Low order LFT modelling and generation from the non-linear equations of motion for a fighter aircraft
Tóm tắt
The development of an LFT representation for the nonlinear HIRMplus research model is presented. The structured singular value /spl mu/ is applied on the so developed LFT in order to clear critical areas in the flight envelope. /spl mu/-analysis allows to determine the combination of uncertain parameters within their respective bounds, for which a performance criterion or stability margin is worst. For a sensible worst-case analysis, it is important that the uncertain parameters are directly related to the physical uncertain/varying parameters in the nonlinear model. First a symbolic nonlinear model of the HIRMplus is developed, which depends on the physical parameters of interest in a rational way. Then the model is linearised symbolically. A low order LFT model is generated and compared with one obtained using an affine modelling approach. Although both model representations are aimed to cover the same flight conditions, the affine model is a function of a large number of artificial parameters. Both models are compared regarding their ease of generation, conservatism, accuracy, and applicability.
Từ khóa
#Nonlinear equations #Robustness #Aerodynamics #Uncertainty #Military aircraft #Stability criteria #Aerospace control #Feedback #US Government #ProtectionTài liệu tham khảo
cook, 1997, Flight Dynamics Principles
10.1016/S0005-1098(97)00049-6
lambrechts, 1993, Parametric Uncertainty Modeling using LFTs, Proceedings of the American Control Conference, 267
1997, Robust Flight Control Design Challenge Problem Formulation and Manual: the High Incidence Research Model (HIRM), Garteur FM-AG08
10.2514/2.4708
magni, 2001, Linear Fractional Representation: a Toolbox for Use with Matlab, GARTEUR FM-AG11/TP-119–11
bates, 2000, Clearance of the HIRMplus RIDE Flight Control Law: A µ-analysis approach, GARTEUR FM-AG11/TP-119–11
andrea, 1997, Kalman Decomposition of Linear Fractional Transformation Representations and Minimality, Proceedings of American Control Conference, 10.1109/ACC.1997.609484