfaction of design goals. Simulation shows excellent control at both low and high angles of attack. © 1997 John Wiley & Sons. Ltd.