A RLV nonlinear optimal compound controller design

The reusable launch vehicle (RLV) has strongly nonlinear, fast time-varying characters and multiple control modes, which challenge attitude control in task-adaptability greatly. A nonlinear RCS/aerosurfaces compound controller control scheme was presented. First a RLV model equipped with reaction control system (RCS) and aerosurfaces is developed. Then fast and slow loops control system is designed based on time-scale separate theory. The optimal control law was implemented to generate optimal control moments. The control allocation maps the control moment commands into thrusters and aerodynamic effectors´ commands. The daisy-chain combination method is applied to the control allocation to deal with the harmonization problem of the RCS and aerosufaces. The Results show the compound control scheme meets the attitude tracking performance requirements. Simulation demonstrates that the nonlinear RCS/aerosurfaces compound controller saves RCS fuel effectively and achieves coordinated control between RCS and aerosurfaces. The control scheme can also be used in other reentry vehicles or aerospace planes.