Research On Modelling Of Engine System Of Flight Simulator And Object-oriented Simulation

Flight simulator can safely and realistically reproduce the behavior of aircraft flying through the air, which is the indispensable simulation equipment for the development of new aircraft and flight training in aviation industry. While our country falls far behind the developed countries overseas in the development of flight simulator, especially, the high level flight simulator and technical storage. In the current background of our government promoting projects of developing large aircraft, carrying out research of key technologies of flight simulator and serving for the large aircraft development and flight training is imperative. Real time simulation model of the aircraft and airborne system are the main body of flight simulator. Aero-engine as the heart of airplane, its simulation model is the core of whole flight simulator, which directly determines the fidelity of flight simulation and qualification level of flight simulator. As for the aero-engine is not only a multi-variable, non-linear aerothermodynamics system, its working condition and work state are also complex and multivariable, so the modeling and simulation of engine and its control system is a very difficult and challenging task. This paper aims at establishing high-fidelity, real-time, complete model of engine and its control system, and developing a set of aircraft engine simulation software with clear structure, easy maintenance and is easy to expand, so can implement real time simulation of propulsion system of flight simulator.To achieve the purpose motioned above, firstly, it studied the characteristics which are applicable for the aero-engine model of flight simulation, and proposed basic modeling principle of simulation of engine and its control system, so it can give an effective guidance for the establishment of high-precision, real-time, expansibility and flexibility model of the propulsion system. Using similar theory and component level modeling method, it established the real time performance model of engine and its auxiliary system, including rotor dynamics, thermodynamic model, and models of sensors, actuators dynamics and valves dynamic. Compared to a simple static and dynamic performance simulation of the engine, the established model greatly expands the scope of simulation, promotes accuracy of simulation and satisfies requirements of the flight simulation. It established typical fault model of engine through constructing the fault factors on the basis of normal state model, which overcomes the complexity of fault models established with aerodynamic coupling principle and the sequential simulation technique. The established practical and simplified fault model not only improves the real time feature of simulation, but also realistically reproduced the fault performance, fault logic and effect, so can satisfy the requirements of the engine fault simulation of flight simulator.Secondly, it established function model of the aero-engine control system with modular technology and fine modeling method, studied the handling approach of improving simulation accuracy and real-time characteristic. Through the function decomposition of actual control system, it determined the relation of interface and composition structure of function model, established the function model of power management, fuel flow control, bleed flow control, limit control, thrust reverser control, start up logic and et al. Although the secondary features are simplified or ignored in the modeling process, the basic and important control functions for the implementation of the engine control are reserved intact. Simulation results of the control system demonstrate that function model of control system is effective.Thirdly, it established the simulation model of engine and its control system using object-oriented technology and application framework technology. In order to avoid the disadvantages of poor readability and maintenance caused by the traditional procedure-oriented programming method in the design process of large software, it proposed the method of connecting object-oriented technology with MATLAB to design the software of engine simulation system. According to the modeling route from "chief" to "sub" and hierarchical design patterns, it constructed generic hierarchy of real time simulation model and simulation model of propulsion system, and customized operation framework of simulation model of propulsion system. Inheritance, polymorphism, aggregation and associated mechanisms between object classes ensured that the simulation system has clear structure, good maintenance and is well-bedded and easy to expand. A unified operation framework not only enhances the modeling flexibility, but also achieves stable and high efficient operation of the simulation.Finally, it analyzed the connotation of simulation fidelity, constructed a multi-level evaluation system of engine simulation fidelity, and studied the quantitative validation and qualitative validation for the assessment of simulation fidelity. Objective quantitative validation, subjective qualitative evaluation and real time simulation validation of engine and its control system are carried out on the developed flight simulator with distributed simulation architecture. Results indicate that the mathematical model of the engine and its control system is accuracy and reasonable, and the object-oriented simulation model is practical and predominant. Compared with the large foreign companies developing flight simulator with specialized equipment, using current mainstream PC with mature business software has more cost advantages and flexibility, which has been an actively attempt and useful exploration for the home made of high level flight simulator in the future.