月球着陆舱在制动减速段的控制研究

Controlling Lunar Lander during Powered Descension Phase

分析了月球着陆舱在制动减速段对于控制的要求。以燃耗次优为出发点,求解得到无需进行迭代计算的期望姿态角计算公式,推导出仅与着陆舱的状态变量和终端约束相关的显式制导方案。基于滑模变结构控制方法,根据实际姿态角和期望姿态角的偏差,采用指数趋近律和边界层削抖的方法,设计了姿态跟踪系统,给出了姿控发动机的控制方案。仿真结果表明,该控制系统能够实现制动减速段的飞行目标,着陆舱经过514 s飞行后,在距月面2 km处将速度减为零,将姿态调整到垂直向下,较好地完成了飞行任务。

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.