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Analysis of drill stem structural and kinematic parameters of lunar drilling sampling mechanism

WANG Lili;LIU Zhiquan;WU Weiren;ZHANG Zhijing;Mechanical and Vehicular Engineering College,Beijing Institute of Technology;China Academy of Space Technology;Lunar Exploration and Aerospace Engineering Center;  
In respect of the sampling process of the hollow-external-screw drill stem for automatic drilling sampling mechanism,the mathematical models between the cohesive force,friction coefficient of lunar-soil and the lunar-soil depth are built separately;the relationships between drill stem kinematic parameters(drill stem drilling speed and rotary speed)and the structural parameters(drill stem spiral angle,outside diameter,groove width ratio and spiral grooved depth in the drilling process)are also established.These models take into account not only the characteristics of lunar-soil physical and mechanical parameters changing with drilling depth and drill stem drilling convected velocity,but also the shear resistance among lunar-soil infinitesimals.Such approach subjects the drill stem's parameters to the job requirement of lunar drilling sampling.The effectiveness of the model is validated and the analysis of the influence of the drill stem structural parameters on its kinematic parameters is conducted with the models.As a result,the influence law of the drill stem structure parameters on its kinematic parameters is revealed,and the best value range of drill stem structure parameters is obtained.Taking the minimum value of the ratio between the drill stem rotary speed and drilling speed as optimal object and the structural parameters as design variables,based on genetic algorithm,the structural parameters of drill stem are optimized.Before and after optimization,the ratio of drill stem rotary speed to drilling speed is reduced by 13.8%.The research results will reduce the energy consumption and improve the efficiency,which provide a theoretical basis for the design of automatic drilling sampling mechanism.
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