Steady glide trajectory planning method for hypersonic reentry vehicle

The concept of steady glide trajectory with minimum integration of the change rate of longitudinal acceleration was proposed for the equilibrium glide problem with given angle of attack and bank angle profiles,and the planning method of the steady glide trajectory was described. First,the dynamic differential equation in the altitude direction was solved by regular perturbation,and steady glide analytical solutions with high precision,including height,flight path angle and longitudinal acceleration,were obtained. Then the dynamic behaviors of the steady glide trajectory were analyzed,the natural stability and low damping of the trajectory were found,and the expressions of natural frequency and damping were obtained. The results show that the natural frequency is only a function of velocity,while the damping depends on velocity and longitudinal lift-drag ratio. Finally,the pure differential feedback of height deviation is found to be the best scheme for restraining the oscillations of the steady glide trajectory among three feedback schemes,which are pure differential feedback,pure proportional feedback and proportion-differential feedback. The simulation results show that the control of the pure differential feedback scheme is steady,the trajectory oscillation decay fast,and the robustness of the scheme is excellent.