Analysis of RLV’s Coupling Characteristic and Control Strategy Design

Reusable launch vehicle (RLV) in the reentry process exhibit fast time-variation, strongly nonlinear and coupling characteristics, they all increase the complexity of attitude control system. After a vehicle’s mathematical model is built for the analysis of RLV movement and attitude control system design, then some operating points are selected from the trajectory and linearized. Several common coupling mechanisms are described, including the inertial coupling, the motion coupling, the Dutch coupling and the control coupling. Calculation results of rapid roll stability boundary are given, and a criterion of the Dutch-roll motion stabilization is proposed. Based on the analysis of the coupling characteristics, a RLV longitudinal and lateral/directional motion control strategy is designed: elevators are used to trim and control on the longitudinal channel; body flaps and RCS are used to hybrid control on the lateral/direction channel at low dynamic pressure and at high dynamic pressure body flaps can work alone. Finally, the 6 DOF simulation results prove the validity of the control strategy.