Designing Robust Large Envelope Flight Controllers for High-Performance Aircraft

Abstract

A simple two-degree-of-freedom control architecture and recent advances in MIMO H-infinity parameter-space control design are combined to form a new method of designing large envelope flight controllers for high performance aircraft. The procedure enables the designer to explicitly define the desired closed-loop dynamics and guarantees that the closed-loop provides robust stability and robust performance, which are defined using MIMO H-infinity specifications. The result is a straightforward procedure that enables the design of a robust flight controller that "forces" the closed-loop dynamics to behave like the specified 'desired dyamics' despite disturbance, modeling uncertainties, and variations in aircraft dynamics due to changing flight conditions. Te procedure is presented by designing an LTI pitch-rate controller for the F-16 Variable Stability In-Flight Simulator Test Aircraft (VISTA). Linear and nonlinear simulations show that the LTI controller provides predicted 'Level 1' flying qualities throughout the large design flight envelope.