ESA GNC Conference Papers Repository
Launchers Analytical Loop Shaping Design and Validation
Methods of launcher control are as diversified as control. Among the popular method, already implemented and flight proven by Astrium Space Transportation can be found Hinfinity control, LQG methods on Ariane 5, analytical controller providing fixed minimum worst case margins of the rigid body mode on ballistic missile. In order to get fast generation of control laws with various launchers configuration, AST has developped a loop shaping analytical method enabling comparison of stable vs unstable controller, possible implementation of transverse feedback in Terrestrial Reference Frame (TRF) or Launcher Reference Frame (LRF), providing directly worst cases gain and phase margins, controlling bending modes either in gain or phase. The developped tool is currently used to generate control law for a small launcher. It provides comparable results to optimal control methods such as Hinfinity, mu-synthesis and is much faster to implement. The paper provides an insight into the architecture of the control law. It recalls the necessary steps to elaborate it and presents the principles of the loop shaping method. Finaly, the efficiency of the method is demonstrated on two current AST problems where exist simultaneously strong requirements on maximum aerodynamic loads, large uncertainties, highly excitable bending modes.