Abstract: During the lunar orbit flight phase of the Chang′e-6 lander and ascender module (LAM), the 10N thruster (could be used in a force-couple method) on the ascender and the 150N thruster on the lander are implemented for the attitude control. However, there exists some fault cases when one 10N thruster failed to fire and the other pair one could work well, the propulsion system could generate opposite control torque due to the installation of thrusters and the attitude could be instable accordingly. To ensure the attitude stability in the 10N thruster fault case, a dual-loop fault tolerant attitude control is proposed with a 10N thruster in the inner loop and a 150N thruster in the outer loop. Numerical simulations illustrate that the LAM attitude in the lunar orbit could still meet the requirements even in the case of the 10N thruster fault. Therefore, the proposed dual-loop attitude control, which implements coupled attitude control thrusters and redundant thrusters, could effectively manage the coupled thruster fault and ensure the stabitlity.

Key words: Chang′e-6, lunar orbit, thruster, fault tolerant, attitude control, phase plane