Dynamics And Stability Of Planet Module Landing Gear With Primary/Secondary Struts

Exploring celestial bodies and exploiting their resources by landing on them is a tide of new round international space exploration. In the second phase and third phase lunar exploration project"Chang'e Project"of our country, perambulating on the moon and coming back with the sample of moon will be actualized. Manned lunar and Mars exploration is also strategic target of space science and technology development. The soft landing of the module on celestial body surface is a crucial and basic event of exploration. Deployable struts landing gear is a widely used type of landing gear, which has good adaptability.From the current situation, although some results of research on the structure and buffer design have been got, the researches on the dynamics and stability of the landing gear during deploying and touchdown processes, which are the key issues of soft landing, are still deficient. This work was supported by the National Natural Science Foundation of China (Grant No.50775048) named"Aptitude design method of new buffer of celestial body explorer lander and touchdown stability analysis", this dissertation launches under this background. Researches on the dynamic characteristics and stability of the planet lander during the landing gear deploying and the lander touchdown processes are carried out, so that to provide theoretical basis and support for the development of our country's celestial body module landing gear.First, the application and development of the landing gear of planet lander are proposed. The modularization design of main structure, struts and buffers of the lander is discussed. The dynamic researches in the phases of launch, flying in the orbit, during landing and after landing of the lander are presented. The current planet landers are classified according to the leg structure of landing gear. The basic theoretics of dynamics and stability are summarized.Then, the dynamics and stability of the lander in landing gear during deploying and touchdown processes are researched on.Kinematics characters of two typical deployable landing gears are analyzed and compared. The dynamic model of landing gear in deploying process is built according to the theory of rigid-flexible coupling with clearance multibody system dynamics for the first time. The virtual prototype model of a lunar lander with four strut groups is built. The effects of the flexibility of primary strut, joint clearance, deploying driver force and the spin of mainbody on the dynamic character of landing gear during deploying are analyzed.With the overhanging beam model with mass at the end model of landing gear strut, on the assumption that the main body's state of motion is constant, the stability of vibration of primary strut undergoing deploying large overall motion is analyzed in the deploying plane. On the assumption of free system in space, the stability of the overall module system is researched. This modle and stability analysis method also can be used in other spacecraft with similar structure.The key issues of lander landing model are illuminated systematic. Then based on Lagrange equation of the first kind, the touchdown dynamic model of planet lander is built. The structure characters, description, logical basic assumptions and the implement on software of the main body, the landing gear and the planet surface environment are researched. A simple and pritical method for multilevel honeycomb buffer simulation is built. As an example, the simulation model of a lunar lander with four cantilever truss style landing gear is built. The influences on landing acceleration and motion state by the character of landing orientation, buffers in struts of landing gear and the landform of the moon are analyzed.The static stability criterion is established and used to compare the influences of structure parameters on static stability of the lander with three and four landing strut groups. To ZMP (Zero moment point) theory, the real time stability criterion of planet explore lander in touchdown process is established. The supplementary conditions on preventing the slippage and the slip-rotation are affiliated. The condition on rebound prevention is researched by spring damp model. The initial conditions on touchdown topple prevention is researched by extension inverted pendulum model and compared with the conditions which are gotten by using inverted pendulum model. The dynamic equation is established for simplified model. Then this equation is used to research the stability in the sense of stability theory. The structural framework of landing stability analysis is built.