Nonlinear trajectory tracking guidance with application to a launch vehicle

This paper presents a methodology for nonlinear guidance law design for aerospace vehicles to track a prescribed nominal trajectory. The guidance law is based on a continuous-time predictive control concept and is applicable to vehicles with general nonlinear dynamics. The feedback guidance commands can be obtained reliably and efficiently by a convergent fixed-point algorithm. A launch vehicle trajectory-tracking problem is used to demonstrate the application. Asymptotic tracking convergence under the proposed method is studied analytically. The guidance law guarantees the satisfaction of the angle-of-attack constraint and a normal load constraint. Simulations are done to test the guidance law for a variety of trajectory dispersions, disturbances, and modeling uncertainties.