Modeling and analysis of length variable loading wire ropes in lunar soil drilling

In deep lunar soil sampling, the drilling mechanism is driven by the loading wire rope through a driving mechanism. This paper is aimed at establishing an accurate dynamic model of the removable loading wire rope and analyzing its influence on the drilling process. In the process of drilling, there exists material transportation at the boundaries, so the length and mass of the upper and lower wire ropes are time-varying. Using absolute nodal coordinate formulation (ANCF), the model of variable-length flexible cable element which considers the preload is derived by combining Euler and Lagrange nodes. Compared to traditional ANCF cable element, a material transportation item which is associated with the moving velocity is added up to the new element. The variable-length and traditional cable are respectively used to establish the boundary and internal elements. The simulation results prove that the movement and vibration of the variable-length wire ropes can be well simulated by the length variable flexible cable model. Then the influences of preload and impact frequency are studied. The greater the preload, the larger the natural frequency and smaller the vibration amplitude will be. When the impact frequency approaches the natural frequency, the resonance occurs, and the vibration amplitude increases.