System Identification of a Sub-Orbital Re-entry Experimental Vehicle

This paper deals with the identification of the aerodynamic model of the Unmanned Space Vehicle realized at the Italian Aerospace Research Center as an experimental platform for the development and demonstration of enabling technologies for aerospace vehicles. System identification aims at upgrading the aerodynamic data-base of the USV, developed through wind tunnel testing of sub-scale models and CFD, for the purpose of flight control system design in the extended flight envelope of the vehicle. Estimation of the parameters of a suitably structured aerodynamic model of the unpow-ered and reusable vehicle is carried out as a nonlinear filtering problem, in the framework of a multi-step approach where the aerodynamic coefficients are identified first and, in a following phase, the unknown parameters are adjusted. The Unscented Kalman Filter is used as a recursive parameter estimation algorithm. As the first mission of the USV took place recently, the methodology is applied to data generated by a realistic simulation model of the vehicle and its sensor suite, to assess the filtering performance of the algorithms in state and parameter estimation.