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Stair-climbing function of Micro Mobile Robot（ MMR） conflict with their portability. The Beijing Institute of Technology has developed a four-wheeled MMR which can climb stairs by flipping chassis. This robot weights 2. 5kg,so it is portable and can be deployed by throwing in short distance. In allusion to that robot,three concerns as well as assessments in dropping process have been put forward. The hyperelastic model of rubber and elastic-plastic model considering strain rate of metals were established,and a finite element model（ FEM） was established with ABAQUS furthermore. The FEM was tested on three typical working conditions of dropping horizontally,vertically and side-vertically by 1m height. Problems of the original structure were discussed and optimization measures were put forward,concerning tire,shell and motor shaft and so on.Simulation experiments have been done to confirm the validity of those measures. The results show that the dropping resistance is improved,and the optimized structure can sustain drops of 3 m.

To investigate atomic oxygen effects on tribological properties of Mo/MoS2-Pb-PbS film and further enlarge application range, atomic oxygen exposure tests were carried out for 5 h, 10 h, 15 h, and 20 h by the atomic oxygen simulator with atomic oxygen flux of 2.5 × 1015 atoms/cm2·s. The exposure time in test was equivalent to the atomic oxygen cumulative flux for 159.25 h, 318.5 h, 477.75 h, and 637 h at the height of 400 km in space. Then, the vacuum friction test of Mo/MoS2-Pb-PbS thin film was performed under the 6 N load and 100 r/min. By SEM, TEM, and XPS analysis of the surface of the film after atomic oxygen erosion, it was observed that atomic oxygen could cause serious oxidation on the surface of Mo/MoS2-Pb-PbS film, and the contents of MoS2, PbS, and Pb, which were lubricating components, were significantly reduced, and oxides were generated. From AES analysis and the variation in the main element content, Mo/MoS2-Pb-PbS thin film showed self-protection ability in an atomic oxygen environment. Hard oxide generated after atomic oxygen erosion such as MoO3 and Pb3O4 could cause the friction coefficient slight fluctuations, but the average friction coefficient was in a stable state. [ABSTRACT FROM AUTHOR]

To investigate ultraviolet (UV) radiation effects on tribological properties of Mo/MoS2-Pb-PbS film, ultraviolet (UV) radiation exposure tests were carried out for 20 h, 40 h, 60 h and 80 h by space UV radiation simulation device developed by our team, which can reach 3 UV radiation intensity. The exposure time in test was equivalent to the radiation of 100 h, 200 h, 300 h and 400 h in the space. Then, the vacuum friction test of Mo/MoS2-Pb-PbS thin film was performed under the 6 N load and 100 r/min, and friction test time of each sample was 20 min. By SEM, TEM, XPS the composition and morphology of Mo/MoS2-Pb-PbS film surface after UV radiation were analyzed. UV radiation could change the microstructure significantly and relative content of S element and MoS2 on the surface of the films decreased, and light mass loss of the films occurred. The tribological properties will also recover with the increase of sliding time, although the friction coefficient fluctuation of the film increased at the starting stage of the friction test. The damage of Mo/MoS2-Pb-PbS under UV irradiation was mainly caused by the volatilization of the enriched S element in the surface layer due to the high temperature heating of UV irradiation. [ABSTRACT FROM AUTHOR]