Research On Fly-by-wire Flight Control System Design Technology For Large Aircraft

As the top level product of aviation industry,large aircraft plays an important role in high-tech industry with national strategy.Large aircraft program will have historical impact on China’s future society,economy and the advancement of the scientific technology as a whole in particular.Fly-by-wire flight control technology,as the core of flight control system,is an important enabling technology,which can assure the safety,improve the reliability and update comfort for large aircraft.To satisfy the requirements of safety and airworthiness for FBW flight control system(FCS)of large aircraft,the architecture for large aircraft FBW FCS is researched methodologically.The nonlinear mathematic model of typical large aircraft is established and the characteristic of this plane is analyzed,which lays the foundation of the following study on FCS.Three crucial technologies,namely redundant system design,flight control computer design and control law design,are researched.Design methods guide the design of FCS,Flight control computer and control law.The results of digital simulation and analysis demonstrate that such methods are feasible.The main innovative points of this dissertation are listed as following:(1)The architecture research on large aircraft FBW flight control system design consists of three parts: mission requirements,system structure,and supporting technology.The required functions are analyzed to meet system requirements.The tendency of FBW flight control system structure is presented.The research results of design criteria,standards,tools,methodologies and development procedure provides powerful technical guidelines for FBW flight control system study and design.(2)According to the high safety requirement for large aircraft FBW flight control system,FBW flight control system redundant design procedure is presented.Taking aileron control as an example,system redundant design is complemented based on safety analysis,including all level safety requirement analysis,system redundant configuration,redundancy structure definition of aileron control system,PSSA analysis and redundant structure design.Simulation analysis and calculation results show that system design satisfies the safety requirements,and there are outstanding effect on system fault tolerance,system redundant configuration and voting / monitoring plane setting as well.(3)FBW flight control computer,as a pivotal component,has been researched to satisfy high reliability requirement.Dissimilar redundancy design technology and self-monitoring technology are researched.FBW flight control computer fault tolerant scheme is presented for a large aircraft.The reliability analysis model is used to calculate the basic reliability and mission reliability for this computer,results shows that the safety requirements of flight control computer are satisfied.The application of self-monitoring boosts up the ability of fault isolation.Message sharing mechanism for the function modules is built by backplane bridging technology and the primary flight control computer with module reconfiguration is designed,which can make flight control system mission reliability increase one order of magnitude in the same condition of hardware resource.(4)General multi-effector control strategy based on online identification and general multi-effector control strategy based on mission modes are presented in the light of large aircraft multi-effector configuration characteristics and safety requirements.The control command design methods are studied.Applying modern control methodology to flight control law design is concentrated on.Firstly,two kinds of promising methods—dynamic inversion design and eigenstructure assignment design,as well as their robustness enforcement method are studied.Robust eigenstructure assignment control law for pitch control and dynamic inversion control law for lateral control are designed and simulation results show that such control laws meet the requirements for stability margin and flying qualities.Then,L1 adaptive controller under the constraints of servo actuator is studied and the pitch control law is designed.The simulation results show that the algorithm is effective.