Mechanical Property Analysis And Optimization Design Of The Hold-type Transport Mechanism Of Lunar Rover

The exploration of the unknown world is the motive power of human technologicaldevelopment. The deep space exploration is an important activity in the process ofexploring the unknown. As an optimal springboard and transfer base of human’sexploring the solar system and other planets, the moon becomes a first target of deepspace exploration. Lunar exploration rover (or Lunar rover vehicle) used to explore isan important means of lunar exploration, but it can not directly descend to the surfaceof the moon. Lunar rover vehicle must be equipped with a lander of buffer device andis transferred to the lunar surface with the dedicated special release device from thelander equipped with tanks after a safe soft landing of the lander. The special releasedevice is transfer mechanism, and directly determines the success of a lunarexploration project as a bridge between the lander and lunar surface.In order to complete the lunar exploration mission successfully, we must solvestructure of the transfer mechanism stiffness and strength, adaptability of the lunarsurface, as well as the stability and reliability in the process of the inspector transfer.In the launch and flight phases, the transfer mechanism which has sufficient stiffnessand strength to withstand emitted overload, and withstand complex impact load andstructural response when a soft landing of the lander need to be pressed against thelander; After landing, the transfer mechanism requires the ability to adapt to the landerattitude and working conditions of the lunar surface, and guarantees safe and reliabletransfer smoothly to the lunar surface and a smooth separation in possible extremeworking conditions.Therefore, to solve the major theoretical and technical problems, this thesis carriesout extensive literature research, uses the aerospace mechanics theory, numericalmethods of calculation and experimental analysis, and originally proposes a noveltransfer mechanism. Targeting to their lightest structural quality meeting its launch andworking environment, it carries out the structural optimization design of transfermechanism to ensure that the feasibility, reliability and stability in the process ofinspections release and transfer. Main research results obtained are as follows:(1) This thesis compares and studies a typical example of the transfer mechanismapplied abroad successfully and its configuration features and applicable conditions,draws an overview and summary of technical characteristics of the transfer mechanism on the principle prototype program, and proposes the hold-type transport mechanismprograms through combining with the second phase of China’s lunar explorationmission objectives and technical requirements and characteristics.(2) For the whole working process of the lunar transfer mechanism as well as thetypical limit conditions, the mechanical models of the various stages of the transferwork are built by use of the principle of kinematics and dynamics, the mechanicalloads of the various stages of transfer mechanism bearing members are calculated bythe application of classical mechanics method, and then the dynamics of the process ofthe transfer mechanism work are analyzed by using the multi-body dynamics software.The payload data of the respective bearing member of the transfer mechanism isdetermined through the comparison between theoretical calculations and simulationanalysis.(3) For the characteristics of heavy and poor environmental adaptability ofaerospace motor, this thesis proposes a special opening annular cross-sectionthin-walled torsion bar to replace the motor as the power source for the program ofhold-type transport mechanism. In order to obtain the performance data of openingannular cross-section thin-walled torsion bar, the torsion differential equations of theopening ring-shaped cross-section thin-walled torsion bar are established based on theSaint-Venant principle, small deformation theory and the outer contour of the sameassumptions, and the torsion properties of the opening ring-shaped cross-sectionthin-walled torsion bar and its stress-strain relationship are obtained by solvingconstrained torsion differential equations with the initial parameter method; Thenthrough theoretical calculations combined with numerical methods and experimentalresearch methods, the mechanical properties of the torsion bar are studies and thetorsion mechanical characteristics of the opening ring-shaped cross-section thin-walledtorsion bar are determined.(4) For the lightweight of space agency and environmental requirements, the swingarms of transfer mechanism are designed by using a carbon fiber composite material.For the special properties of carbon fiber composite materials, the stress-strainrelations of anisotropic carbon fiber composite materials are studied based on theclassical laminated plate theory and the anisotropic multi-layered carbon fibercomposite materials unit model is built by layered solid element model; Then theboundary constraint conditions of the transfer mechanism are defined according to theload conditions of the hold-type transport mechanism, a finite element model of the transfer mechanism of various typical conditions is established and the resonanceanalysis and mechanical check are conducted on the mechanical environment andtypical limit conditions in which the transfer mechanism is, and the study of themechanical properties of hold-type transport mechanism is completed.(5) For the larger span swing arm, the design of its cross-sectional dimension isoptimized by use of multi-objective particle swarm algorithm under the constraintconditions of structure quality and the design objective function of swing arm stiffness;For the lifting frame of the spatial structure, the topology optimization design of liftframe under multiple working conditions is conducted by using variable densitymethod under the constraint conditions of lifting frame’s size and the objectivefunction of structure compliance. Through the size optimization and topologyoptimization of the main components of transfer mechanism, the design of hold-typetransport mechanism is improved, and the structure stiffness, strength and reliability oftransfer mechanism are increased.(6) In order to verify the feasibility and rationality of the entire hold-type transportmechanism programs, the attitude simulation test platform under the limit conditionsof the transfer mechanism is designed based on a concentric three-bearing bodies, andthe feasibility and reliability of the transfer mechanism structure design is verifiedunder the related functional verification and environmental adaptability verification ofhold-type transport mechanism.