Research On Fault Diagnosis For Electro-Mechanical System Of Civil Aircraft

The theoretical research on fault diagnosis for electro-mechanical system is made in this thesis by exploring the application of integrated fault diagnosis technology to multi-system on system level. The research is focused on the structure of integrated fault diagnosis system and the methods of fault diagnosis for electro-mechanical systems and electro-mechanical subsystem (Environment Control System, Landing Gear System, and Hydraulic System). Expert system based on fault tree and fault diagnosis verification platform are designed and implemented on the basis of the theory.During the research on the structure of integrated fault diagnosis, we determine the framework for integrated fault diagnosis system by using AFDX as the communication network in terms of low costs, light weight and the reliability, referring the structure of the advanced foreign aircraft B787 and combining with the characteristics and the development of civil aircraft.In the fault diagnosis of electro-mechanical subsystem, different fault diagnosis algorithms are used, according to the fault characteristics of subsystems. The heat exchanger of environmental control system uses parameter estimation methods, according to the corresponding characteristics of the model parameters and physical characteristics. The control component of environmental control system uses full-dimensional fault detecting observer, according to the typical failure mode. The landing gear system is divided into Electro-hydraulic servo valve and buffer system, and use full-dimensional fault detecting observer and the unknown input observer for fault diagnosis, according to the characteristics of the two parts. For the hydraulic system, as it is high nonlinear and it's difficult to establish accurate mathematical model, knowledge-based BP neural network is used for fault diagnosis.As the fault diagnosis expert system does not depend on the model and can reason based on knowledge, by using C++ Builder 6.0 and Access database as a development tool and combining fault tree and the method of expert system, the integrity knowledge acquisition bottleneck is solved. In the design of fault diagnosis verification platform, IEMS fault daignosis laptop, IEMS fault daignosis computer, IEMS integrated electro-mechanical computer and the simulation results are completed by distributed simulation technology, solving the interaction problem of the simulation model and software and network communication problems between the processor.