Research And Realization On Robustness Analysis Of Flight Control Laws

High-quality control system design and application is the key point that affects the stabilization of the flight vehicle. So far, the frozen-coefficient method with small offset linear model is widely adopted in the traditional analysis and design method of flight control law that applied in engineering. Although engineering application certifies that this method could satisfy the flight control demand, this method still has evident drawbacks: the design results rely on the intuition and the experience of the research staff more or less, the analysis, validation and verification procedure during and after the design procedure are very tedious, and most of all, the stability issue cannot be theoretically interpretation perfectly.In view of the issues in the traditional analysis and design method, we make a systematic investigation of the domestic and external researches and technical development of robustness analysis of flight control laws. In order to reduce the investments and the costs and to improve the reliab of the results, the following researches have been carried out in this thesis:⑴After reviewing the Lyapunov stability theory, the increment stability theory and the contraction analysis method, we have proposed to describe and analyze the stability issue of dynamic system from a novel viewpoint of physics. By decomposing the first order differential of system state equation, we are able to understand and describe the stability of dynamic system more clearly.⑵SOS programming method is applied to study the ROA estimation issue, the V-S iterate method based on SOS programming is proposed, a number of examples were given to illustrate the estimation effects of SOS programming. Compared to the LMI method or the BMI method, the V-S iterate method based on SOS programming was more advantage in the simplicity of problem description and the consumption of computing time.⑶The LPV uncertainty modeling methods of aircraft been studied and full flight envelope grid quasi-LPV optimization modeling method based on matrix been proposed, this method can reduce the modeling error during the modeling procedure.⑷The characteristic points selection method been studied. The selection method based on contraction analysis and SOS programming is proposed, this method can avoid the irregular change of the equilibrium points caused by vary of uncertainty parameters when using the ROA estimation method, and can determine the uncertainty parameters’ upper bound, this made the characteristic points selection more systemically and more theoretical.⑸Small perturbation theory is applied to the noncircular cross section missile in engineering, the applicability and the feasibility of the small perturbation theory been verified by the results of numerical simulation and actual flight test.⑹The LFT modeling methods and available software packages been introduced, easy robustness analysis method based on structured singular value been proposed.Four aspects include theory, algorithm, modeling and engineering practice was studied around robustness of fly control law in this paper. Some methods and ideas of this paper can be applied to guide related control law design and robustness analysis of control law that designed. After appropriate expand, the results been studied in this paper can also be applied to full flight envelope stability validation of aircraft and robustness analysis of other control systems.