A gain scheduled H-infinity controller for a re-entry benchmark

In this paper we present the design process and results for a re-entry baseline controller used as a benchmarking reference within a European Space Agency (ESA) project on advanced gain-scheduling techniques. The controller is based on output gain-scheduling of a set of LTI H∞ controllers obtained using a decoupled motion approach. The rationale behind the selection of the design points, and the analyses and guidelines used in the design and tuning of the controllers to satisfy the desired global performance and robustness objectives are described in detail. The re-entry vehicle used is an enhanced version of the well-known NASA HL-20 based on a detailed NASA aerodynamic database and including nonlinear actuators, colored sensor models, realistic uncertainties and a control mix logic. The latter logic fully couples the longitudinal and lateral/directional motions while the noise and uncertainties used are key in making of this enhanced HL20 a realistic benchmark for reentry control design.