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

摘要

This thesis considers the problem of designing gain scheduled flight control system(FCS) for large transport aircraft that satisfy handling qualities criteria. The goal isto design a set of local Linear Time Invariant (LTI) controllers to cover the wide non-linear aircraft operation flight envelope from the viewpoint of the handling qualitiesassessment. The global gain scheduler is then designed that interpolates betweenthe gains of the local controllers in order to transfer smoothly between differentequilibrium points, and more importantly to satisfy the handling qualities over theentire flight envelope. The mathematical model of the Boeing 747-100/200 aircraftis selected for the purpose of the flight controller design and handling qualities as-sessment.In order to achieve an attitude hold characteristic, and also improve the dynamictracking behavior of the aircraft, longitudinal pitch Rate Command-Attitude Hold(RCAH) controllers are designed as the local flight controllers at the specific equilib-rium points in the flight envelope by means of a state space pole placement designprocedure.The handling qualities assessment of the aircraft is presented, based on which thescheduler is designed. A number of existing criteria are employed to assess the han-dling qualities of the aircraft, including the Control Anticipation Parameter (CAP),Neal and Smith, and C∗ criteria. The gain scheduled flight controller is found tohave satisfactory handling qualities.The global gain scheduler is designed by interpolating the gains of the local flightcontrollers in order to transfer smoothly between different equilibrium points, andmore importantly to satisfy the handling qualities over the flight envelope.The main contribution of this research is the combination of the gain schedulingtechnique based on the local controller design approach and handling qualities as-sessment. The controllers are designed based at a number of operating points andthe interpolation between them (scheduling) takes place through the schedulingscheme functions. The aircraft augmented with gain-scheduled controller performssatisfactorily and meets the requirement of handling qualities. Moreover, the per-formance using the gain-scheduled controller is considerably improved compared tothe performance using the fixed one.