Modelling, simulation and validation of different control strategies for a launch vehicle with a non negligible roll rate

This paper is mainly focused on a comparison between different autopilots for launch vehicles having a non negligible roll rate. After a brief introduction on the important of mathematical model' s selection, two main design models for a launch vehicles have been introduced. Each of them will be used by a dedicated control strategies. The first one is based on the nonlinear feedback linearization control and the second one on the robust eigenstructure assignment using multi-model approach. These techniques were selected since they allow to enable coupling effects due to the non negligible vehicle roll rate and also the nonlinear characteristics of the systems (variable mass, ... ). The performances of each different autopilot will be evaluated using a complex flight dynamic simulator, which was built at ESA in the frame of support activities for VEGA launch vehicle. This simulator is based on the multi-body dynamic simulation software DCAP (Dynamic and Control Analysis Package) and allows full three dimensional, trajectory simulation with the launch vehicle structural characteristics modelled with time varying properties during the flight evolution.