Simple adaptive re-entry control with actuator assignment

Simple adaptive control can be applied to any non-linear system, provided it is almost strictly passive. A necessary condition in that case is that each control channel is single-input single-output. Re-entry vehicles, where reaction and aerodynamic control are combined, do not fulfill that condition. In particular, gliding vehicles at large angle of attack, where the vertical stabiliser and/or winglets are partially shielded by the fuselage, need yaw thrusters to support the weak rudder control. Instead of commanding the actuators directly, a required moment per axis should therefore be commanded, and the actual actuator allocation should be done outside the controller. Not only does this make the closed-loop system almost strictly passive, but also the controller design is simplified. The current paper addresses such a control-system design, and shows response results for both longitudinal and lateral control in several mission phases that require the use of thrusters, control surfaces, and a combination of both. With relatively low design effort, a smooth and quick response is obtained that can easily be extended to integrated attitude control along the complete re-entry trajectory.