Guidance of aeroassisted vehicles by static and dynamic feedback

Static and dynamic feedback control strategies based on geometric control methods are designed for aeroassisted orbital transfer vehicles. The two control objectives are asymptotic meeting of terminal conditions so that exit from the atmosphere can occur, and asymptotic output tracking of reference signals. Assuming parabolic drag polar, dynamic feedback and input-output linearization techniques are employed to decomposed the original nonlinear system into a linear controllable subsystem of degree three and a nonlinear subsystem of degree one. The control law is then designed based on the linear subsystem while the effects of internal dynamics of the nonlinear subsystem are investigated. Relaxing the parabolic drag polar or if desirable introducing it as a control constrain, we propose a new model which has as control inputs the lift and drag coefficients. This model is shown to be equivalent to a linear controllable system through nonlinear state and feedback transformation with inputs decouple from the outputs. Linear systems analysis and design techniques are then available to our disposal. Numerical simulations were carried out for the exact linearized decoupled system.