Integrated guidance and attitude control for pinpoint lunar guidance using Higher Order Sliding Modes

A novel non-linear guidance and attitude control scheme for pinpoint lunar landing is presented. The development of this algorithm is motivated by the desire to increase landing accuracy due to more stringent landing requirements in future lunar mission architectures and by the interest to integrate the attitude control and landing guidance into the same algorithm. Based on Higher Order Sliding Mode control theory, the proposed Multiple Sliding Surface Guidance and Control (MSSGC) algorithm has been designed to take advantage of the ability of the system to converge to the sliding surface in a finite time. The proposed MSSGC does not require the generation of a trajectory off-line and therefore it is very flexible without the need of off-line trajectory generation. The proposed guidance law is proven globally stable using a Lyapunov-based approach. Results from a set of parametric studies demonstrate that the MSSGC law not only drives the spacecraft to the desired position with zero velocity, but also with the desired attitude and angular rates.