Hybrid Reentry Guidance Based on the Online Trajectory Planning

A hybrid reentry guidance algorithm is developed for a reentry vehicle.The online piecewise trajectory planning based on waypoints and trajectory tracking guidance algorithm are incorporated.The dimensionless kinematic equations of the reentry vehicle and the longitude-latitude expressions are established in guidance coordinate frame(GCF).The reentry constraints are described and incorporated in the proposed guidance algorithm.The way points based on the initial reference trajectory are designed to piecewise implement trajectory planning.The linear quadratic regulator(LQR) controller is designed to implement longitudinal guidance,and the lateral error boundary is given to determine the sign of the bank angle.Simulation and experimental results indicate that the average calculating time of each trajectory planning is less than 0.2 seconds and the guidance accuracy requirements are satisfied as well.