Control of a Reusable Launch Vehicle

Abstract: Abstrakt: This report examines different control design methods, linear as well as nonlinear, for a suborbital reusable launch vehicle. An investigation of the natural vehicle behavior is made, after which a baseline linear controller is constructed to fulfill certain handling quality criteria. Thereafter the nonlinear cascade control methods block backstepping and nonlinear dynamic inversion via time scale separation are examined and used to construct two nonlinear controllers for the vehicle. Optimal controllers, in terms of three different criteria, are found using the genetic optimization algorithm differential evolution. The optimal controllers are compared, and it is found that nonlinear dynamic inversion via time scale separation performs better than block backstepping with respect to the cases investigated. The results suggest control design by global optimization is a viable and promising complement to classical methods.