ESA GNC Conference Papers Repository
Flight Control Strategies for Transonic Phase of High Lift Reentry Vehicles: Comparison and Flight Testing
The return to earth from the Moon or from the outer space consists of three phases: Entry, Terminal Area Energy Management (TAEM), and Approach and Landing. During the TAEM phase the vehicle decelerates from about Mach 2.0 to 0.2 flying through supersonic, transonic and subsonic aerodynamic regimes. The unsteady nature of the flown trajectory, the very wide flight envelope, the rapidly changing environmental conditions and the wide uncertainty ranges (mainly due to the difficulty of achieving accurate aerodynamic prediction for the transonic flight phase) affect the design process and make the vehicle control problem very challenging. The Italian Aerospace Research Center (CIRA) is conducting a national research program named USV (Unmanned Space Vehicle) with the objectives to develop, demonstrate and validate enabling technologies for future aerospace vehicles. Two flight tests called Drop Transonic Flight Tests (DTFT1 and DTFT2), have been successfully conducted on February 24, 2007 and on April 11, 2010, respectively. These tests had the main aim of investigating subsonic and transonic regimes using the CIRAs Flight Test Bed 1 (FTB-1), an unmanned and unpropelled vehicle, with a medium aerodynamic efficiency. This paper discusses the process of designing a control system that operates during the TAEM phase of an high lift re-entry vehicle, both evidencing the critical issues and proposing some effective solutions that have been adopted for the DTFT2 mission. A comparison among different control strategies (?-Control with Fuzzy Logic Gain-Scheduling, Direct Adaptive Model Following, Probabilistic Robust Control Synthesis) is reported with reference to the DTFT1 mission. Furthermore the application of the selected algorithm and the related DTFT2 mission flight test results are also discussed.