Research On Tool-Soil Interaction In The Superficial Lunal Regolith Sampling Process

In recent years, the moon exploration has become a hot spot in the astronautics field, one important task of which is the lunar regolith sampling. The character of lunar regolith is greatly different from that of earth soil for the moon special environment, so the interaction between sampling institution and lunar regolith is very complex, and after coupling with the sampling manipulator multi-body dynamics characteristics, brings great trouble to the control system design. This paper is focus on the analysis of soil-tool interaction coupling in the shallow lunar regolith sampling process.The lunar regolith is modeled based on the discrete element method first, and the contact mechanics model of lunar regolith particle elements is given, and the calculation method of the normal and tangential contact force is illustrated in detail, then the particles movement after being pressed is solved using dynamic relaxation method. The physical and mechanical properties of lunar regolith are summarized, and a suggestion for selecting the lunar regolith macro and mesoscopic parameters on computer modeling is given.The discrete element software is applied for the dynamic simulation of the lunar regolith sampling process. The accuracy of the model is proved through the analysis of the lunar regolith dynamic slip process and the velocity and stress distribution at different time. Because the mutation of the bucket force at the sampling initial moment has a great influence on the system vibration, the shovel dug initial stress state under different shovel dug angles are simulated, and the lunar regolith deformation and stress distribution are observed, and the results show that the bucket force at initial time increases with the shovel dug angle, nearly linearly.The dynamic model of the lunar rover and sampling manipulator is established then. Load the bucket force and torque spectrum to the sampling manipulator end, meanwhile, apply the operation space control on the manipulator with a changing end load, and make the manipulator move based on the settled trajectory, to complete the soil-tool interaction coupling analysis in the superficial lunar regolith sampling process. The simulation results show that the control method can achieve high precision trajectory tracking of the manipulator end, and make the control torque in an ideal range, so the hybrid force/position control of the sampling institution can be achieved in the lunar regolith sampling process.In this paper, the shallow lunar regolith sampling process is dynamic simulated and the soil-tool interaction coupling analysis is performed. The results can provide theoretical reference to the future sampling method design and institution optimization design, and is of certain value for engineering application.