LPV Modeling And Control Of Near Spacecraft

The dynamic characteristics of the Near Spacecraft will vary considerably overthe flight envelop due to their extremely wide range of operation conditions and rapidchange of mass distributions. Furthermore, because of airframe-integrated scramjetutilized and the flight conditions of high altitudes and Mach numbers, manyaerodynamic and propulsion characteristics still remain uncertain and are hard topredict. As a result, the near spacecraft model is uncertain, multivariable, unstable,and possesses significant input-output cross-coupling. Therefore, it is essential tomodel and design flight controllers for near spacecrafts.In order to grasp the near spacecraft models complex dynamic characteristics, thedifferential equations of the near spacecraft rigid modes are established,based onLagrange equations;The flight trim points in the longitudinal motion modes underdifferent flight velocities and altitudes are computed, ultilize the aerodynamiccoefficients of the opened aircraft winged-cone, then the aircraft LPV model is set up.Furthermore, it is possible to provide appropriate objects to reduce the model anddesign flight control systems for near spacecraft.When pursuing an LPV formulation, one ends up with models of relatively largedimension. Accordingly, finding control syntheses usually requires substantialcomputation. For this reason, a LPV model reduction theory is proposed based onbalanced truncation method. First, the concepts of well-posedness and stability in anlinear fractional transformation framework are brought, the notion of balancedrealizations is defined utilizing the theory of generalized gramians; Then the paperprovides a generalization of the balanced truncation procedure for the LPV modelreduction; Finally, the proposed method is applied to reduce the near spacecraft LPVmodel.Considering the intense varies of the aero-thermal and aerodynamiccharacteristics, as well as numerous uncertainty and external interference,the the gainscheduled H_∞controller is designed, ensure good dynamic characteristics throughoutthe flight envelope, realizating the disturbance attenuation and system robust stability,as well as controller real-time dynamic adjustment.The conclusion and perspective are given in the end of the paper.