Research On Flight Simulator Motion Platform Control System Based On Quantitative Feedback Theory

Flight simulator is a kind of emulation vehicle that can simulate aircraft flying in the sky and moving on the ground. Comparing with training driver by using real airplane and flying experiment, flight simulator has an advantage in security, indestructibility, and non-pollution. Six-freedom motion system plays an important role in all composing parts of flight simulator, and it is actually a six-freedom instantaneous overload-simulating vehicle which is controlled real time by computer. So the performances of motion simulating system directly relate with fidelity of flight simulating, and the research of flight simulating system about control strategy is one of the key technologies of improving motion performance of flying simulator. Therefore, research for control strategies of flying simulating system and designing reasonable controller have the very important meaning.After synthesizing numerous related literatures and reference materials at home and abroad, the outline and current trend of domestic and oversea flight simulator is summarized in this paper, and characteristics, state-of-the-art of all kind of key issues of flying simulator 6-DOF moving simulation system is summarized. At the same time applications of six-freedom motion platform in other fields is introduced briefly.In this paper, kinematics characteristics of 6-DOF motion platform are studied by using analysis method of matrix and vector. Detailed analysis of forces received by motion platform is done by using Newton-Euler and Lagrange methods synthetically. Force equilibrium equations of motion system upper platform are built based on d'Alembert Principle and reduction method, and a task-workspace dynamic equation of motion platform is established by using Kane method. A joint-workspace dynamic equation is established,and the coupling between channels is classified. The acceleration coupling between channels evaluating index are built, based on which the acceleration coupling between channels of flight simulation test prototype is analyzed quantitatively, and which provide with a better basis for design of motion platform structure and evaluation of coupling between channels.In this paper, the mathematical model of single channel of 6-DOF motion system is established, and the influence of model parameters upon the system performance is analyzed. The single channel state space closed-loop mathematical model and general stochastic state space grey-box identification model are set up, and the criterion function for model parameters identification is defined, and the mathematical models for Jacobian matrix and gradient matrix of the criterion function are established.A kind of three-dimensional mutually non-correlative exciting signals generator is designed, and the closed-loop identification experiment of motion platform is done. The model parameters are identified by using predicted-error method, which is based on the LM algorithm used for the criterion function optimization. The state space identification model outputs are compared with the real system outputs under the effect of the same input signal, and the comparison results show that the close ratio is over 70%, which proves that the model parameters identified in this paper are reasonable.In accordance with flight simulator's demand of motion simulation system motion performance, the electro-control part of flight simulation test prototype is reconstructed in this paper. At the same time the flight simulation control software is designed by using VC++ language and RTX real time extensive system. Based on the control system designing performance index demand of the flight simulation test prototype and the single channel identification model, a kind of 2-DOF QFT robust controller is designed by using quantitative feedback theory. Simulation and experiment researches on the 6-DOF motion system are performed based on the control system designing index demand. Research results show that the 2-DOF robust controller can compensate perfectly the influence on system performance caused by asymmetrical characteristic of power mechanism, and has the very strong ability of resisting the load coupling between channels and the strong robustness for parameters time-varying characteristics and non-modeled dynamic characteristics, which satisfies all designing performance index demand prescribed before. At the same time the research results prove that the electro-control system and control software of the test prototype designed in this paper are successful, and the theories and views set forth are right, and the model identification algorithm and the controller designed are reasonable and feasible.