Controlling lunar lander during powered descension phase

Section 1 in the full paper gives Fig. 1 showing the schematic of the control system of the lunar lander. Section 2 presents its guidance scheme. The two subsections are: the simplified model of the lunar lander (Subsection 2.1) and the design of explicit guidance law with fuel consumption sub-optimality as the first consideration. In subsection 2.2, we solve the equations for calculating the anticipated attitude angles of the lunar lander with no iterations necessary. Section 3 explains the lunar lander's attitude tracking system. Its four subsections are: the attitude model of the lunar lander (subsection 3.1), the selection of sliding mode surfaces (subsection 3.2), the design of variable structure control law (subsection 3.3) and the ignition logic of attitude-control engine (subsection 3.4). In subsection 3.3, on the basis of differences respectively between the actual attitude angles of the lunar lander and its anticipated ones, we design its attitude tracking system using the exponent reaching law and the flutter reduction around boundary layers. Section 4 gives the computer simulation of the flight of the lunar lander during its powered descension phase. The simulation results, shown in Figs.2 through 7, indicate preliminarily that the control system designed by us can reduce to zero the velocity of the lunar lander when it is 2 km away from the lunar surface after flying 514 s.