88 / 2017-04-28 21:23:22

An Integrated Trajectory Guidance and Attitude Control Law with Enhanced Anti-Disturbance Capability for Mars Pinpoint Landing

Mars pinpoint landing; powered descent; trajectory guidance; attitude control; disturbance observer based control

Guidance and control accuracy could be essentially improved by using the unified algorithm for a Mars lander compared with the traditional guidance and control algorithm and a novel integrated trajectory guidance and attitude control law is presented in this paper. In a Mars mission there will be various disturbances such as the unpredictable gust during the powered descent stage and the actual trajectory and attitude of a Mars lander will be directly affected seriously. In the proposed algorithm the effect of major disturbance could be estimated through a disturbance observer and then it will be incorporated in the feed-forward compensation. Afterwards, the residual other disturbances could be attenuated by the multiple sliding surfaces techniques. Such a composite hierarchical framework is composed of the feedforward compensation and the feedback control. This strategy does not require a pre-computed reference trajectory and it could be applied to reduce the conservatism of the system. Its global stability is verified using Lyapunov-based approach. Simulation results show that this algorithm could guide and control the Mars lander safely and accurately according to the Mars mission, which has enhanced anti-disturbance capability comparing with traditional guidance and control law in the presence of disturbances.