月球重力转弯软着陆的模糊变结构控制

Fuzzy variable structure control for lunar gravity-turn landing

针对月球软着陆的最终段,提出了以重力转弯方式进行软着陆的模糊变结构制导律.首先设计了次优滑动面,然后引入模糊控制器,使滑动变量逐渐收敛到0,实现安全着陆.考虑了发动机推力偏差、着陆器初始质量估计偏差、月球引力加速度偏差、初始条件干扰、敏感器测量误差及姿态跟踪误差.并用Monte Carlo技术验证了所设计的模糊变结构制导律具有很强的鲁棒性,能够克服各种随机偏差及干扰的影响.因此,所设计的软着陆制导律是可行的,并且只须以斜向距离和斜向速度作为输入,工程实现简单.

Based on fuzzy variable structure control, a new guidance law of gravity-turn landing has been developed for the terminal descent phase of lunar soft landing. The sub-optimal sliding surface and fuzzy controller were designed to drive sliding variable converging to zero that would make a soft landing on the lunar surface safely. The bias of the descent engine＇s thrust, the estimation of the lander＇s initial mass and the lunar gravitational acceleration, the disturbances of initial conditions, the measurement error of sensors and attitude tracking error were considered. The Monte Carlo simulation has demonstrated that the guidance law is robust to all bias and disturbances. Therefore, the guidance law designed is feasible. It requires only slant range and slant range rate, and it is easy to implement in lunar soft landing mission.