Robust Three Axes Autopilot for a Tactical Aerospace Vehicle

The nonlinearity and coupling of the aerospace vehicle dynamics can be linearized and decoupled by well known feedback linearization techniques. But, this technique fails to handle the uncertainties in the system due to aerodynamic coefficients. This problem becomes acute when an aerospace vehicle tries to attain high angles of attack during flight. Significant research works are devoted in accordance to this. In this paper, a new robust nonlinear controller structure using feedback linearization technique is presented. The design is carried out in two time scale separation. The fast dynamics (inner body rate loop) and slow dynamics (outer latax loop) are controlled separately by two nonlinear controllers. The performances of the design in terms of robustness, minor coupling between the longitudinal motion and lateral motion, stability and guaranteed tracking are shown in a very realistic 6-DOF simulation