Guidance Law Design Of Terminal Area Energy Management For Reusable Launch Vehicle

Terminal Area Energy Management (TAEM) is a critical flight phase of the reentry returnprocess for Reusable Launch Vehicle (RLV), its main purpose is to control the aircraft reach to theauto landing interface smoothly. In order to meet different initial energy, trajectory design,longitudinal/lateral integrated guided and multi-constrained guided are studied.Through the establishment of three-DOF-degrees model, the object characteristic of the sampleRLV is analyzed. And RLV has the characteristics of unpowered, little and multiple lift-drag ratio andthe aerodynamic characteristics seriously affected by rudder, so the designs of trajectory and guidancelaw need to consider constrained state and the impact of the rudder.To satisfy the constraints of dynamic pressure, overload and angle of attack,the energy corridor isdesigned by using the dynamic pressure profile approximation the constraints, and analysis of variousuncertainties on the impact of the energy corridor， and the pneumatic uncertainty have seriousimpact on the energy corridor. In order to adapt to different initial height and energy state, tracks isproposed through designing different shape of the dynamic pressure profile, and compose trajectorydatabase; the reference trajectory is chose by interpolation of height and the relationship of energy andrange-to-go.In order to successful return in any energy, the longitudinal/lateral integration-guidance schemeconsists of lateral adjustment to the distance and vertical tracking the energy corresponding to thedistance is proposed. When the energy overflow or moderate, Lateral adjustment to the distance,vertical tracking altitude profile, and to ensure the accuracy of the energy management, speedbrakes isused by velocity control in the subsonic section. In the case of energy shortage, vertical keep flying inangel of maximum lift-to-drag ratio, lateral minimize the range-to-go, for reaching airport as soon aspossible. For the problem of overload, dynamic pressure and angle of attack constraint, switchingcontrol circuit in accordance with the priority to make the system safety. To realize the tasked and safyflight, the guidance law of the control and constraints loop is designed.Finally, the guidance system is simulate and tested aiming at uncertainties of different TAEMinitial status, aerodynamic parameters, wind disturbance, the results show the guidance scheme iscorrect and effective, and the robustness perform well.