Research On Automatic Flight Control Law For The Jumbo Jet

Automatic flight control system is an essential part of the Jumbo Jet, and control law design isone of the key technologies. This paper mainly focuses on methods of automatic flight control lawdesign for the Jumbo Jet in normal flight conditions, and the integrated numerical simulationverification of entire flight process is carried out.Firstly, domestic and foreign research status of the transport aircraft’s flight control law designmethods is analyzed. On the basis of relevant airworthiness regulations and national standards,relevant design codes, flying quality requirements and specific performance index requirements ofautomatic flight control law design is summarized. Through researching on some kinds of domesticand foreign mature aircraft typies, the Jumbo Jet’s automatic flight mode used in this paper isconfirmed.Secondly, using data of Boeing707, the nonlinear mathematical model of six-freedom isestablished. For each flight phase, the appropriate trim points are selected. By trim and linearization,the linear models near each trim point are obtained. Based on linear models and nonlinear modelsrespectively, the system’s nature characteristic which includes stability and maneuverability and so onis analysed.Thirdly, control strategy of each automatic flight mode and overall control structure diagram ofeach flight phase are presented and the classical method is used to design control laws of the JumboJet’s each automatic flight mode. Digital simulation results based on nonlinear model show that all thedesigned control laws can meet the requirements of performance index and the designed controlsystem has certain capacity of anti-gust turbulence.Fourthly, based on LQR optimal control method and state feedback H robust control method,the inclined attitude control law of approach and landing phase is redesigned. The two kinds ofmodern control methods and classical PID control method are compared. A comprehensivecomparison of command trace characteristic and anti-crosswind disturbance performance shows thatthe overall control effect of state feedback H robust control method is the best, followed by theLQR optimal control method, and the PID control method is relatively worse.Finally, a nonlinear numerical simulation of the entire airspace flight process is carried out. Thesimulation results show that during the entire flight process, the designed automatic flight control lawscan meet the requirements of design specifications and performance index, and improve safty andcomfort of the automatic flight process.