| Regolith information,including its physical form,chemical composition,geological structure and surface heat flow,is important as it can improve people's understanding of planetary evolution and the origin of life.In the meanwhile,it is also necessary for future planetary exploration activities and resource utilization programs.Compared with nearsurface single-point exploration,acquiring the distribution characteristics of lunar subsurface information along the depth is of greater scientific importance.However,conventional continuous drilling method has a high mass power consumption,a complex system,and poor sensor carrying capabilities.Considering the working environment characteristics of lunar subsurface,an inchworm type excavation detection method is proposed.The inchworm type excavation robot(hereinafter referred to as the excavation robot)is attached to the surface equipment through the umbilical cable to achieve power and data transmission.The excavation robot is able to sneak to the lunar subsurface automatically,and carry out in-situ exploration by means of internal scientific instruIn order to achieve the objectives of automatic excavation of lunar soil profile and multiple parameters identification of lunar soil mechanical properities,following researches are conducted: Design of subsurface inchworm type excavation robot;Research on the mechanical model of lunar soil transport in the excavation;Excavation robot parameter optimization and experimental research of excavation process;Identification methods of mechanical parameters of in-situ lunar soil and its experimental research.Considering the mechanical properties of subsurface lunar soil,several detection methods are carried out and then compared for the large-depth penetration detection targets in the lunar subsurface.An inchworm type excavation detection method is proposed and its excavation and exploration capabilities are designed.In the meanwhile,the principle feasibility of the method is demonstrated by the analysis of the lunar soil transport theory.The design criteria of light-weight and low-power consumption are adopted to optimize the transmission layout of the excavation robot.Considering the poor fluidity and strong abrasive wear of lunar soil,the torsional design of the excavation robot in the lunar hole,the sealing design based on the effect of single-direction particle flow and the design of lunar soil transport channel with variable length are carried out.Furthermore,the control system is put forward,and the system integration design of the excavation robot is completed.Considering the low speed spiral transport caused by “low-power input limitation”,the additional extrusion stress between lunar soil particles is introduced to analyze the motion and the force of lunar soil during transport in the spiral groove,and establishe the mechanical model of lunar soil transport.Based on the basic assumption of the powder stress of Janssen,the stress model of lunar soil in the storage area is established,which provides a boundary condition for the excavation load model.Considering the soil transport effect of large section drilling bit,the conical spiral edge structure is proposed as the the soil transparent is robust.In addition,the lunar soil motion model during drilling process is established and thus the rationality of the structure is verified by simulation.The drilling cutting parameters of drilling bit are deduced,and the shear failure mode of in-situ lunar soil under cutting action is analyzed.Based on Mohr-Coulomb strengthen theory,the cutting load model is established.The model is verified by drilling cutting tests,which provides a theoretical basis for identifying mechanical parameters of high density lunar soil.An excavation load model is established and it is then verified by experiments,which provides a basis for parameter optimization and lunar soil mechanical parameters identification.Parameter optimization for storage area,boring bit,and soil transport spiral is carried out based on the mechanical modle of lunar soil transport.Aiming at establishing an equivalent flow model of lunar soil during drilling,a discrete element particle simulation model is established.This is followed by a series of researches including the simulation of lunar soil partile flow,the simulation of blocking effect of lunar soil flow in the storage area,and parameters optimization of the push pod in the anchoring mechanism.Based on the excavation load data,the excavation failure mode is studied and the coping strategy is proposed to realize the autonomy of the excavating robot.In addition,the whole process test of penetrating is carried out to verify the feasibility of inchworm drilling principle and the identification methods.Aiming at the high-density lunar soil simulants,an identification method is put forward using the least squares method and Newton iteration algorithm based on the head-cutting load model,to realize the off-line identification of high-density lunar soil objects.With the boring bit,a rotary shear test is carried out based on the Mohr-Coulomb strength theory.Two kinds of identification methods,namely SCF and CCS,according to load data feedback,are established to realize shear mech aical parameter identification for in-situ lunar soil.With the boring bit,a subsidence test is carried out based on the soil bearing pressure theory.An identification method,according to the feedback,is established to realize bearing mechaical paramet ers identification for in-situ luanr soil.Furthermore,a series of experiments are carried out based on the excavation robot to verify the feasibility of the identification methods for lunar soil mechanical parameters.Through the research of this paper,an excavation robot for large-depth lunar subsurface exploration is developed to realize parameter detection for in-situ lunar soil.Except for in-situ exploration,the robot can also serve as a platform for scientific payloads to further enrich the detection data types.The research results can provide technical support for future subsurface excavation exploration. |
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