Robust Tube Fault-Tolerant Control For Flexible Hypersonic Vehicle Based On Model Predictive Control

Hypersonic vehicle has the characteristics of fast flight speed and high penetration success rate,and has huge military value and potential economic value.In this thesis,the robust Tube fault-tolerant control method based on model predictive control is studied for flexible hypersonic vehicle with parameter uncertainty,actuator fault and input saturation.Firstly,the Tube model predictive control(Tube-MPC)fault-tolerant strategy based on notch filter is proposed.Considering the low degree flexible modes,the polytopic linear parameter varying(LPV)model of flexible hypersonic vehicle is established based on Jacobian linearization and tensor product transformation,and the parameter uncertainty and actuator fault are converted to additional lumped disturbance term.The Tube-MPC trajectory tracking controller is designed to steer the actual trajectory approach the nominal trajectory and the nominal trajectory approach the reference trajectory.The additional lumped disturbance term is suppressed by the robustness of system.Here,the flexible modes are stabilized by feedback control as part of system states.In order to weaken the effect of flexibility,a notch filter is designed to eliminate the frequency response peak of flexible modes,and the influence of the filter on the system is analyzed.Finally,the effectiveness of the designed controller is verified by simulation.Secondly,considering the input saturation,the Tube-MPC fault tolerant controller based on sum of squares(SOS-Tube-MPC)is designed.The feedback linearization model of flexible hypersonic vehicle is derived,and the parameter uncertainty and actuator fault are transformed into control matrix and additional disturbance term.The feedback linearization polytopic LPV faulty model is established.The real input saturation is transformed into virtual input saturation equivalently.The multivariate linear fitting is used to approximate the virtual input saturation into virtual statedependent input constraint in polynomial.SOS is introduced to relax the polynomial constraint into the convex matrix SOS condition via linear matrix inequality(LMI).Considering the existence of virtual state-dependent input constraint,based on TubeMPC,a weighted composite virtual fault-tolerant control law is formulated as the combination of unconstrained control and auxiliary control.The real control law is obtained by inversion.Finally,the performance of the controller is verified by simulation.Finally,a composite fault-tolerant control strategy is proposed by combining the active fault-tolerant control based on fault isolation with SOS-Tube-MPC.The extended state observer is designed based on altitude subsystem to achieve fast and accurate estimation of additional lumped disturbance term.The compensation control law is solved based on the estimation result.The fault diagnosis state observer is designed,and the output residual function is constructed to achieve fault diagnosis by threshold judgment.Based on the fault diagnosis result,the composite fault-tolerant control law is obtained through combining compensation control law with SOS-TubeMPC control law.Finally,the performance of the composite fault-tolerant controller is verified by simulation.