Gain scheduling for a passenger aircraft control system to satisfy handling qualities

This thesis considers the problem of designing gain scheduled flight control system \n(FCS) for large transport aircraft that satisfy handling qualities criteria. The goal is \nto design a set of local Linear Time Invariant (LTI) controllers to cover the wide non- \nlinear aircraft operation flight envelope from the viewpoint of the handling qualities \nassessment. The global gain scheduler is then designed that interpolates between \nthe gains of the local controllers in order to transfer smoothly between different \nequilibrium points, and more importantly to satisfy the handling qualities over the \nentire flight envelope. The mathematical model of the Boeing 747-100/200 aircraft \nis selected for the purpose of the flight controller design and handling qualities as- \nsessment. \nIn order to achieve an attitude hold characteristic, and also improve the dynamic \ntracking behavior of the aircraft, longitudinal pitch Rate Command-Attitude Hold \n(RCAH) controllers are designed as the local flight controllers at the specific equilib- \nrium points in the flight envelope by means of a state space pole placement design \nprocedure. \nThe handling qualities assessment of the aircraft is presented, based on which the \nscheduler is designed. A number of existing criteria are employed to assess the han- \ndling qualities of the aircraft, including the Control Anticipation Parameter (CAP), \nNeal and Smith, and C∗ criteria. The gain scheduled flight controller is found to \nhave satisfactory handling qualities. \nThe global gain scheduler is designed by interpolating the gains of the local flight \ncontrollers in order to transfer smoothly between different equilibrium points, and \nmore importantly to satisfy the handling qualities over the flight envelope. \nThe main contribution of this research is the combination of the gain scheduling \ntechnique based on the local controller design approach and handling qualities as- \nsessment. The controllers are designed based at a number of operating points and \nthe interpolation between them (scheduling) takes place through the scheduling \nscheme functions. The aircraft augmented with gain-scheduled controller performs \nsatisfactorily and meets the requirement of handling qualities. Moreover, the per- \nformance using the gain-scheduled controller is considerably improved compared to \nthe performance using the fixed one.