Research On Fault-tolerant Control Technology For Hypersonic Vehicles With Aerodynamic Surfaces And RCS

Hypersonic vehicle has become a hot research focus in the aerospace area for its huge military application and broad cival application prospects all over the world.However,the reentry flight environment is complex,and height and velocity change in a large scale,which inevitably weakens the performance of control system and leads to faults.Therefore,it is a challenging and meaningful research subject to design an effective reentry fault tolerant control(FTC)system,which can guarantee the safety of flight control system with faults.This paper addresses the FTC techniques for reentry attitude model of hypersonic vehicles in the presence of actuator failures,and mainly studies the compound FTC schemes for hypersonic vehicles with aerodynamic surfaces and reaction control system(RCS).Firstly,the research background and significance of hypersonic vehicle are introduced,and the knowledge about hypersonic vehicles is described.An overview of the current state of study and research about attitude control techniques and FTC techniques for reentry hypersonic vehicles subject to actuator failures is presented.Secondly,an adaptive sliding mode FTC scheme based on radial basis function neural network(RNFNN)is proposed to solve the problem of attitude tracking for the reentry attitude dynamics of hypersonic vehicles in the presence of unknown external disturbances,additive fault and partial loss of effectiveness fault.A RBFNN is firstly designed to approximate the unknown additive fault.Then,the adaptive method is applied to deal with the unknown partial loss of effectiveness fault.Under some reasonable assumptions,the two-loop sliding mode control(SMC)scheme is adopted,and the fault-tolerant controllers of the outer and inner loops are designed to guarantee attitude tracking even with the presence of two kinds of unknown faults and external disturbances.Based on the Lyapunov stability theorem,the adaptive laws are designed to update the parameters in the fault-tolerant controllers.Thirdly,according to the characteristics of reentry flight,the compound FTC strategy for hypersonic vehicles equipped with aerodynamic surfaces and RCS is studied.Firstly,the two-loop SMC structure is designed for the reentry attitude model with parameter uncertainties and external disturbances to derive the desired control torque,which guarantees asymptotic attitude tracking.Then,the daisy-chained allocation method is adopted to solve the problem of coordination between aerodynamic surfaces and RCS.Considering the existence of aerodynamic surfaces faults,a control allocator based on quadratic programming method is designed to map the desired torque commands into the primary actuator: aerodynamic surfaces.RCS is activated only when the desired control torque cannot be achieved using aerodynamic surfaces alone.Moreover,a control allocation(CA)algorithm,using linear programming and a pulse width pulse frequency(PWPF)modulator,is designed to handle the CA problem of multiple coupling RCS thrusters.Finally,the compound FTC scheme based on aerodynamic surfaces and RCS is further investigated.Here,the compound FTC framework of the above part is used,and on this basis,an innovative CA algorithm of RCS is proposed,using a fuzzy logic controller,a decision-making mechanism and an optimization objective.Compared with the RCS allocation method designed in the previous chapter and the existing representative CA method,simulation results show that the proposed RCS allocation algorithm not only has better allocation performance but also improves attitude tracking performance.Furthermore,the participation of RCS also brings discontinuous control torque and CA error,which influences the closed-loop stability.In order to prove closed-loop stability under these influence factors,the designed compound FTC scheme and CA algorithm are thoroughly analysed.And on this baisis,a rigorous proof of closed-loop stability is given.