Design of tracking control laws using nonlinear aircraft models

For advanced fighter aircraft, a broad spectrum of requirements and specifications have being achieved by designing advanced airframes and propulsion which feature low-signature shaping, composite materials, unconventional control surfaces, three-dimensional thrust-vectoring, etc. Aircraft must ensure desired mission-specific flight abilities and handling capabilities which are assessed by agility, controllability, maneuverability, robustness, stability and other performance characteristics, estimates and measures. The aforementioned performance and capabilities metrics can be ensured by designing flight control systems. This task implies multi-objective optimization and robust control for a given airframe and control schemes. Consistent, coherent and cohesive design methods must be applied with a minimum level of simplifications and assumptions. Flight vehicles are highly nonlinear. In general, linearization, decoupling and decentralization cannot be applied in expanded flight envelopes. We apply and use a nonlinear model to design robust control laws. The state transformation method is used to design tracking control laws which ensure near-optimal longitudinal and lateral dynamics. The design-specific performance functionals are minimized. We coherently examine the role of nonlinearities, including control bounds. It is illustrated that near-real-time design, adaptation and reconfiguration can be accomplished. These features are of a particular importance to potentially accommodate control surface or airframe damages and failures. It is illustrated that adaptation and reconfiguration can be achieved in realistic flight scenarios and close-in high-g engagements in an expanded operating envelope if the vehicle remains to be controllable and stabiliazable. Nonlinear simulations and data-intensive analysis are performed. Numerical results and quantitative analysis are reported in sufficient details for various flight conditions, envelopes and flight scenarios.