Lateral control design for the Cessna Citation X with robustness and handling qualities requirements

Satisfying handling qualities remains one of the major concerns of flight control engineers. In addition to satisfy many stringent performances, flight control systems have to be robust to various uncertainties. Although... [ view full abstract ]

Satisfying handling qualities remains one of the major concerns of flight control engineers. In addition to satisfy many stringent performances, flight control systems have to be robust to various uncertainties. Although modern control techniques can handle many types of constraints, fulfilling these requirements still remains a challenge for engineers. In this paper, a lateral flight control design methodology that satisfies handling qualities requirements and robustness is presented. The Flight Control System consists of two subsystems; a Stability Augmented System (SAS), which improves the aircraft stability, and a Command Augmented System (CAS), which controls the entire system. The methodology was divided in two steps. The first step consisted in obtaining a first flight control system that satisfies a set of criteria in frequency and time domains. A combination of the optimal control theory and the guardian maps approach was used to find a lower order controller (for both SAS and CAS) that guarantees all the performances desired for the closed loop. The next step concerned the robustness of the flight control system. Using the guardian maps approach, several analyses were done to verify if the closed loop was robust to variations dues to uncertainties in terms of mass and center of gravity position variations. Finally, a Genetic Algorithm was used to automatically tune the controller gains. Simulations for more than 100 flights conditions have been performed using a full nonlinear aircraft model of the Cessna Citation X that is the fastest business aircraft.