The main objective of the current investigation is to provide a simple procedure to select the controller gains for an aircraft with a largely wide complex flight envelope with different source of nonlinearities. The stability and control gains are optimally devised using genetic algorithm. Thus, the gains are tuned based on the information of a single designed mission. This mission is assigned to cover a wide range of the aircraft’s flight envelope. For more validation, the resultant controller gains were tested for many off-designed missions and different operating conditions such as mass and aerodynamic variations. The results show the capability of the proposed procedure to design a semiglobal robust stability and control augmentation system for a highly maneuverable aircraft such as F-16. Unlike the gain scheduling and other control design methodologies, the proposed technique provides a semi-global single set of gains for both aircraft stability and control augmentation systems. This reduces the implementation efforts. The proposed methodology is superior to the classical control method which rigorously requires the linearization of the nonlinear aircraft model of the investigated highly maneuverable aircraft and eliminating the sources of nonlinearities mentioned above. 1. Introduction Due to stringent performance and robustness requirements, modern control techniques have been widely used to design the flight control systems ( ). However, researchers have been facing the difficulties of the complex nature and the nonlinearity strength embedded in the aircraft’s dynamical model. For example, inertia coupling and attitude representations (Euler angles representation or quaternion representation) of the aircraft rigid body motions require nonlinear mathematical models [1]. Special impact on aircraft model comes from the nonlinear aerodynamic submodel such that aerodynamics coefficients significantly change with operating conditions. This leads to a significant change in the stability and performance of the aircraft dynamics. In addition, many other sources of nonlinearities appear in actuator nonlinear subsystems, sensor nonlinear subsystem, and engine nonlinear subsystems. In order to address the designing FCS, gain scheduling, one of the popular methodologies to design controllers for nonlinear systems has been adopted to design stability augmentation system (SAS), and control augmentation system (CAS) [2–4]. In the conventional gain scheduling approach, the nonlinear system is linearized at several equilibrium operation conditions. Local linear
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