Reusable launch vehicle control using linear-adaptive and subspace-stabilization techniques

New robust Right control laws are developed for a reusable launch vehicle. The wide range of Right conditions, and the impossibility to obtain wind-tu nnel data for most of the Right domain, requires using a robust control tec hnique. The use of linear-adaptive control techniques to design the traject ory autopilot and to solve the inversion problem is proposed. Subspace-stab ilization techniques are used to design the inner loop of control, which co ntrols the vehicle attitude, The control is structured in two layers, The o uter layer plays the role of an automatic pilot offering two operational mo des: a trajectory mode and an attitude mode. In the trajectory mode the Rig ht path and ground track are controlled, and in the attitude mode the autop ilot controls attitude angles. The commands generated by the automatic pilo t are inverted, by the use of a new and rather novel algorithm, to determin e the required pitching, Polling, and yawing rate commands, which are then tracked by the inner loop of control. The inversion implements either bank- to-turn or skid-to-turn steering. The linear-adaptive methodology circumven ts the use of difficult nonlinear control techniques and attendant analysis uncertainties through the use of linear disturbance accommodation observer s to estimate and cancel the combined effects of nonlinear and/or uncertain terms. Subspace-stabilization techniques are used to steer the, system err or state to a certain subspace S representing the described or specified se rvotracking error behavior, while controlling the motion on the subspace S to the origin in error space. Some numerical simulation results are present ed to demonstrate that the closed-loop response, with the proposed flight-c ontrol law, accurately tracks the prescribed flight and ground track trajec tories.