Flight Simulation Modelling And Software Development For Flight Simulator

Flight simulator simulates flight realistically on ground. Though it is essential to the aviation industry, our nation falls much behind other countries on the technique of flight simulator development. The study of key technique on flight simulator is emergent, for our government has decided to promote project of big aircraft. Flight simulation system is the core system of flight simulator, which determines the level of quality. It works out the states of aircraft and drives virtual reality equipments based on the configuration of instructor and manipulation of pilots. It is a challenging work to model and simulate a modern aircraft, for it usually owns complex structural dynamics and aerodynamic characters. The study of this paper will implement the function of flight simulation system by building a flight simulation model with high fidelity and develop a software program with clarity, perception and convenience of maintenance.To achieve this purpose, the flight movement equations in the rotating ellipse earth have been deduced firstly. Because the flight dynamic equations in actual commercial flight simulator are on the assumption of inertial flat earth, the accurate earth geodetic model coordinating with advanced navigation equipment and global topography database will improve the fidelity of flight simulation and make it vivid. Then the aerodynamic model is developed according to a specified aircraft. The precision of linear interpolation and cubic interpolation is compared for test design. The simulation result has been verified by conforming to flight test data.Secondly, dynamics of landing gear touching ground is analyzed and modeled to simulate aircraft ground handling characters. Because landing gear model in actual commercial flight simulator is not suit non-horizontal runway surface and can not simulate runway excitation, landing gear shimmy and brake-induced vibration which may lead to accidents, in this paper, an improved collision detection block and new deflection computed method which considers virtual runway excitation are introduced to obtain vertical force of the tire acted by ground. Then the cornering force and braking force on tire are worked out through velocity of tire with respect to ground. This developed landing gear model owns the capability of reflecting high fidelity of aircraft ground handing characters, which are validated by the comparison of simulation and flight test results showing energy absorbing ability, turning ability and braking ability.Thirdly, the trim method of flight simulation model is analyzed and designed. Because the trim method in actual flight simulator is based on pattern search which may lead to trim failure for being trapped in local optimum, this paper introduces an elite re-optimized hybrid genetic algorithm which mixes pattern search and classical genetic algorithm. Pattern search is used to re-optimize the elites of a group of population to increase the fitness of the population but not break individual variety. This method is validated by actual test which shows the ability of avoiding trapped in local optimum, the effectiveness to reduce iteration loops and the precision improvement of final result.Fourthly, the code of flight simulation system and trim method is realized based on object oriented programming technology. Because the software in actual commercial flight simulator is usually developed by procedure-oriented programming method which makes the software hard to understand and maintain, this paper introduces the object oriented practice for flight simulation software development. The whole sub models derive directly from a parent class so they have a unify interface. These sub models aggregate in some sub system which can form a linked list after they are instantiated. The hierarchy mode of these simulation models reduces risk of development and difficulties of maintenance and can make the software use in different environments.Finally, the software is executed in the flight simulator composed of PCs. Then the accuracy of flight simulation model, the suitability of trim method and the advantage of object oriented programming are validated in this simulator. This simulator is advantageous in the cost to the products of foreign companies which are often developed by their own architectures, for the simulator is composed of popular PCs and the development tools are mature business software. So this work is benefit to simulator home-made and can avoid the disadvantage of our weak technology and acknowledge accumulation.