Passive Fault Tolerant Control For Hypersonic Vehicle Based On Model Predictive Control

Hypersonic vehicle has fast flight speed and strong penetration capability,and have broad application prospects in civil and military fields.In this paper,considering the parameter uncertainty,input saturation and actuator fault,the passive fault-tolerant con-trol strategy for the hypersonic vehicle in the cruise phase is studied.The main work is as follows:Firstly,for the longitudinal model of the hypersonic vehicle with actuator loss of effectiveness fault,random drift fault and lock-in-place fault,the linear time-invariant(LTI)model with polytopic additional disturbance term is established by feedback lin-earization and equivalent transformation of faults.The input constraints in the nonlinear system are transformed into the virtual control input saturation functions,which is state dependent.The linear regression based on least squares is adopted to approximate non-linear functions to polynomials and the sum of squares(SOS)technique is used to solve constraints.The norm-bounding theorem is used to ensure that the state of the dis-turbance system is in the same invariant set as the state of the nominal system.The fault-tolerant controller based on robust model predictive control(RMPC)and linear matrix inequality(LMI)is designed to realize the fault-tolerant control of hypersonic vehicle.Secondly,on the basis of the above,the parameter uncertainties of hypersonic ve-hicle are taken into account,and a polytopic linear parameter variation(LPV)model is established.Some of the uncertainties are reflected in the affine form of the input matrix,and the other part is transformed into additional poly topic uncertainties.Then,the loss of effectiveness fault,random drift fault and lock-in-place fault of the elevator are considered respectively,and the faults are transformed into disturbance terms,and together with the additional uncertainties,constitutes a lumped additional disturbance term.Based on SOS technique to deal with input constraints and norm-bounding the-orem to suppress faults,a SOS-RMPC fault-tolerant controller is designed to achieve stable tracking control of hypersonic vehicle.Finally,based on Jacobi linearization and tensor product transformation,a poly-topic LPV model of hypersonic vehicle is established.The three kinds of faults oc-curring on the elevator are transformed into bounded additional disturbances and an idmRPI-based weighted Tube-RMPC strategy is proposed.In this section,the concept of incomplete disturbance minimum robust positive invariant(idmRPI)set is proposed innovatively.Based on this invariant set,a weighted parameter is designed to adjust the control performance and robustness of traditional Tube-RMPC.In addition,the in-fluence mechanism of the weighted parameter on invariant sets and nominal control input constraints is analyzed in detail.By selecting appropriate weighted parameter,the control performance is improved,which avoids the disadvantage of overemphasizing robustness and ignoring control performance in traditional methods.A state observer is designed to estimate the unmeasurable state,which constitutes the output feedback control strategy.At last,the fault-tolerant control of the hypersonic vehicle is realized,and the purpose of improving the control performance is also achieved.