Research On Attitude Control And Control Allocation For Hypersonic Vehicle

Due to the advantages of repeatdly used,wide flight range,orbit maneuver,designated area returning,therefore,the RLV has become the focus of research and development in many countries.The development of RLV is a complicated systematic project,which involving aerodynamic design,propulsion system design,thermal protection system,flight control system design,especially the attitude control and control allocation problem of the attitude adjustment and reentry of the RLV is one of the most challenging topics in flight control system of the RLV research and development process.Thus the attitude control and control allocation problem of the attitude adjustment and reentry of the RLV are researched in this paper.Firstlly,the mathematical model of the RLV attitude control is setablished.Based on the nonlinear dynamic inversion theory,dividing the RLV flight control system into internal and external loop,the stability of internal and external closed-loop dynamic inversion system is proved strictly with Lyapunov theory.To deal with uncertainty of RLV system model,a attitude cnotrol laws with double sliding mode variable structure based on sliding mode control theory is designed and the stability of closed-loop control system is analyzed.The simulation with Matlab shows that the double sliding mode variable structure control strategy can reduce the control system performance requirements of the RLV nonlinear system model,the attitude control effect is good,but there is a faint chattering phenomenon.Secondly,aiming at the chattering problem of double sliding mode variable structure control strategy,the RLV system model is strict linearization with nonlinear dynamic inverse theory,then the RLV attitude control laws is designed based on backstepping control theory.The attitude control based on neural network adaptive online function approximation is proposed to solve the "differential explosion" problem of the backstepping control system,and the stability of closed-loop control system is proved.The Matlab simulation result shows that the proposed control strategy can reduce as much as 50% of the response time,the effect of attitude control is remarkable.Finally,aiming at the reentry attitude control and control allocation of RLV,the mixed integer linear programming algorithm is proposed.This algorithm regards the RCS and aero suifaces as a whole,avoiding separately design control strategy.The Matlab simulation results show that the control allocation algorithm based on mixed integer linear programmingalgorithm can solve the control allocation problem with 16 actuators,it can maximize the use of pneumatic rudder deflection generated control torque,and save the fuel of RCS system.