Design And Research Of Lunar Soil Drilling Load Mechanism

One of the main tasks of China’s Phase III Lunar Exploration Project is to acquire lunar soil sample more than two meters deep under lunar surface. For an essential part of drilling and sampling device, functioned as the drilling pressure and speed providing apparatus, excellent performance and structural reliability of load mechanism guarantees the reliability of drilling and sampling mission. Faced with the situation of technology blockage of foreign developed countries and relatively late developing on this area, few research and information is announced. The research of design and analysis of load mechanism is necessary for the purpose of analyzing performance and enhancing reliability. The results will provide technical support for drilling and sampling device of China’s Phase III Lunar Exploration Project.Based on the general requirements of drilling and sampling task, functional index is proposed and mission profile is analyzed. Margin model of load mechanism is set up. Margin design of load mechanism output unit is implemented under margin analysis of driving force. Reliability analysis model is set up in FMEA and FTA method respectively, illustrating the relationship between fault and whole reliability, getting the key structure of load mechanism qualitatively and quantitatively.Two structural schemes according to connection mode and guidance mode between drum and wire rope are proposed respectively. Mechanical mode is established in each scheme so as to analyze the interaction between structural parameters and load performance. Relevant model parameters are determined in certain scheme. AHP is used to establish an evaluation model for optimization of above four load mechanism driving unit interface schemes.The structure of load mechanism driving unit is designed. Mechanical model of shaft stress is set up and calculated as well as checked by FEM software. The key dimension of pulley is optimized through static and thermal simulation analysis. Parabola model of wire rope is set up. The relationship between pre-tightening force and performance of wire rope is analyzed according to static force, vibration and additional internal force, to determine the minimum initial pre-tightening force. Beam element model of thin-walled drum is set up, along with derivation of deformation formula of drum winded by wire rope windings and getting the drum deformation in two limited working positions through simulation analysis.Considering rigid-flexible characteristic of load mechanism, rigid dynamics and elastic dynamics model are set up first. Introducing flexible links such as clearance and damping, mathematical model of each component of load mechanism is set up by centralized parameter method to establish rigid-flexible dynamics model. Dynamic response of drilling system is analyzed by numerical simulation in the situation of drilling rig drill into lunar soil and lunar rock. Adams Cable module is introduced, to set up and simulate the sheave system in order to analyze the relationship between parameters of wire rope and dynamic response of system. By simulating and analyzing variable parameters, the relationship between the parameters of load mechanism and dynamic response of system is get and relevant parametric optimization objective is determined further.