Optimization for flight control system with constraints supplemented handling qualities

Abstract

To evaluate performances of the flight control system of high-fidelity aircrafts, criteria specified by MIL-STD-1797A and MIL-F-8785C should be applied. In order to apply the criteria, a low order equivalent system has to be determined. In this study, the direct method including evaluation criteria of handling qualities as optimization method’s constraints are carried out to complement problems of the indirect method that assesses whether a flight control system designed by existing optimization techniques satisfieshandling qualities or not. For the direct method, the Co-Evolutionary Augmented Lagrangian Method (CEALM) is used. Neal-Smith criterion, short-period flying qualities, phugoid stability, bandwidth criteria, and Control Anticipation Parameter (CAP) are used as handling qualities assessment standards. F-16 longitudinal flight control system is performed the optimization with the performance index and constraints. After performing the optimization, designed control system is verified how many constraints satisfy. If some constraints are not satisfied, i.e. constraint conflict occur, an optimization is executed again except some constraints. Then, it is investigated that removed constraints affect performances of the flight control system. Moreover, present optimization technique can optimize flight condition one by one. In case of performing optimization for several flight conditions, it should be executed as many times as flight conditions. Although reliability of the optimization result can be high in that case, it is required considerable time for the optimization. To solve this problem, an optimization method is constructed with gain scheduling. Then we study techniques that have lower reliability about performances than one of the former but computation time is able to abridge.