Ascent Trajectory Design And Optimization For Hypersonic Vehicle Under Control Constraints

Hypersonic vehicle which is a brand-new vehicle with a wide application prospect has achieved a rapid progress in recent years.New requirements are imposed on the trajectory design,optimization and guidance system due to these characteristics concerning high-speed,long-voyage and strong-maneuvering.Based on this,this paper focuses on the design,optimization and control of the ascent trajectory of the hypersonic vehicle under different control constraints.Firstly,the wave riding configuration of the hypersonic vehicle is selected based on the task requirements,and the parametric modeling method is employed to build a mathematical model of the vehicle.The aerodynamic force and thrust are approximately obtained using the engineering estimation method so as to construct a complete model of hypersonic vehicle and then the dynamic characteristics of the aircraft are analyzed.Furthermore,the ascent trajectory in the whole flight envelope is designed under the condition of constant dynamic pressure and constant Mach number.Then,an approved trajectory inverse algorithm based on the Newton Raphson method is presented for the hypersonic vehicle to compute the control input in relation to a desired trajectory.Furthermore,the ascent trajectory with constant dynamic pressure is analyzed by applying the inverse simulation,and the feasible domain of the dynamic pressure is determined under the control input constraint as a result that the trajectory optimization constraints are obtained accordingly.After that,the Gauss Pseudo-spectral Method(GPM)and the Sequential Quadratic Programming(SQP)algorithm are applied to obtain the optimal ascent trajectory with constant dynamic pressure.The feasibility of the design process is verified by the comparison of the optimal trajectories and the design trajectories.Considering the dynamic pressure constraint,the initial point of the ascent trajectory is determined on the fixed terminal conditions,and the fuel optimal trajectory under the control constraint is eventually obtained by the use of GPM.Finally,the trajectory tracking controller is designed based on the Linear Quadratic Regulator(LQR)theory for the fuel-optimal trajectories.Furthermore,simulation results show that the designed controller can ensure that the hypersonic vehicle follows the fuel optimal ascent trajectories and constant dynamic trajectories effectively in the presence of the initial value and aerodynamic parameter errors.