Rapid Algorithm for Generating Entry Landing Footprints Satisfying the No-Fly Zone Constraint

An online estimation algorithm of landing footprints based on the drag acceleration-energy profile is proposed for an entry hypersonic vehicle. Firstly, based on the Evolved Acceleration Guidance Logic for Entry (EAGLE), drag acceleration-energy profiles are designed. To track the drag acceleration-energy profile obtained by the interpolation, a drag acceleration tracking law is designed. Secondly, based on the constraint model of the no-fly zone, flying around strategies are proposed for different conditions, and a reachable area algorithm is designed for no-fly zones. Additionally, by interpolating the minimum and maximum drag acceleration profiles, the terminal heading angle constraint is designed to realize the accurate calculation of the minimum and maximum downrange ranges by adjusting the sign of the bank angle. In this way, the distribution of landing footprints is more reasonable, and the boundary of a reachable area is more accurate. The simulation results under typical conditions indicate that the proposed method can calculate landing footprints for different situations rapidly and with the good adaptability.

A New Evolved Acceleration Reentry Guidance for Reusable Launch Vehicles

in order to solve the poor adaptability problem with the traditional reentry guidance, A new evolved Acceleration Guidance Logic for Entry (EAGLE) is studied for the Reusable Launch Vehicle (RLV) here. According to the guidance, the reference drag acceleration profile is updated every period based on the predictive range-to-go. In the lateral profile, basing on the generated reference drag profile, two reversal times are got successively through numerical predictive method. The technique of feedback linearization is used to track the reference drag acceleration profile. The algorithms of updating the reference drag profile and searching reversal times are both the method of golden-section search, so the EAGLE method can be performed onboard. The simulation results based on different reentry conditions show that the approach has good robustness and real-time ability.

A New Angular Acceleration Guidance Law with Estimation Approach Based on Sliding Mode Observer against High Maneuvering Target

A new type of guidance law is developed for intercepting high maneuvering target. The law takes angular acceleration of line-of-sight as a primary input in place of the acceleration of target. As the significant required input quantity of the angular acceleration guidance (AAG), the angular acceleration of line-of-sight is estimated by a developed estimation approach based on sliding mode observer (SMO). Simulation results demonstrates advantages of this AAG guidance with the estimation approach based on SMO by comparing with the conventional guidance techniques and extended Kalman filter.