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Drilling & coring has been selected as an effective method of acquiring soil sample in robotic planetary explorations. To avoid serious overload faults, drilling states should be monitored online and be tuned in a reasonable range. Herein, a novel flexible tube coring (FTC) method is adopted in China lunar exploration mission. To verify the proposed FTC method and acquire useful drilling states...
This paper deals with the interaction forces between robotic foot and the soft terrain, in conjunction with the Terzaghi theory. To date, some basic assumptions and conclusions for Terzaghi theory are analyzed. Terzaghi is recognized as a popular option to predict the bearing capacity of the terrain with upper structures. In this paper, static models in Terzaghi theory and its extended versions are...
Lunar soil sampling is the premise of the analysis of lunar soil and the study of lunar environment and evolutional history. Because of the restrictions of the sampling method, the size of drillers, the drilling pressure and the output power of driller, the traditional digging and vertical drilling methods can only acquire the samples from lunar surface to 3 meters deep. In order to acquire deeper...
This research proposed a pneumatic multi-pipe deep lunar soil drilling device under the background of manned lunar-landing and used coupled simulation by EDEM/Fluent for the drilled process, pneumatic drilling principle has been proved feasible by the simulation result. The drilled device this research proposed can collect lunar soil five meters under the surface, and ensure that the bedding information...
Discrete element method (DEM) is getting a wider use in granular media study. It is a fundamental of lunar soil DEM study that matching the micromechanical parameters of lunar soil simulant with its macro parameters. In this paper, the matching work is carried out by simulating triaxial test applying PFC3D software, and the constitutive model is a parallel-bonded (PB) model to match the physical characteristics...
It is presented in this paper that a novel soil drilling sampler which can be used to drill deeply automatically in the planetary soil. There are three transmission routes of motion in the drilling sampler: rotating drive mechanism and feeding drive mechanism are used to generate the rotary and axial movement of the driller respectively while impacting drive mechanism is used to assist drilling the...
Rotary-percussive Drill (RPD) has been widely employed in extraterrestrial exploration as a main drilling and sampling device. Percussive mechanism, as an inevitable part of RPD, is commonly utilized to exert percussion onto drill stem to improve drilling performance once hard rock is encountered. However, since driving resource provided by the probe is limited in lunar exploration, outputs of percussive...
The mole is an axially symmetric intrusion device, which can be treated as a carrier of different sensors that investigate the subsurface environment and properties of the material component. To some extent, the maximum penetration depth of a single stroke for hammer-driven mole is not only limited by the stroke energy but also the influence of the soil resistance which links to the shape of the front...
Drill sampling has been widely employed in extraterrestrial exploration. Since the extraterrestrial environment is uncertain and different from that on the earth, the extraterrestrial drill sampling mission is at risk of failure. Therefore, the principle of drilling and coring in extraterrestrial environment and the structural parameters of special drilling tools should be tested and verified. In...
China is endeavoring to implement the lunar exploration mission, namely Chang'e. In Phase III of the project, the aim is focusing on acquiring lunar soil sample and bringing them back to the earth. Due to the high efficiency of drilling in granular substance, a drilling and coring device is selected as the sampling tool to acquire the soil sample along the vertical direction. A novel flexible-tube...
Wheeled exploration robots are prone to slip during locomotion on deformable rough planetary terrain, which leads to loss of velocity and extra consumption of energy. Experimental results show that the power required for driving a wheel is an increasing function of its slip ratio; further, the tractive efficiency decreases rapidly after it reaches a peak value when the slip ratio is between 0.05 and...
Experimental investigation of planetary rovers' behavior requires low gravity (LG) simulation. It is true because rovers may have insufficient power to move and sink much deeper into soft soil in 1-g gravity environment. Constant-tension suspension is considered the best possible way for gravity compensation (GC) of rovers. Constant-tension cable has to be kept vertical, so tension generator mounts...
Numerical simulation analysis of the motion of wheeled mobile robots is significant for both their R&D and control phases, especially due to the recent increase in the number of planetary exploration missions. Using the position/orientation of the rover body and all the joint angles as generalized coordinates, the Jacobian matrices and recursive dynamic models are derived. Terramechanics models...
The wheel slip ratio is an important state variable in terramechanics research and the control of planetary rovers. Definitions of the slip ratio for a wheel with lugs and methods of estimating it for all wheels onboard have seldom been attempted. This paper presents several definitions for the slip ratio of a lugged wheel, which can be interconverted by altering the shearing radius. Equations for...
Identifying planetary soil parameters is not only an important scientific goal, but also necessary for exploration rover to optimize its control strategy and realize high-fidelity simulation. An improved wheel-soil interaction mechanics model is introduced, and it is then simplified by linearizing the normal stress and shearing stress to derive closed-form analytical equations. Eight unknown soil...
In order to analyze the performance of lunar rover, draw bar pull and motion resistance are analyzed in this paper based on terramechanics. The relationships between configuration parameters (like wheel width, wheel bases et al.) and mobility performance parameters are obtained from the analysis. Meanwhile, the sensitive factors of the motion resistance are found. Then main performance evaluation...
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