Abstract: In order to obtain landing stability criterion of legged-type spacecraft lander and methods of improving its landing stability, the structural principle of legged-type lander is given. The flow chart of landing stability analysis, which is according to the structural characteristics of legged-type lander and the study of stability of the landing processing based on zero moment point (ZMP), is proposed to provide useful reference in stability study of legged-type spacecraft lander. In order to validate the corrective- ness of the stability study of legged-type spacecraft lander based on the ZMP, a four-leg truss-type lunar lander prototype developed by Harbin Institute of Technology is taken as an example to combine with the proposed method of the stability study of legged-type spacecraft lander, the relation diagram of support polygon and ZMP is given. The formulas of the support polygon and ZMP of the prototype in the landing process are obtained and finally the stability determination method of the legged-type spacecraft lander is given by judging whether ZMP lies inside of support polygon or not.

Key words: Criterion, Lander, Stability, Support polygon, Zero moment point