Robust guidance law for drag tracking in mars atmospheric entry flight

Abstract

A robust entry guidance law is designed for drag tracking in Mars entry atmospheric flight for low-lifting lander with maximum lift-to-drag ratio of only 0.18. In the flight process the bank angle is the only control variable to be modulated to eliminate the tracking error when considering the initial derivation and parameter uncertainties. Firstly the tough problem of the guidance law design is analyzed which the input coefficient of the drag dynamics equations is uncertain due to kinds of parameter uncertainties. In this study, we divided input coefficient on both sides of the drag dynamics. Then the robust control applied to robot manipulators can be adopted for drag tracking in the entire Mars entry atmospheric flight. And we can guarantee uniform ultimate bounded stability of uncertain systems. Finally, Monte-Carlo simulation result demonstrates robust method leads to the landing precision within 15km of a specified parachute deployment piont while subject to significant parameters uncertainties.